Correlation of treatment time to target volume for GammaPod treatments: A simple second calculation.

PURPOSE: The GammaPod is a novel device for stereotactic breast treatments that employs 25 rotating Co-60 sources while the patient is continuously translated in three axes to deliver a highly conformal dose to the target. There is no commercial software available for independent second calculations. The purpose of this study is to determine an efficient way to estimate GammaPod treatment times based on target volume and use it as a second calculation for patient-specific quality assurance. METHODS: Fifty-nine GammaPod (Xcision Medical Systems, LLC.) breast cancer patient treatments were used as the fitting dataset for this study. Similar to the Curie-seconds concept in brachytherapy, we considered dose-rate × time/(prescribed dose) as a function of target volumes. Using a MATLAB (Mathworks, Natick, MA, USA) script, we generated linear (with 95% confidence interval (CI)) and quadratic fits and tested the resulting equations on an additional set of 30 patients. RESULTS: We found a strong correlation between the dose-rate × time/(prescribed dose) and patients' target volumes for both the linear and quadratic models. The linear fit was selected for use and using the polyval function in MATLAB, a 95% CI graph was created to depict the accuracy of the prediction for treatment times. Testing the model on 30 additional patients with target volumes ranging from 20 to 188 cc yielded treatment times from 10 to 25 min that in all cases were within the predicted CI. The average absolute difference between the predicted and actual treatment times was 1.0 min (range 0-3.3 min). The average percent difference was 5.8% (range 0%-18.4%). CONCLUSION: This work has resulted in a viable independent calculation for GammaPod treatment times. This method has been implemented as a spreadsheet that is ready for clinical use to predict and verify the accuracy of breast cancer treatment times.

Reproducibility of a novel, vacuum-assisted immobilization for breast stereotactic radiotherapy.

A novel, breast-specific stereotactic radiotherapy device has been developed for delivery of highly conformal, accelerated partial breast irradiation. This device employs a unique, vacuum-assisted, breast cup immobilization system that applies a gentle, negative pressure to the target breast with the patient in the prone position. A device-specific patient loader is utilized for simulation scanning and device docking. Prior to clinical activation, a prospective protocol enrolled 25 patients who had been or were to be treated with breast conservation surgery and adjuvant radiotherapy for localized breast cancer. The patients underwent breast cup placement and two separate CT simulation scans. Surgical clips within the breast were mapped and positions measured against the device's integrated stereotactic fiducial/coordinate system to confirm reproducible and durable immobilization during the simulation, treatment planning, and delivery process for the device. Of the enrolled 25 patients, 16 were deemed eligible for analysis. Seventy-three clips (median, 4; mean, 4.6; range, 1-8 per patient) were mapped in these selected patients on both the first and second CT scans. X, Y, and Z coordinates were determined for the center point of each clip. Length of vector change in position was determined for each clip between the two scans. The mean displacement of implanted clips was 1.90 mm (median, 1.47 mm; range, 0.44-6.52 mm) (95% CI, 1.6-2.20 mm). Additional analyses stratified clips by position within the breast and depth into the immobilization cup. Overall, this effort validated the clinically utilized 3-mm planning target volume margin for accurate, reliable, and precise employment of the device.

Trends in utilization of hypofractionated whole breast irradiation (HF-WBI) in triple negative breast cancer (TNBC): a national cancer database (NCDB) analysis.

PURPOSE: We sought to identify trends over time with respect to the use of hypofractionated whole breast irradiation (HF-WBI) in women with triple negative breast cancer (TNBC) in the national cancer database (NCDB). METHODS: Trends in utilization of HF-WBI in women diagnosed with T1-2N0 TNBC in the NCDB between 2008 and 2013 were analyzed. Case-matched luminal A women were used for comparison. Variables included age, race, year of diagnosis, insurance status, income quartile, receipt of neoadjuvant chemotherapy, and institution (academic vs. community). Chi square, logistic regression, and multivariate analysis was performed. RESULTS: Utilization of HF-WBI among the 53,269 TNBC women identified steadily increased from 4.7% in 2008 to 14.0% in 2013 for women with TNBC compared to luminal A cancer whose utilization increased from 7.3 to 23.3% over the same time frame (p < 0.001). On univariate analysis, HF-WBI was associated with increasing age (p < 0.001), Medicare insurance (p < 0.001), race (p = 0.041), diagnosis after 2011 (p < 0.001), higher income quartile (p < 0.001), and treatment at academic institutions (p < 0.001). On multivariate analysis, age (p < 0.001, OR 1.038 per year), income quartile (p = 0.002, OR 1.061 per increase in quartile), treatment at an academic institution (p < 0.001, OR 1.78) significantly increased use of HF-WBI. CONCLUSIONS: Treatment at an academic center and year of diagnosis were most correlated with increased HF-WBI in T1-2N0 TNBC women in the NCDB from 2008 to 2013, followed by increasing age and income. Only 14% of T1-2N0 TNBC women received HF-WBI in 2013. Focus on increased utilization is needed for non-academic centers, lower income, and younger women.

