Design of a 3D patient-specific collision avoidance virtual framework for half-gantry proton therapy system.

INTRODUCTION: This study presents a comprehensive collision avoidance framework based on three-dimension (3D) computer-aided design (CAD) modeling, a graphical user interface (GUI) as peripheral to the radiation treatment planning (RTP) environment, and patient-specific plan parameters for intensity-modulated proton therapy (IMPT). METHODS: A stand-alone software application was developed leveraging the Varian scripting application programming interface (API) for RTP database object accessibility. The Collision Avoider software models the Hitachi ProBeat-V half gantry design and the Kuka robotic couch with triangle mesh structures. Patient-specific plan parameters are displayed in the collision avoidance software for potential proximity evaluation. The external surfaces of the patients and the immobilization devices are contoured based on computed tomography (CT) images. A "table junction-to-CT-origin" (JCT) measurement is made for every patient at the time of CT simulation to accurately provide reference location of the patient contours to the treatment couch. Collision evaluations were performed virtually with the program during treatment planning to prevent four major types of collisional events: collisions between the gantry head and the treatment couch, gantry head and the patient's body, gantry head and the robotic arm, and collisions between the gantry head and the immobilization devices. RESULTS: The Collision Avoider software was able to accurately model the proton treatment delivery system and the robotic couch position. Commonly employed clinical beam configuration and JCT values were investigated. Brain and head and neck patients require more complex gantry and patient positioning system configurations. Physical measurements were performed to validate 3D CAD model geometry. Twelve clinical proton treatment plans were used to validate the accuracy of the software. The software can predict all four types of collisional events in our clinic since its full implementation in 2020. CONCLUSION: A highly efficient patient-specific collision prevention program for scanning proton therapy has been successfully implemented. The graphical program has provided accurate collision detection since its inception at our institution.

Immediate tissue expander or implant-based breast reconstruction does not compromise the oncologic delivery of post-mastectomy radiotherapy (PMRT).

PURPOSE: Increasingly, women are choosing immediate breast reconstruction (IBR) following mastectomy. Reports have indicated IBR may compromise post-mastectomy radiotherapy (PMRT). We investigated the impact of IBR on timing of PMRT, target coverage, and doses to organs at risk in a modern radiotherapy practice using advanced planning techniques. METHODS: Between 2013 and 2015, PMRT was delivered to 116 patients (66 mastectomy alone, 50 IBR). PMRT was delivered with a median dose of 50 Gy in 25 fractions. Left-sided patients were treated in breath-hold under image guidance. Differences in dosimetric parameters and time to the initiation of PMRT were assessed between patients with and without reconstruction. RESULTS: Reconstructed patients were younger and had lower clinical stage disease. Reconstruction did not significantly increase the mean time to PMRT initiation (51 days reconstructed vs. 45 days non-reconstructed, p = 0.14) or the number of patients who initiated PMRT within 12 weeks of the last therapeutic intervention (48/50 [96.0] vs. 61/66 [92.4%], p = 0.41). There was no significant difference in the percentage of patients in whom the internal mammary lymph nodes (IMNs) were targeted (72 vs. 80%, p = 0.29) or in IMN target coverage (mean IMN V40.5 Gy 92.6 vs. 94.1%, p = 0.62). Reconstruction did not significantly affect the mean ipsilateral lung V20 (25.4 vs. 26.4%, p = 0.37) or the mean heart dose (2.2 vs. 2.1 Gy, p = 0.63). CONCLUSIONS: In a specialized breast multidisciplinary practice, immediate breast reconstruction did not significantly delay PMRT, compromise target coverage, or increase dose to organs at risk.

A Novel Treatment Schedule for Rapid Completion of Surgery and Radiation in Early-Stage Breast Cancer.

BACKGROUND: Data support the use of accelerated partial-breast irradiation (APBI) for early-stage breast cancer. We initiated a prospective protocol for intraoperative APBI catheter placement using a multi-lumen strut-based device. We hypothesized that with intraoperative pathology assessment of margins and sentinel nodes, all locoregional treatment (surgery and APBI) could be completed within 10 days with acceptable complication rates and cosmesis. METHODS: Eligible patients included women age 50 years or older with clinical T1 estrogen receptor positive (ER+) sentinel lymph node (SLN)-negative invasive ductal cancer or pure ductal carcinoma in situ. Patients were prospectively registered. Cosmesis was assessed using photographs graded independently by three investigators for patients with photos taken 6 months or longer after treatment. RESULTS: From October 2012 to August 2015, we enrolled 123 patients; 110 (90 %) underwent intraoperative catheter placement, whereas 13 did not due to intraoperative pathology findings. 109 APBI patients (99 %) completed their prescribed radiotherapy within 5 days, and all their locoregional therapy within 9 days, whereas one patient with a delayed positive SLN received only boost radiotherapy via catheter followed by conventional whole breast radiation. The 30-day complication rate was 6 %. In 81 patients with at least one-year followup, complications occurred in 14 (17 %) (including infection in five patients and symptomatic seroma in five patients) and correlated with device size (p = 0.05) but not with tumor size or location. The local recurrence rate was 1.8 % (two patients). Scored cosmesis was excellent or good in 88 % and fair in 12 % of patients. CONCLUSIONS: A protocol for intraoperative strut-based APBI catheter placement using careful patient selection and intraoperative pathology assessment can deliver efficient, effective treatment for early breast cancer.

