The National Cancer Institute's Cancer Disparities Research Partnership Program: a unique funding model 20 years later.

The burden of cancer and access to effective treatment are not experienced equally by all in the United States. For underserved populations that often access the health-care system when their cancers are in advanced disease stages, radiation oncology services are essential. In 2001, the National Cancer Institute's (NCI's) Radiation Research Program created and implemented the Cancer Disparities Research Partnership Program (CDRP). CDRP was a pioneering funding model whose goal was to increase participation of medically underserved populations in NCI clinical trials. CDRP's Cooperative Agreement funding supported for awardees the planning, development, and conduct of radiation oncology clinical research in institutions not traditionally involved in NCI-sponsored research and cared for a disproportionate number of medically underserved, health-disparities populations. The awardee secured and provided support for mentorship from 1 of 2 NCI comprehensive cancer centers named in its application. Six CDRP awards were made over two 5-year funding periods ending in 2013, with the end-of-program accomplishments previously reported. With the current focus on addressing equity, diversity, and inclusion, the 6 principal investigators were surveyed, 5 of whom responded about the impact of CDRP on their institutions, communities, and personal career paths. The survey that was emailed included 10 questions on a 5-point Likert scale. It was not possible to collect patient data this long after completion of the program. This article provides a 20-year retrospective of the experiences and observations from those principal investigators that can inform those now planning, building, and implementing equity, diversity, and inclusion programs.

Phase I Trial of Cetuximab, Radiotherapy, and Ipilimumab in Locally Advanced Head and Neck Cancer.

PURPOSE: Concurrent radiotherapy with cetuximab, an anti-EGFR mAb, is a standard treatment for locally advanced head and neck squamous carcinoma (HNSCC). Cytotoxic T lymphocyte antigen-4-positive (CTLA-4+) regulatory T cells (Treg) dampen cellular immunity and correlate negatively with clinical outcomes. This phase I study added ipilimumab, an anti-CTLA-4 mAb, to cetuximab-radiotherapy. PATIENTS AND METHODS: A (3 + 3) design was used to establish the recommended phase II dose (RP2D) of ipilimumab, added at week 5 for four, every-3-week doses to fixed, standard cetuximab-radiotherapy. Eligible subjects had stage III to IVb, high-risk [human papillomavirus-negative (HPV-)] or intermediate-risk HPV-positive (HPV+)] HNSCC. Dose-limiting toxicity (DLT) was defined as any grade 4 adverse event (AE) except in-field radiation dermatitis or immune-related (ir) AE requiring ≥2 weeks of systemic steroids. Baseline tumor and serial blood specimens were collected for immune correlatives. RESULTS: From July 2013 to May 2016, 18 patients enrolled. Two of 6 in cohort 1 (ipilimumab 3 mg/kg) experienced grade 3 dermatologic DLTs, triggering deescalation of ipilimumab to 1 mg/kg. Dose level -1 was expanded to N = 12 without DLT. irAE included: grade 1, 2, and 3 dermatitis (2, 1, and 3 cases), grade 4 colitis (1), and grade 1 hyperthyroidism (1). Three-year disease-free survival (DFS) and overall survival were 72% [90% confidence interval (CI), 57-92] and 72% (90% CI, 56-92). High expression of coinhibitory receptors PD1/LAG3/CD39 on baseline tumor-infiltrating Treg was associated with worse DFS (HR = 5.6; 95% CI, 0.83-37.8; P = 0.08). CONCLUSIONS: The RP2D for ipilimumab plus standard cetuximab-radiotherapy is 1 mg/kg in weeks 5, 8, 11, and 14. The regimen is tolerable and yields acceptable survival without cytotoxic chemotherapy.

Initial Data Pooling for Radiation Dose-Volume Tolerance for Carotid Artery Blowout and Other Bleeding Events in Hypofractionated Head and Neck Retreatments.