Development and validation of a comprehensive patient-specific quality assurance program for a novel stereotactic radiation delivery system for breast lesions.

PURPOSE: The GammaPod is a dedicated prone breast stereotactic radiosurgery (SRS) machine composed of 25 cobalt-60 sources which rotate around the breast to create highly conformal dose distributions for boosts, partial-breast irradiation, or neo-adjuvant SRS. We describe the development and validation of a patient-specific quality assurance (PSQA) system for the GammaPod. METHODS: We present two PSQA methods: measurement based and calculation based PSQA. The measurements are performed with a combination of absolute and relative dose measurements. Absolute dosimetry is performed in a single point using a 0.053-cc pinpoint ionization chamber in the center of a polymethylmethacrylate (PMMA) breast phantom and a water-filled breast cup. Relative dose distributions are verified with EBT3 film in the PMMA phantom. The calculation-based method verifies point doses with a novel semi-empirical independent-calculation software. RESULTS: The average (± standard deviation) breast and target sizes were 1263 ± 335.3 cc and 66.9 ± 29.9 cc, respectively. All ion chamber measurements performed in water and the PMMA phantom agreed with the treatment planning system (TPS) within 2.7%, with average (max) difference of -1.3% (-1.9%) and -1.3% (-2.7%), respectively. Relative dose distributions measured by film showed an average gamma pass rate of 97.0 ± 3.2 when using a 3%/1 mm criteria. The lowest gamma analysis pass rate was 90.0%. The independent calculation software had average agreements (max) with the patient and QA plan calculation of 0.2% (2.2%) and -0.1% (2.0%), respectively. CONCLUSION: We successfully implemented the first GammaPod PSQA program. These results show that the GammaPod can be used to calculate and deliver the predicted dose precisely and accurately. For routine PSQA performed prior to treatments, the independent calculation is recommended as it verifies the accuracy of the planned dose without increasing the risk of losing vacuum due to prolonged waiting times.

Neutrophil-Lymphocyte Ratio Is a Prognostic Marker in Patients with Locally Advanced (Stage IIIA and IIIB) Non-Small Cell Lung Cancer Treated with Combined Modality Therapy.

BACKGROUND: Neutrophil-lymphocyte ratio (NLR) is a measure of systemic inflammation that appears prognostic in localized and advanced non-small cell lung cancer (NSCLC). Increased systemic inflammation portends a poorer prognosis in cancer patients. We hypothesized that low NLR at diagnosis is associated with improved overall survival (OS) in locally advanced NSCLC (LANSCLC) patients. PATIENTS AND METHODS: Records from 276 patients with stage IIIA and IIIB NSCLC treated with definitive chemoradiation with or without surgery between 2000 and 2010 with adequate data were retrospectively reviewed. Baseline demographic data and pretreatment peripheral blood absolute neutrophil and lymphocyte counts were collected. Patients were grouped into quartiles based on NLR. OS was estimated using the Kaplan-Meier method. The log-rank test was used to compare mortality between groups. A linear test-for-trend was used for the NLR quartile groups. The Cox proportional hazards model was used for multivariable analysis. RESULTS: The NLR was prognostic for OS (p < .0001). Median survival in months (95% confidence interval) for the first, second, third, and fourth quartile groups of the population distribution of NLR were 27 (19-36), 28 (22-34), 22 (12-31), and 10 (8-12), respectively. NLR remained prognostic for OS after adjusting for race, sex, stage, performance status, and chemoradiotherapy approach (p = .004). CONCLUSION: To our knowledge, our series is the largest to demonstrate that baseline NLR is a significant prognostic indicator in LANSCLC patients who received definitive chemoradiation with or without surgery. As an indicator of inflammatory response, it should be explored as a potential predictive marker in the context of immunotherapy and radiation therapy. IMPLICATIONS FOR PRACTICE: Neutrophil-lymphocyte ratio measured at the time of diagnosis was associated with improved overall survival in 276 patients with stage IIIA and IIIB non-small cell lung cancer (NSCLC) treated with definitive chemoradiation with or without surgery. To our knowledge, our series is the largest to demonstrate that baseline neutrophil-lymphocyte ratio is a significant prognostic indicator in locally advanced NSCLC patients who received definitive chemoradiation with or without surgery. Neutrophil-lymphocyte ratio is an inexpensive biomarker that may be easily utilized by clinicians at the time of locally advanced NSCLC diagnosis to help predict life expectancy.

Utilization of hypofractionated whole-breast radiation therapy in patients receiving chemotherapy: a National Cancer Database analysis.

PURPOSE: Results from four major hypofractionated whole-breast radiotherapy (HF-WBRT) trials have demonstrated equivalence in select patients with early-stage breast cancer when compared with conventionally fractionated WBRT (CF-WBRT). Because relatively little data were available on patients receiving neoadjuvant or adjuvant chemotherapy, consensus guidelines published in 2011 did not endorse the use of HF-WBRT in this population. Our goal is to evaluate trends in utilization of HF-WBRT in patients receiving chemotherapy. METHODS AND MATERIALS: We retrospectively analyzed data from 2004 to 2013 in the National Cancer DataBase on breast cancer patients treated with HF-WBRT who met the clinical criteria proposed by consensus guidelines (i.e., age >0 years, T1-2N0, and breast-conserving surgery), regardless of receipt of chemotherapy. We employed logistic regression to delineate and compare clinical and demographic factors associated with utilization of HF-WBRT and CF-WBRT. RESULTS: A total of 56,836 women were treated with chemotherapy and WBRT (without regional nodal irradiation) from 2004 to 2013; 9.0% (n = 5093) were treated with HF-WBRT. Utilization of HF-WBRT increased from 4.6% in 2004 to 18.2% in 2013 (odds ratio [OR] 1.21/year; P < 0.001). Among patients receiving chemotherapy, factors most dramatically associated with increased odds of receiving HF-WBRT on multivariate analysis were academic facilities (OR 2.07; P < 0.001), age >80 (OR 2.58; P < 0.001), west region (OR 1.91; P < 0.001), and distance >50 miles from cancer reporting facility (OR 1.43; P < 0.001). Factors associated with decreased odds of receiving HF-WBRT included white race, income <$48,000, lack of private insurance, T2 versus T1, and higher grade (all P < 0.02). CONCLUSIONS: Despite the absence of consensus guideline recommendations, the use of HF-WBRT in patients receiving chemotherapy has increased fourfold (absolute = 13.6%) over the last decade. Increased utilization of HF-WBRT should result in institutional reports verifying its safety and efficacy.

Increasing utilization of regional nodal irradiation in elderly node-positive women and declining emphasis on demographic factors.

PURPOSE: To evaluate the practice patterns for the use of regional nodal irradiation (RNI) in treatment of elderly women with low volume node-positive breast cancer in the setting of breast conservation surgery (BCS). METHODS: Women aged 70-89 diagnosed with unilateral, pathologic T1-2N1M0 breast cancer from 2004 to 2013, who underwent BCS and received radiotherapy were identified from the National Cancer Database. In 2011, two major trials were presented that helped define indications for RNI. Patients were dichotomized into "early", i.e. diagnosed up to 2010, and "late" cohorts. Patient and treatment characteristics were compared between the cohorts and logistic regression used to determine independent factors associated with the receipt of RNI. RESULTS: 7228 women met inclusion criteria; 4330 (59.9%) in early and 2898 (40.1%) in late cohorts. Utilization of RNI increased from 33.9% in early to 42.5% in late cohorts (P ≤ 0.001) and was independent of a general increase in RNI utilization. RNI in the early and late cohorts was not different between the study population and younger women (P > 0.05). RNI utilization increased in both cohorts with increasing number of positive lymph nodes. In the early cohort, RNI was also associated with higher grade, white race and lower income. In the late cohort, RNI increased with the presence of multiple, predefined risk factors. CONCLUSIONS: There was an increase in utilization of RNI for elderly patients from 2004 to 2013. In more recent years, the primary factors associated with receipt of RNI were tumor related with declining importance of demographic factors.

Factors Influencing Management and Outcome in Patients with Occult Breast Cancer with Axillary Lymph Node Involvement: Analysis of the National Cancer Database.

BACKGROUND: Occult breast cancer (OBC) is rare and optimal local-regional (LR) management has not been defined. Using a patient registry database, we examine factors associated with treatment and outcomes in OBC. METHODS: Female patients with cT0 N1/2 M0 BC were selected from the National Cancer Database (2004-2013) and categorized into four treatment groups: MAST = mastectomy with axillary lymph node dissection (ALND) ± radiation (RT); RT + ALND = RT with ALND, no breast surgery; ALND = ALND alone; OBS = no breast surgery, RT, or ALND. Patient characteristics and overall survival (OS) were compared between groups, and multivariable analysis was used to identify factors associated with treatment and OS. RESULTS: Among 2.03 million BC cases, 1853 females (0.09%) with cT0 N1/2 M0 disease were identified and 1231 patients were categorized into a treatment group: MAST = 592, RT + ALND = 342, ALND = 106, OBS = 191. On logistic regression, care at an academic center was associated with a higher likelihood of RT + ALND compared with MAST (odds ratio 2.03, 95% confidence interval [CI] 1.50-2.74, p < 0.001). Patients treated with RT + ALND had significantly better OS on univariate survival analysis compared with patients treated with MAST (hazard ratio [HR] 0.475, 95% CI 0.306-0.736, p = 0.001). RT + ALND was independently associated with OS on multivariable survival analysis (HR 0.509, 95% CI 0.321-0.808, p = 0.004), after adjusting for covariates. CONCLUSIONS: Patients with OBC were more likely to undergo RT + ALND if they received care at an academic center. Patients treated with RT + ALND had significantly better OS compared with patients treated with MAST, after adjusting for covariates. This supports the use of RT + ALND as LR treatment for patients with OBC.