PURPOSE: Dose-volume data for injury to carotid artery and other major vessels in stereotactic body radiation therapy (SBRT)/SABR head and neck reirradiation were reviewed, modeled, and summarized. METHODS AND MATERIALS: A PubMed search of the English-language literature (stereotactic and carotid and radiation) in April 2018 found 238 major vessel maximum point doses in 6 articles that were pooled for logistic modeling. Two subsequent studies with dose-volume major vessel data were modeled separately for comparison. Attempts were made to separate carotid blowout syndrome from other bleeding events (BE) in the analysis, but we acknowledge that all except 1 data set has some element of BE interspersed. RESULTS: Prior radiation therapy (RT) dose was not uniformly reported per patient in the studies included, but a course on the order of conventionally fractionated 70 Gy was considered for the purposes of the analysis (with an approximately ≥6-month estimated interval between prior and subsequent treatment in most cases). Factors likely associated with reduced risk of BE include nonconsecutive daily treatment, lower extent of circumferential tumor involvement around the vessel, and no surgical manipulation before or after SBRT. CONCLUSIONS: Initial data pooling for reirradiation involving the carotid artery resulted in 3 preliminary models compared in this Hypofractionated Treatment Effects in the Clinic (HyTEC) report. More recent experiences with alternating fractionation schedules and additional risk-reduction strategies are also presented. Complications data for the most critical structures such as spinal cord and carotid artery are so limited that they cannot be viewed as strong conclusions of probability of risk, but rather, as a general guideline for consideration. There is a great need for better reporting standards as noted in the High Dose per Fraction, Hypofractionated Treatment Effects in the Clinic introductory paper.

Tumor Control Probability of Radiosurgery and Fractionated Stereotactic Radiosurgery for Brain Metastases.

PURPOSE: As part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, tumor control probability (TCP) after stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) for brain metastases was modeled based on pooled dosimetric and clinical data from published English-language literature. METHODS AND MATERIALS: PubMed-indexed studies published between January 1995 and September 2017 were used to evaluate dosimetric and clinical predictors of TCP after SRS or fSRS for brain metastases. Eligible studies had ≥10 patients and included detailed dose-fractionation data with corresponding ≥1-year local control (LC) data, typically evaluated as a >20% increase in diameter of the targeted lesion using the pre-SRS diameter as a reference. RESULTS: Of 2951 potentially eligible manuscripts, 56 included sufficient dose-volume data for analyses. Accepting that necrosis and pseudoprogression can complicate the assessment of LC, for tumors ≤20 mm, single-fraction doses of 18 and 24 Gy corresponded with >85% and 95% 1-year LC rates, respectively. For tumors 21 to 30 mm, an 18 Gy single-fraction dose was associated with 75% LC. For tumors 31 to 40 mm, a 15 Gy single-fraction dose yielded ∼69% LC. For 3- to 5-fraction fSRS using doses in the range of 27 to 35 Gy, 80% 1-year LC has been achieved for tumors of 21 to 40 mm in diameter. CONCLUSIONS: TCP for SRS and fSRS are presented. For small lesions ≤20 mm, single doses of ≈18 Gy appear generally associated with excellent rates of LC; for melanoma, higher doses seem warranted. For larger lesions >20 mm, local control rates appear to be ≈ 70% to 75% with usual doses of 15 to 18 Gy, and in this setting, fSRS regimens should be considered. Greater consistency in reporting of dosimetric and LC data is needed to facilitate future pooled analyses. As systemic and biologic therapies evolve, updated analyses will be needed to further assess the necessity, efficacy, and toxicity of SRS and fSRS.

Maximizing Tumor Control and Limiting Complications With Stereotactic Body Radiation Therapy for Pancreatic Cancer.