Feasibility of CBCT-based dose with a patient-specific stepwise HU-to-density curve to determine time of replanning.

PURPOSE: (a) To investigate the accuracy of cone-beam computed tomography (CBCT)-derived dose distributions relative to fanbeam-based simulation CT-derived dose distributions; and (b) to study the feasibility of CBCT dosimetry for guiding the appropriateness of replanning. METHODS AND MATERIALS: Image data corresponding to 40 patients (10 head and neck [HN], 10 lung, 10 pancreas, 10 pelvis) who underwent radiation therapy were randomly selected. Each patient had both intensity-modulated radiation therapy and volumetric-modulated arc therapy plans; these 80 plans were subsequently recomputed on the CBCT images using a patient-specific stepwise curve (Hounsfield units-to-density). Planning target volumes (PTVs; D98%, D95%, D2%), mean dose, and V95% were compared between simulation-CT-derived treatment plans and CBCT-based plans. Gamma analyses were performed using criterion of 3%/3 mm for three dose zones (>90%, 70%~90%, and 30%~70% of maximum dose). CBCT-derived doses were then used to evaluate the appropriateness of replanning decisions in 12 additional HN patients whose plans were previously revised during radiation therapy because of anatomic changes; replanning in these cases was guided by the conventional observed source-to-skin-distance change-derived approach. RESULTS: For all disease sites, the difference in PTV mean dose was 0.1% ± 1.1%, D2% was 0.7% ± 0.1%, D95% was 0.2% ± 1.1%, D98% was 0.2% ± 1.0%, and V95% was 0.3% ± 0.8%; For 3D dose comparison, 99.0% ± 1.9%, 97.6% ± 4.4%, and 95.3% ± 6.0% of points passed the 3%/3 mm criterion of gamma analysis in high-, medium-, and low-dose zones, respectively. The CBCT images achieved comparable dose distributions. In the 12 previously replanned 12 HN patients, CBCT-based dose predicted well changes in PTV D2% (Pearson linear correlation coefficient = 0.93; P < 0.001). If 3% of change is used as the replanning criteria, 7/12 patients could avoid replanning. CONCLUSIONS: CBCT-based dose calculations produced accuracy comparable to that of simulation CT. CBCT-based dosimetry can guide the decision to replan during the course of treatment.

A Prospective Trial of Single-Fraction Radiation to the Tumor Bed with a Novel Breast-Specific Stereotactic Radiation Therapy Device: The GammaPod.

Purpose: Radiation therapy for early-stage breast cancer is typically delivered in a hypofractionated regimen to the whole breast followed by a tumor bed boost. This results in a treatment course of approximately 4 weeks. In this study, the tumor bed boost was delivered in a single fraction as part of a safety and feasibility study for FDA clearance of the device. Methods and Materials: Eligible women with early-stage breast cancer underwent lumpectomy followed by radiation therapy. Patients underwent breast immobilization using a system specific to the GammaPod followed by CT simulation, boost treatment planning, and boost treatment delivery all in a single treatment day. Patients then started whole-breast radiation therapy within 1 week of the boost treatment. Patients and treatments were assessed for safety and feasibility. Acute toxicities were recorded. Results: A single-fraction boost of 8 Gy was delivered to the tumor bed before a course of whole-breast radiation. The GammaPod treatment was successfully delivered to 14 of 17 enrolled patients. Acute toxicities from all radiation therapy, inclusive of the boost and whole-breast radiation, were limited to grade 1 events. Conclusions: The GammaPod device successfully delivered a single-fraction boost treatment to the tumor bed with no change in expected acute toxicities. The results of this study led to FDA clearance of the device through the Investigational Device Exemption process at the FDA. The GammaPod is in clinical use at 4e institutions nationally and internationally, with additional sites pending in 2023.

Partial Breast Irradiation for Patients With Early-Stage Invasive Breast Cancer or Ductal Carcinoma In Situ: An ASTRO Clinical Practice Guideline.

PURPOSE: This guideline provides evidence-based recommendations on appropriate indications and techniques for partial breast irradiation (PBI) for patients with early-stage invasive breast cancer and ductal carcinoma in situ. METHODS: ASTRO convened a task force to address 4 key questions focused on the appropriate indications and techniques for PBI as an alternative to whole breast irradiation (WBI) to result in similar rates of ipsilateral breast recurrence (IBR) and toxicity outcomes. Also addressed were aspects related to the technical delivery of PBI, including dose-fractionation regimens, target volumes, and treatment parameters for different PBI techniques. The guideline is based on a systematic review provided by the Agency for Healthcare Research and Quality. Recommendations were created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength. RESULTS: PBI delivered using 3-dimensional conformal radiation therapy, intensity modulated radiation therapy, multicatheter brachytherapy, and single-entry brachytherapy results in similar IBR as WBI with long-term follow-up. Some patient characteristics and tumor features were underrepresented in the randomized controlled trials, making it difficult to fully define IBR risks for patients with these features. Appropriate dose-fractionation regimens, target volume delineation, and treatment planning parameters for delivery of PBI are outlined. Intraoperative radiation therapy alone is associated with a higher IBR rate compared with WBI. A daily or every-other-day external beam PBI regimen is preferred over twice-daily regimens due to late toxicity concerns. CONCLUSIONS: Based on published data, the ASTRO task force has proposed recommendations to inform best clinical practices on the use of PBI.

Validation of Patient-Reported Outcomes in Patients With Nonmetastatic Breast Cancer Receiving Comprehensive Nodal Irradiation in the RadComp Trial.

PURPOSE: Our purpose was to evaluate the measurement properties of patient-reported outcome (PRO) measures used in the ongoing RadComp pragmatic randomized clinical trial (PRCT). METHODS AND MATERIALS: The deidentified and blinded data set included 774 English-speaking female participants who completed their 6-month posttreatment assessment. Eleven PRO measures were evaluated, including the Trial Outcome Index from the Functional Assessment of Cancer Therapy-Breast (FACT-B), Satisfaction with Breast Cosmetic Outcomes, the BREAST-Q, and selected Patient-Reported Outcomes Measurement Information System (PROMIS) measures. PROs were measured at 3 timepoints: baseline, completion of radiation therapy (RT), and 6 months post-RT. Ten variables were used as validity anchors. Pearson or Spearman correlations were calculated between PROs and convergent validity indicators. Mean PRO differences between clinically distinct categories were compared with analysis of variance methods (known-groups validity). PRO change scores were mapped to change in other variables (sensitivity to change). RESULTS: Most correlations between PROs and validity indicators were large (≥0.5). Mean score for Satisfaction with Breast Cosmetic Outcomes was higher (better) for those with a lumpectomy compared with those with a mastectomy (P < .001). Mean scores for the FACT-B Trial Outcome Index and for PROMIS Fatigue and Ability to Participate in Social Roles and Activities were better for those with good baseline performance status compared with those with poorer baseline performance status (P < .05). At completion of RT and post-RT, mean scores for Satisfaction with Breast Cosmetic Outcomes and BREAST-Q Radiation were significantly different (P < .001) across categories for all Functional Assessment of Chronic Illness Therapy -Treatment Satisfaction - General items. There were medium-sized correlations between change scores for FACT-B Trial Outcome Index, Fatigue, Anxiety, and Ability to Participate in Social Roles and change scores in the Visual Analog Scale. CONCLUSIONS: For patients with nonmetastatic breast cancer receiving radiation in the RadComp PRCT, our findings demonstrate high reliability and validity for important PRO measures, supporting their psychometric strength and usefulness to reflect the effect of RT on health-related quality of life.

Clinical Outcomes of Intensity Modulated Proton Therapy Reirradiation for Gynecologic Malignancies.

Purpose: Pelvic reirradiation (re-RT) for patients with gynecologic cancers remains a challenge because of toxicity concerns. Given the dosimetric advantages of proton therapy, we aimed to assess oncologic and toxicity outcomes of patients with re-RT to the pelvis/abdomen with intensity modulated proton therapy (IMPT) for gynecologic cancers. Methods and Materials: We performed a retrospective analysis of all patients with gynecologic cancer treated at a single institution between 2015 and 2021 with IMPT re-RT. Patients were included for analysis if the IMPT plan had at least partial overlap with the treated volume of a previous radiation treatment. Results: A total of 29 patients were included for analysis, with 30 total courses of re-RT. The majority of patients had been treated previously with conventional fractionation to a median dose of 49.2 Gy (30-61.6 Gy). With a median follow-up of 23 months, 1-year local control was 83.5% and overall survival was 65.7%. Three patients (10%) developed acute and late grade 3 toxicity. One-year freedom from late grade 3+ toxicity was 96.3%. Conclusions: This is the first complete analysis of clinical outcomes for re-RT with IMPT for gynecologic malignancies. We demonstrate excellent local control and acceptable acute and late toxicity. IMPT should strongly be considered for treatments requiring re-RT for gynecologic malignancies.