PURPOSE: Stereotactic body radiation therapy (SBRT) and stereotactic ablative body radiation therapy is being increasingly used for pancreatic cancer (PCa), particularly in patients with locally advanced and borderline resectable disease. A wide variety of dose fractionation schemes have been reported in the literature. This HyTEC review uses tumor control probability models to evaluate the comparative effectiveness of the various SBRT treatment regimens used in the treatment of patients with localized PCa. METHODS AND MATERIALS: A PubMed search was performed to review the published literature on the use of hypofractionated SBRT (usually in 1-5 fractions) for PCa in various clinical scenarios (eg, preoperative [neoadjuvant], borderline resectable, and locally advanced PCa). The linear quadratic model with α/ß= 10 Gy was used to address differences in fractionation. Logistic tumor control probability models were generated using maximum likelihood parameter fitting. RESULTS: After converting to 3-fraction equivalent doses, the pooled reported data and associated models suggests that 1-year local control (LC) without surgery is ≈79% to 86% after the equivalent of 30 to 36 Gy in 3 fractions, showing a dose response in the range of 25 to 36 Gy, and decreasing to less than 70% 1-year LC at doses below 24 Gy in 3 fractions. The 33 Gy in 5 fraction regimen (Alliance A021501) corresponds to 28.2 Gy in 3 fractions, for which the HyTEC pooled model had 77% 1-year LC without surgery. Above an equivalent dose of 28 Gy in 3 fractions, with margin-negative resection the 1-year LC exceeded 90%. CONCLUSIONS: Pooled analyses of reported tumor control probabilities for commonly used SBRT dose-fractionation schedules for PCa suggests a dose response. These findings should be viewed with caution given the challenges and limitations of this review. Additional data are needed to better understand the dose or fractionation-response of SBRT for PCa.

Head and Neck Tumor Control Probability: Radiation Dose-Volume Effects in Stereotactic Body Radiation Therapy for Locally Recurrent Previously-Irradiated Head and Neck Cancer: Report of the AAPM Working Group.

PURPOSE: Stereotactic body radiation therapy (SBRT) has emerged as a viable reirradiation strategy for locally recurrent previously-irradiated head and neck cancer. Doses in the literature have varied, which challenges clinical application of SBRT as well as clinical trial design. MATERIAL & METHODS: A working group was formed through the American Association of Physicists in Medicine to study tumor control probabilities for SBRT in head and neck cancer. We herein present a systematic review of the available literature addressing the dose/volume data for tumor control probability with SBRT in patients with locally recurrent previously-irradiated head and neck cancer. Dose-response models are generated that present tumor control probability as a function of dose. RESULTS: Data from more than 300 cases in 8 publications suggest that there is a dose-response relationship, with superior local control and possibly improved overall survival for doses of 35 to 45 Gy (in 5 fractions) compared with <30 Gy. CONCLUSION: Stereotactic body radiation therapy doses equivalent to 5-fraction doses of 40 to 50 Gy are suggested for retreatment.

Dose-response model for severe late laryngeal toxicity after stereotactic body radiation therapy for previously-irradiated head and neck cancer.

We sought to evaluate the association between larynx dose and risk of severe late laryngeal toxicity in patients undergoing re-irradiation SBRT for recurrent HNC. Fifty-five patients with an intact larynx underwent re-irradiation SBRT to a median dose of 44 Gy in 5 fractions. Five (41.7%) patients treated for a laryngeal/hypopharyngeal recurrence experienced late grade ≥3 laryngeal toxicity, compared to 0.0-7.1% for other sites. Logistic dose-response models were created to predict risk of severe late laryngeal toxicity, including dysphagia and airway compromise. According to the model, the risk of severe laryngeal toxicity with a larynx D5cc of 5 Gy is 5.8% (95% CI 2.9-9.9%) and rises to 11.4% with a D5cc of 20 Gy and 25.3% with a D5cc of 40 Gy. In patients with a laryngeal/hypopharyngeal recurrence, SBRT planning should carefully assess the dose to laryngeal structures given these dose findings, and SBRT should be approached with significant caution in such patients.

Patterns of Failure After Adjuvant Stereotactic Body Radiation Therapy for Pancreatic Cancer With Close or Positive Margins.

PURPOSE: There is no consensus on treatment volumes for adjuvant stereotactic body radiation therapy (SBRT) for pancreatic cancer. Herein, we report patterns of failure after pancreatic SBRT for close/positive margins, which may inform target volume design. METHODS AND MATERIALS: An institutional review board-approved retrospective review of patients with pancreatic adenocarcinoma treated with adjuvant SBRT for close/positive margins from 2009 to 2018 was conducted. Patterns of failure were defined as local (LF) within the tumor bed, regional (RF) within lymph nodes or anastomoses, or distant (DF). The cumulative incidence of locoregional failure was calculated using the cumulative incidence function accounting for the competing risk of death. LFs were mapped to the planning target volume (PTV) and classified as in-field (completely within the PTV), marginal (partially within the PTV), or out-of-field (completely outside the PTV). The location of LFs was compared with the Radiation Therapy Oncology Group 0848 contouring atlas to determine whether standard postoperative radiation therapy volumes would have included the LF. RESULTS: Seventy-six patients were treated with adjuvant SBRT for close (51.3%) or positive (48.7%) margins. Most (81.6%) received 36 Gy in 3 fractions, with a median PTV volume of 17.8 cc (interquartile range, 12.1-25.6). With a median follow-up of 17.0 months (interquartile range, 7.3-28.4), crude rates of first isolated LF, isolated RF, and DF +/- LF or RF were 9.2%, 6.6%, and 56.6%, respectively. Two-year cumulative incidences of LF, RF, locoregional failure, and DF were 34.9%, 30.8%, 49.2%, and 60.4%, respectively. Of 28 reviewable LFs, 21.4% were in-field while the remainder were completely outside (60.7%) or partially outside (17.9%) the PTV. Most LFs (92.9%) would have been encompassed by the Radiation Therapy Oncology Group consensus target volumes. CONCLUSIONS: After adjuvant pancreatic SBRT for close/positive margins, the majority of LFs were outside the PTV but within contemporary target volumes for conventional radiation therapy.

Radiation oncologists' attitudes and beliefs about intensity-modulated radiation therapy and stereotactic body radiation therapy for prostate cancer.

BACKGROUND: To better understand how radiation oncologists perceive intensity-modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) for prostate cancer and how these perceptions may influence treatment decisions. METHODS: We conducted semi-structured interviews of radiation oncologists between January-May, 2016. We used a purposeful sampling technique to select participants across a wide range of experience, regions, and practice types. Two trained qualitative researchers used an inductive, iterative approach to code transcripts and identify themes. We then used content analysis and thematic analysis of the coded transcripts to understand radiation oncologists' attitudes and beliefs about IMRT and SBRT. RESULTS: Thematic saturation was achieved after 20 interviews. Participants were affiliated with academic (n = 13; 65%), private (n = 5; 25%), and mixed (n = 2; 10%) practices and had a wide range of clinical experience (median 19 years; range 4-49 years). Analysis of interview transcripts revealed four general themes: 1) most radiation oncologists offered surgery, brachytherapy, IMRT, and active surveillance for low-risk patients; 2) there was no consensus on the comparative effectiveness of IMRT and SBRT; 3) key barriers to adopting SBRT included issues related to insurance, reimbursement, and practice inertia; and 4) despite these barriers, most participants envisioned SBRT use increasing over the next 5-10 years. CONCLUSIONS: In the absence of strong opinions about effectiveness, nonclinical factors influence the choice of radiation treatment. Despite a lack of consensus, most participants agreed SBRT may become a standard of care in the future.

Long-Term Patient-Reported Quality of Life After Stereotactic Body Radiation Therapy for Recurrent, Previously-Irradiated Head and Neck Cancer.