Proton Arc Therapy vs Interstitial HDR Brachytherapy in Gynecologic Cancer with Parametrial/pelvic Side Wall Extension.

Purpose: To investigate whether volumetric-modulated proton arc therapy (VPAT) plans generate comparable doses to organs at risk (OARs) compared with interstitial high-dose-rate (iHDR) brachytherapy for patients with gynecologic cancer with disease extension to parametrial/pelvic side wall, who are not eligible for the aggressive procedure. Materials and Methods: VPAT delivers proton arc beams by modulated energies at the beam nozzle while maintaining the same incident energy to the gantry during the arc rotation. Plans of 10 patients previously treated with iHDR brachytherapy for high-risk clinical treatment volumes (HRCTV; 31.8-110.6 cm3; lateral dimensions, 4.2-5.6 cm) were selected and compared with VPAT plans. VPAT plans for each patient were designed using a 152- to 245-MeV range of energy-modulated proton beams. Results: HRCTV coverage of the VPAT plans was comparable to that of the iHDR plans, with V150% showing no statistical differences. On average, the V100% and V90% of VPAT plans were higher than those of the iHDR plans, 95.0% vs 91.9% (P = .02) and 98.6% vs 97.5% (P = .02), respectively. D100 was also 17% higher for the VPAT plans (P = .03). On average, the D2cm3 of bladder, rectum, and small bowels in the VPAT plans were considerably lower than those in iHDR plans (by 17.4%, 35.2%, and 65.6%, respectively; P < .05 for all OARs). Conclusion: VPAT-generated plans were dosimetrically superior to those with HDR brachytherapy with interstitial needles for locally advanced gynecologic cancer with parametrial/pelvic side wall disease extension. Dosimetrically, VPAT provides a noninvasive alternative to iHDR brachytherapy with a superior dosimetric profile.

Intensity Modulated Proton Therapy Treatment Planning for Postmastectomy Patients with Metallic Port Tissue Expanders.

PURPOSE: Proton beam therapy can significantly reduce cardiopulmonary radiation exposure compared with photon-based techniques in the postmastectomy setting for locally advanced breast cancer. For patients with metallic port tissue expanders, which are commonly placed in patients undergoing a staged breast reconstruction, dose uncertainties introduced by the high-density material pose challenges for proton therapy. In this report, we describe an intensity modulated proton therapy planning technique for port avoidance through a hybrid single-field optimization/multifield optimization approach. METHODS AND MATERIALS: In this planning technique, 3 beams are utilized. For each beam, no proton spot is placed within or distal to the metal port plus a 5 mm margin. Therefore, precise modeling of the metal port is not required, and various tissue expander manufacturers/models are eligible. The blocked area of 1 beam is dosimetrically covered by 1 or 2 of the remaining beams. Multifield optimization is used in the chest wall target region with blockage of any beam, while single-field optimization is used for remainder of chest wall superior/inferior to the port. RESULTS: Using this technique, clinical plans were created for 6 patients. Satisfactory plans were achieved in the 5 patients with port-to-posterior chest wall separations of 1.5 cm or greater, but not in the sixth patient with a 0.7 cm separation. CONCLUSIONS: We described a planning technique and the results suggest that the metallic port-to-chest wall distance may be a key parameter for optimal plan design.

Perceptions and Patterns in Academic Publishing: A Survey of United States Residents in Radiation Oncology.

PURPOSE: We aimed to assess perceptions of, and training regarding, the publishing process among US radiation oncology (RO) residents, focusing on awareness and understanding of criteria for selecting appropriate and legitimate peer-reviewed journals for academic publishing. The growing challenge of predatory publication in the broader scientific realm and its relevancy to resident training is also briefly discussed. METHODS AND MATERIALS: A survey was opened to residents of all Accreditation Council for Graduate Medical Education-accredited RO programs in the United States, focusing on 3 categories: (1) demographics; (2) submission, peer review, and publication of academic research; and (3) subjective ranking of factors for choosing an appropriate publisher/journal. Results were stratified by level of training and number of publications. RESULTS: Overall, 150 of 690 residents (19.8%) responded, with a 98% (147 of 150) completion rate. Twenty of 150 residents (13.3%) reported formal training in manuscript preparation and choosing academic journals. Only 3.4% of residents reported departmental guidelines regarding publication in "predatory" journals; 57.7% were unsure. The 3 most important factors influencing publisher and journal choice were impact factor (ranked first for 59.0%), whether a journal is found in a major index (ranked first for 18.0%), and association with a reputable organization (ranked first for 17.0%). Importance of impact factor increased with number of publications (50% with 0 publications, 48.3% with 1-5, 63.9% with 5-10, 76.2% with 10-15, and 70.6% with >15). Cost considerations influenced journal choice at least once for 79 (52.7%) residents. CONCLUSIONS: Impact factor was the most important consideration for residents when choosing an appropriate publisher, with increased emphasis with increasing number of publications. A minority had formal training in choosing appropriate academic journals and knowing how to identify so-called predatory journals or were aware if their department has proscriptions regarding publication in such journals. Additional emphasis on formal training for RO residents in manuscript preparation and choosing academic journals is warranted.