Objectives: Long-term quality-of-life data following stereotactic body radiation therapy (SBRT) for recurrent head and neck cancer (rHNC) is underreported. We report patient-reported quality-of-life (PR-QOL) after at least 1 year post-treatment. Methods and Materials: A retrospective review was performed on 64 patients receiving SBRT for previously-irradiated rHNC. PR-QOL was prospectively evaluated using the University of Washington Quality of Life Questionnaire. The mixed effects proportional odds model was used to assess post-treatment overall PR-QOL changes, as well as the effects of late toxicities, tumor volume > 25 cc, local failure, nodal recurrence, distant failure, prior neck dissection, performance status other than ECOG 0 or Karnofsky 100, sex, age >65, squamous vs. non-squamous primary histology, and specific organ recurrence. Results: SBRT had no significant effect on overall PR-QOL at days 1-90 post-treatment (SBRT effect 0.035, p = 0.93) and days 91-365 (SBRT effect -0.30, p = 0.45). Beyond day 365, overall PR-QOL was significantly worse than baseline (SBRT effect -0.77, p =.03). Grade ≥3 late toxicities (p = 0.0072) and tumor volume > 25 cc (p = 0.032) predicted significantly worse overall PR-QOL. Oral cavity recurrence predicted significant decrements in chewing (p = 0.0006), swallowing (p = 0.0301), and taste PR-QOL (p = 0.02). Nasal recurrence predicted significant decrements in taste PR-QOL (p = 0.030). Grade ≥3 late dysphagia predicted significant decline in chewing (p = 0.039) and swallowing (p = 0.0004). Grade ≥3 late osteonecrosis predicted significant differences in pain PR-QOL (p = 0.0026). Conclusion: PR-QOL across several domains declines immediately after SBRT for previously-irradiated rHNC before returning to baseline levels at 1 year. Long-term PR-QOL declines thereafter. Patients with grade ≥3 late toxicities or tumor volume >25 cc report reduced long-term overall PR-QOL, likely representing late disease progression. Specific organ recurrence and grade ≥3 late toxicities predict decrements in specific PR-QOL domains.

Increasing use of positron emission tomography among medicare beneficiaries undergoing radical cystectomy.

OBJECTIVE: To examine factors associated with PET scan use in the pre-operative evaluation of patients diagnosed with bladder cancer. METHODS: Using SEER-Medicare data, we identified bladder cancer patients who underwent radical cystectomy from 2006 to 2011 (n = 4,138). The primary outcome was PET scan use within 6 months before surgery. To examine predictors of PET scan use, we fit a mixed logit model with health service area as a random effect to account for patients nested within health service areas. We also calculated the adjusted probability of use over time and examined variation among the highest volume surgeons. RESULTS: Among the 4,138 patients, 406 (10%) received a pre-operative PET scan. The adjusted probability of a patient undergoing a PET scan increased from 0.04 in 2004 to 0.10 in 2011 (p < .001). Among the 78 highest volume surgeons, there was significant variation in PET scan use (p < .001). Patients with non-urothelial histology, measurement of alkaline phosphatase levels, and receipt of neoadjuvant chemotherapy were more likely to receive PET scan (all p < .05). CONCLUSION: Use of PET prior to radical cystectomy doubled over a 5-year period, suggesting its increased use in patients with muscle-invasive bladder cancer, particularly those with high-risk disease. Whether its use is warranted and improves patient outcomes is not clear and requires further studies.

The Development and Validation of Prostate Cancer-specific Physician-Hospital Networks.