Dosimetry evaluation of the GammaPod stereotactic radiosurgery device based on established AAPM and IAEA protocols.

PURPOSE: The GammaPod is a novel dedicated prone breast stereotactic radiosurgery (SRS) device recently developed at the University of Maryland Medical Center. This device utilizes multiple rotating Co-60 sources to create highly conformal dose distributions for breast treatments, including boosts, partial breast irradiation, or presurgery SRS. However, due to its small field sizes and nonstandard geometry, existing calibration protocols cannot be directly applied. In this study, we adapt and implement the American Association of Physicists in Medicine Task Group 21 (TG-21) and International Atomic Energy Agency (IAEA) Technical Report Series 483 (TRS 483) protocols for reference dose measurements for the GammaPod. This represents the first published dosimetric investigation GammaPod and is meant to serve as a reference to future users commissioning and calibrating these devices. METHODS: Reference dose measurements were performed following the TG-21/IAEA TRS 483 protocols using an ADCL-calibrated Exradin A1SL thimble chamber in a polymethyl methacrylate (PMMA) breast-mimicking phantom. Monte Carlo calculations and measurements were also performed in water to determine chamber-specific k PMMA Q m s r , Q 0 f msr , f ref quality conversion factor converting reference field size (fref ) to machine-specific field sizes (fmsr ) (25-mm) as well as k PMMA f clin , f msr , the conversion factor from the (fmsr ) to the clinical field size (fclin ) (15mm). Verification was performed using the thermoluminescent dosimeter remote monitoring service from the Imaging and Radiation Oncology Core (IROC) in Houston, TX. RESULTS: The (fref ) to (fmsr ) chamber-specific factor k PMMA Q m s r , Q 0 f msr , f ref was 0.992 while the (fmsr ) to (fclin ) chamber-specific k PMMA f clin , f msr factor was 1.014. The radiation absorbed dose to water measured in the PMMA phantom based on the TG-21/IAEA TRS 483 formalism agreed with IROC values to within 1% and 2% for the 25- and 15-mm collimators, respectively. CONCLUSION: We successfully implemented the TG-21 and TRS 483 reference dosimetry protocols for the GammaPod. These results show agreement between measurements performed with different reference dosimetry protocols and independent thermoluminescent measurements.

Optimal Target Delineation and Treatment Techniques in the Era of Conformal Photon and Proton Breast and Regional Nodal Irradiation.

PURPOSE: Regional nodal irradiation improves disease-free and distant disease-free survival in patients with high-risk breast cancer (BC). Trials demonstrating this used 2- or 3-dimensional conformal radiation therapy (2-dimensional or 3-dimensional [3D] conformal radiotherapy [CRT]) fields based on bony anatomy. Modern volumetric-modulated arc therapy (VMAT) and pencil beam scanning proton therapy (PBSPT) may underdose regional nodes (RNs) not contoured but covered by 3D CRT. Multiple atlases guide modern treatment planning. This study addresses the risk of underdosing when relying on published atlases and treating with 3D CRT, VMAT, and PBSPT. METHODS AND MATERIALS: Targets per the Radiation Therapy Oncology Group (RTOG), European Society for Radiotherapy and Oncology (ESTRO), and Radiotherapy Comparative Effectiveness Consortium (RADCOMP) atlases were contoured on a representative patient CT scan. 3D CRT plans based on anatomic borders and VMAT and PBSPT plans for each set of target volumes were generated. Positron emission tomography/computed tomography (PET/CT) scans were reviewed. CT-positive and 18F-fluorodeoxyglucose (18F-FDG)-avid RNs (n = 389) were mapped from 102 patients with locally advanced (n = 51; median 2; range, 1-8 nodes) and metastatic (n = 51; median 4; range, 1-19 nodes) BC: axillary (AX; n = 284), supraclavicular (SCV; n = 60), and internal mammary nodal (IMN; n = 45). 18F-FDG-avid RNs falling within the 95% isodose line were considered adequately covered. RESULTS: 3D CRT plans provided excellent RN coverage. Low AX nodes were covered (≥99%) in all plans. Underdosing of 18F-FDG-avid RNs falling in the high AX (78%-92%), SCV (52%-75%), and IMN (84%-89%) volumes was observed following the RTOG and ESTRO atlases for VMAT and PBSPT plans. Use of the RADCOMP atlas provided coverage of these areas (89%-100%) with slightly increased heart and lung doses. Atlas guided VMAT/PBSPT plans provided cumulative nodal coverage as follows: ESTRO (89%/88%), RTOG (93%/91%), and RADCOMP (98%/96%). CONCLUSIONS: VMAT and PBSPT for regional nodal irradiation in patients with high-risk BC risks underdosage in the high AX, SCV, and IMN nodal regions unless comprehensive target delineation is performed.