OBJECTIVE: To develop prostate cancer-specific physician-hospital networks to define hospital-based units that more accurately group hospitals, providers, and the patients they serve. METHODS: Using Surveillance, Epidemiology, and End Results-Medicare, we identified men diagnosed with localized prostate cancer between 2007 and 2011. We created physician-hospital networks by assigning each patient to a physician and each physician to a hospital based on treatment patterns. We assessed content validity by examining characteristics of hospitals anchoring the physician-hospital networks and of the patients associated with these hospitals. RESULTS: We identified 42,963 patients associated with 344 physician-hospital networks. Networks anchored by a teaching hospital (compared to a nonteaching hospital) had higher median numbers of prostate cancer patients (117 [interquartile range {71-189} vs 82 {50-126}]) and treating physicians (7 [4-11] vs 4 [3-6]) (both P <0.001). On average, patients traveled farther to networks anchored by a teaching hospital (49 miles [standard deviation] [207] vs 41 [183]; P <.001). Hospitals known as high-volume centers for robotic prostatectomies, proton-beam therapy, and active surveillance had network rates for these procedures well above the mean. Hospitals known as safety net providers served higher proportions of minorities. CONCLUSION: We empirically developed prostate-cancer specific physician-hospital networks that exhibit content validity and are relevant from a clinical and policy perspective. They have the potential to become targets for policy interventions focused on improving the delivery of prostate cancer care.

Which Dose Specification Should Be Used for NRG Radiation Therapy Trials: Dose-to-Medium or Dose-to-Water?

PURPOSE: To compare the doses calculated by the Analytical Anisotropic Algorithm (AAA), Acuros dose-to-medium, and Acuros dose-to-water for the patients with lung cancer treated at our institution and show that further investigation and clarification are needed about what dose specifications should be used for NRG clinical trials. METHODS AND MATERIALS: Twenty-one patients with lung cancer who previously received intensity modulated radiation therapy or volumetric modulated arc therapy-based treatments at our institution were analyzed by recalculating their plans for each one with the AAA algorithm (reviewed and approved by our radiation oncologists) and with both reporting modes of the Acuros algorithm. All plans used the same monitor units as the original approved plan and a 2.5-mm grid size. For each patient, D100 of clinical target volume (CTV) and CTV coverage ratios in each plan were compared, and dose distributions and dose-volume histograms calculated by AAA, Acuros dose-to-water (Dw,m), and Acuros dose-to-medium (Dm,m) were compared as well. RESULTS: Differences between CTV D100 calculated by AAA and Acuros Dm,m were larger than the differences between AAA and Acuros XB Dw,m for all patients. When D100 of CTV was evaluated, the largest difference between AAA and Acuros Dm,m was 14.12% and between AAA and Acuros XB Dw,m was 3.68%. The average differences between the CTV D100 calculated by AAA and Acuros Dm,m was 5.39%. Coverage ratio between Acuros Dm,m and AAA ranges from 51.08% to 100% with an average of 91.32%; coverage ratio between Acuros Dw,m and AAA ranges from 87.2% to 100.41% with average of 98.94%; coverage ratio between Acuros Dm,m and Acuros Dw,m ranges from 58.58% to 100% with an average of 92.03%. CONCLUSIONS: The present study shows large and systematic differences in doses calculated by AAA and Acuros Dm,m. Therefore, further investigation and clarification are needed about which dose reporting mode should be used.

A Multi-faceted Intervention Aimed at Black-White Disparities in the Treatment of Early Stage Cancers: The ACCURE Pragmatic Quality Improvement trial.

BACKGROUND: Reports continue to show that Blacks with curable lung or breast cancer complete treatment less often than similar Whites contributing to worse survival. ACCURE is an intervention trial designed to address this problem. PATIENTS AND METHODS: A pragmatic, quality improvement trial comparing an intervention group to retrospective and concurrent controls. Patients with early stage breast or lung cancer aged 18 to 85 were enrolled (N = 302) at 2 cancer centers between April 2013 and March 2015 for the intervention component. Data from patients seen between January 2007 and December 2012 with these diagnoses were obtained to establish control completion rates. Concurrent data for non-study patients were used to identify secular trends. The intervention included: a real time registry derived from electronic health records of participants to signal missed appointments or unmet care milestones, a navigator, and clinical feedback. The primary outcome was "Treatment Complete", a composite variable representing completion of surgery, recommended radiation and chemotherapy for each patient. RESULTS: The mean age in the intervention group was 63.1 years; 37.1% of patients were Black. Treatment completion in retrospective and concurrent controls showed significant Black-White differences (Blacks (B) 79.8% vs. Whites (W) 87.3%, p < 0.001; 83.1% B vs. 90.1% W, p < 0.001, respectively). The disparity lessened within the intervention (B 88.4% and W 89.5%, p = 0.77). Multivariate analyses confirmed disparities reduction. OR for Black-White disparity within the intervention was 0.98 (95% CI 0.46-2.1); Black completion in the intervention compared favorably to Whites in retrospective (OR 1.6; 95% CI 0.90-2.9) and concurrent (OR 1.1; 95% CI 0.59-2.0) controls. CONCLUSION: A real time registry combined with feedback and navigation improved completion of treatment for all breast and lung cancer patients and narrowed disparities. Similar multi-faceted interventions could mitigate disparities in the treatment of other cancers and chronic conditions.

Assessment of deep inspiration breath hold technique setup reproducibility using mega voltage imaging for left breast cancer radiation therapy-integrated network study.

We evaluated daily setup reproducibility of deep inspiration breath hold (DIBH) using mega voltage (MV) imaging for left breast cancer radiation therapy. Analysis of 109 left breast cancer patients across UPMC Hillman Cancer Center network treated using DIBH technique with daily MV imaging was done. Patient characteristics, MV imaging procedure used and inter-fraction directional shifts were collected. For the statistical analyses, we separated all patients into 2 groups in each of the following 3 categories; (1) obese (BMI ≥ 30) vs nonobese, (2) mastectomy vs lumpectomy, (3) internal mammary node (IMN) treatment vs no IMN treatment. The group mean inter-fraction directional shifts were as following: (1) 0.7 mm (superior), 0.8 mm (inferior); (2) 0.65 mm (left), 0.64 mm (right); (3) 0.89 mm (anterior), 0.83 mm (posterior). Also, any directional shift ≥ 2 mm, ≥ 3 mm, ≥ 4 mm, ≥ 5 mm, ≥ 10 mm was found to be 52.9%, 37.6%, 30.9%, 21.9%, 3.7% of total fractions, respectively. In the stratified analysis, obese patients had larger directional shifts (p < 0.05) and highly associated with number of fractions for ≥ 5 mm in any directional shift compared to nonobese patients (29% vs 17%; p = 0.04). DIBH setup for left breast cancer treatment at our large cancer center network was reproducible with any mean directional shifts less than 1.0 mm using MV imaging. Daily imaging would be more beneficial for obese patients compared to nonobese patients.

Patterns of stereotactic body radiation therapy: The influence of lung cancer treatment on prostate cancer treatment.

INTRODUCTION: Technology availability and prior experience with novel cancer treatments may partially drive their use. We sought to examine this issue in the context of stereotactic body radiation therapy (SBRT) by studying how its use for an established indication (lung cancer) impacts its use for an emerging indication (prostate cancer). METHODS: Using SEER-Medicare from 2007 to 2011, we developed prostate cancer-specific physician-hospital networks. Our primary dependent variable was SBRT use for prostate cancer and our primary independent variable was SBRT use for lung cancer, both at the network level. To assess the influence of SBRT availability and experiential use, we generated predicted probabilities of SBRT use for prostate cancer stratified by a network's use of lung cancer SBRT, adjusting for network characteristics. To assess intensity of use, we examined the correlation between the proportion of prostate cancer patients and lung cancer patients receiving SBRT within a network. RESULTS: We identified 316 networks that served 41,034 prostate cancer and 83,433 lung cancer patients. A network was significantly more likely to use SBRT for prostate cancer if that network used SBRT for lung cancer (e.g., in 2011, odds ratio [OR] 12.7; 95% confidence interval [CI] 3.9-41.8). The Pearson's correlation between the proportion of prostate cancer patients and lung cancer patients receiving SBRT in a network was 0.34, which was not statistically significant (P = 0.12). CONCLUSIONS: SBRT availability and experiential use for lung cancer influences its use for prostate cancer, but intensity of use for one does not relate to intensity of use for the other.