Techniques for Treating Bilateral Breast Cancer Patients Using Pencil Beam Scanning Technology.

PURPOSE: Patients with bilateral breast cancer (BBC), who require postmastectomy radiation therapy or radiation as part of breast conservation treatment, present a unique technical challenge. Even with modern techniques, such as intensity modulated radiation therapy or volumetric modulated arc therapy (VMAT), adequate target coverage is rarely achieved without the expense of increased integral dose to important organs at risk (OARs), such as the heart and lungs. Therefore, we present several BBC techniques and a treatment algorithm using intensity-modulated proton therapy (IMPT) for patients treated at our center. MATERIALS AND METHODS: We describe 3 different BBC treatment techniques using IMPT on patients treated at our center, with comparison VMAT plans to demonstrate the dosimetric benefit of proton therapy in these patients. Following RADCOMP (Radiation Therapy Oncology Group, Philadelphia, Pennsylvania) guidelines, a single physician approved all target volumes and OARs. Plans were designed so that ≥ 95% of the prescribed dose covered ≥ 95% of all targets. Parameters for dosimetric volume histograms for the clinical targets and OARs are reported for the 2 radiation methods. RESULTS: All methods demonstrated acceptable target coverage with 95% of the prescription planning target volume reaching a mean (± SD) of 98.0% (± 0.87%) and 97.5% (± 2.39%), for VMAT and IMPT plans, respectively. Conformity and homogeneity were also similar between the 2 techniques. Proton therapy provided observed improvements in mean heart dose (average heart mean [SD], 9.98 Gy [± 0.87 Gy] versus 2.12 Gy [± 0.96 Gy]) and total lung 5% prescription dose (V5; mean [SD] total lung V5, 97.9% [± 2.84%]), compared with 39.8% [± 9.39%]). All IMPT methods spared critical OARs; however, the single, 0° anterior-posterior plan allowed for the shortest treatment time. CONCLUSION: Both VMAT and all 3 IMPT techniques provided excellent target coverage in patients with BBC; however, proton therapy was superior in decreasing the dose to OARs. A single-field optimization approach should be the IMPT method of choice when feasible.

Preserving Endocrine Function in Premenopausal Women Undergoing Whole Pelvis Radiation for Cervical Cancer.

PURPOSE: Whole pelvis radiation therapy (WPRT) in premenopausal women with cervical cancer can cause permanent ovarian damage, resulting in premature menopause. Oophoropexy, often considered as an initial step, demonstrates safety of sparing 1 ovary at the cost of delay in initiating WPRT. Therefore, we dosimetrically compared volumetric modulated arc radiotherapy (VMAT) and intensity modulated proton therapy (IMPT) techniques to allow for ovarian-sparing WPRT. MATERIALS AND METHODS: Ten patients previously treated for cervical cancer at our institution were included in this institutional review board-approved analysis. A modified clinical treatment volume (CTV) was designed, sparing 1 ovary (left or right), as determined by the physician (ovarian-sparing CTV) and disease extent, including physical exam, positron emission tomography/computed tomography and magnetic resonance imaging. An ovarian-sparing planning target volume was determined as the ovarian-sparing CTV+5 mm for patients who were supine and 7 mm for those who were prone. All plans were calculated to a dose of 45 Gy with specific optimization goals for target volumes, while attempting to maintain a mean ovary dose (Dmean) < 15 Gy. Dosimetric goals were compared across the 2 modalities using the Mann-Whitney U test. RESULTS: Both treatment modalities were able to achieve primary clinical goal coverage to the uterus/cervix (P = .529, comparing VMAT versus IMPT), ovarian-sparing CTV (P = .796) and ovarian-sparing planning target volume (P = .004). All 10 IMPT plans were able to accomplish the ovary objective (14.0 ± 1.66 Gy). However, only 4 of the 10 VMAT plans were able to achieve a Dmean < 15 Gy to the prioritized ovary, with an average dose of 15.3 ± 4.10 Gy. CONCLUSION: Sparing an ovary in women undergoing WPRT for cervical cancer is dosimetrically feasible with IMPT without sacrificing coverage to important clinical targets. Future work will incorporate the brachytherapy dose to the ovarian-sparing CTV and assess the clinical response of this technique as a means to preserve ovarian endocrine function.