The Influence of Stereotactic Body Radiation Therapy Adoption on Prostate Cancer Treatment Patterns.

PURPOSE: To our knowledge it is unknown whether stereotactic body radiation therapy of prostate cancer is a substitute for other radiation treatments or surgery, or for expanding the pool of patients who undergo treatment instead of active surveillance. MATERIALS AND METHODS: Using SEER (Surveillance, Epidemiology, and End Results)-Medicare we identified men diagnosed with prostate cancer between 2007 and 2011. We developed physician-hospital networks by identifying the treating physician of each patient based on the primary treatment received and subsequently assigning each physician to a hospital. We examined the relative distribution of prostate cancer treatments stratified by whether stereotactic body radiation therapy was performed in a network by fitting logistic regression models with robust SEs to account for patient clustering in networks. RESULTS: We identified 344 physician-hospital networks, including 30 (8.7%) and 314 (91.3%) in which stereotactic body radiation therapy was and was not performed, respectively. Networks in which that therapy was and was not done did not differ with time in the performance of robotic and radical prostatectomy, and active surveillance (all p >0.05). The relationship with intensity modulated radiation therapy did not show any consistent temporal pattern. In networks in which it was performed less intensity modulated radiation therapy was initially done but there were similar rates in later years. Brachytherapy trends differed among networks in which stereotactic body radiation therapy was vs was not performed with a lower brachytherapy rate in networks in which stereotactic body radiation therapy was done (p=0.03). CONCLUSIONS: Surgery and active surveillance rates did not differ in networks in which stereotactic body radiation therapy was vs was not performed but when that therapy was done there was a lower brachytherapy rate. Stereotactic body radiation therapy may represent more of an alternative to brachytherapy than to active surveillance.

Early clinical experience with varian halcyon V2 linear accelerator: Dual-isocenter IMRT planning and delivery with portal dosimetry for gynecological cancer treatments.

PURPOSE: Varian Halcyon linear accelerator version 2 (The Halcyon 2.0) was recently released with new upgraded features. The aim of this study was to report our clinical experience with Halcyon 2.0 for a dual-isocenter intensity-modulated radiation therapy (IMRT) planning and delivery for gynecological cancer patients and examine the feasibility of in vivo portal dosimetry. METHODS: Twelve gynecological cancer patients were treated with extended-field IMRT technique using two isocenters on Halcyon 2.0 to treat pelvis and pelvic/or para-aortic nodes region. The prescription dose was 45 Gy in 25 fractions (fxs) with simultaneous integrated boost (SIB) dose of 55 or 57.5 Gy in 25 fxs to involved nodes. All treatment plans, pretreatment patient-specific QA and treatment delivery records including daily in vivo portal dosimetry were retrospectively reviewed. For in vivo daily portal dosimetry analysis, each fraction was compared to the reference baseline (1st fraction) using gamma analysis criteria of 4 %/4 mm with 90% of total pixels in the portal image planar dose. RESULTS: All 12 extended-field IMRT plans met the planning criteria and delivered as planned (a total of 300 fractions). Conformity Index (CI) for the primary target was achieved with the range of 0.99-1.14. For organs at risks, most were well within the dose volume criteria. Treatment delivery time was from 5.0 to 6.5 min. Interfractional in vivo dose variation exceeded gamma analysis threshold for 8 fractions out of total 300 (2.7%). These eight fractions were found to have a relatively large difference in small bowel filling and SSD change at the isocenter compared to the baseline. CONCLUSION: Halcyon 2.0 is effective to create complex extended-field IMRT plans using two isocenters with efficient delivery. Also Halcyon in vivo dosimetry is feasible for daily treatment monitoring for organ motion, internal or external anatomy, and body weight which could further lead to adaptive radiation therapy.