Investigation of dosimetric effect of beam current fluctuations in synchrotron-based proton PBS continuous scanning.

Objective.In proton pencil beam scanning (PBS) continuous delivery, the beam is continuously delivered without interruptions between spots. For synchrotron-based systems, the extracted beam current exhibits a spill structure, and recent publications on beam current measurements have demonstrated significant fluctuations around the nominal values. These fluctuations potentially lead to dose deviations from those calculated assuming a stable beam current. This study investigated the dosimetric implications of such beam current fluctuations during proton PBS continuous scanning.Approach.Using representative clinical proton PBS plans, we performed simulations to mimic a worst-case clinical delivery environment with beam current varies from 50% to 250% of the nominal values. The simulations used the beam delivery parameters optimized for the best beam delivery efficiency of the upcoming particle therapy system at Mayo Clinic Florida. We reconstructed the simulated delivered dose distributions and evaluated the dosimetric impact of beam current fluctuations.Main results.Despite significant beam current fluctuations resulting in deviations at each spot level, the overall dose distributions were nearly identical to those assuming a stable beam current. The 1 mm/1% Gamma passing rate was 100% for all plans. Less than 0.2% root mean square error was observed in the planning target volume dose-volume histogram. Minimal differences were observed in all dosimetric evaluation metrics.Significance.Our findings demonstrate that with our beam delivery system and clinical planning practice, while significant beam current fluctuations may result in large local move monitor unit deviations at each spot level, the overall impact on the dose distribution is minimal.

Stereotactic body proton therapy for early stage non-small cell lung cancer - Technical challenges and solutions: The MD Anderson experience.

Our randomized clinical study comparing stereotactic body radiotherapy (SBRT) and stereotactic body proton therapy (SBPT) for early stage non-small cell lung cancer (NSCLC) was closed prematurely owing to poor enrollment, largely because of lack of volumetric imaging and difficulty in obtaining insurance coverage for the SBPT group. In this article, we describe technology improvements in our new proton therapy center, particularly in image guidance with cone beam CT (CBCT) and CT on rail (CTOR), as well as motion management with real-time gated proton therapy (RGPT) and optical surface imaging. In addition, we have a treatment planning system that provides better treatment plan optimization and more accurate dose calculation. We expect to re-start the SBPT program, including for early stage NSCLC as well as for other disease sites soon after starting patient treatment at our new proton therapy center.

Detection of Early Myocardial Dysfunction by Imaging Biomarkers in Cancer Patients Undergoing Photon Beam vs. Proton Beam Radiotherapy: A Prospective Study.

1. Background: We sought to determine acute and subacute changes in cardiac function after proton beam (PBT) and photon beam (PhT) radiotherapy (RT) using conventional and two-dimensional speckle tracking echocardiography (2D-STE) in patients with malignant breast and thoracic tumors. 2. Methods: Between March 2016 and March 2017, 70 patients with breast or thoracic cancer were prospectively enrolled and underwent transthoracic echocardiography with comprehensive strain analysis at pretreatment, mid-treatment, end of treatment, and 3 months after RT. 3. Results: PBT was used to treat 44 patients; PhT 26 patients. Mean ± SD age was 55 ± 12 years; most patients (93%) were women. The median (interquartile range) of the mean heart dose was lower in the PBT than the PhT group (47 [27-79] vs. 217 [120-596] cGy, respectively; p < 0.001). Ejection fraction did not change in either group. Only the PhT group had reduced systolic tissue Doppler velocities at 3 months. 2D-STE showed changes in endocardial and epicardial longitudinal, radial, and circumferential early diastolic strain rate (SRe) in patients undergoing PhT (global longitudinal SRe, pretreatment vs. end of treatment (p = 0.04); global circumferential SRe, pretreatment vs. at 3-month follow-up (p = 0.003); global radial SRe, pretreatment vs. at 3-month follow-up (p = 0.02) for endocardial values). Epicardial strain values decreased significantly only in patients treated with PhT. Patients in the PhT group had a significant decrease in epicardial global longitudinal systolic strain rate (GLSRs) (epicardial GLSRs, at baseline vs. at end of treatment [p = 0.009]) and in GCSRe and GRSRe (epicardial GCSRe, at baseline vs. at 3-month follow-up (p = 0.02); epicardial GRSRe, at baseline vs. at 3-month follow-up (p = 0.03)) during treatment and follow-up. No changes on 2D-STE were detected in the PBT group. 4. Conclusions: Patients who underwent PhT but not PBT had reduced tissue Doppler velocities and SRe values during follow-up, suggesting early myocardial relaxation abnormalities. PBT shows promise as a cardiac-sparing RT technology.

Deep learning-based dose prediction to improve the plan quality of volumetric modulated arc therapy for gynecologic cancers.

BACKGROUND: In recent years, deep-learning models have been used to predict entire three-dimensional dose distributions. However, the usability of dose predictions to improve plan quality should be further investigated. PURPOSE: To develop a deep-learning model to predict high-quality dose distributions for volumetric modulated arc therapy (VMAT) plans for patients with gynecologic cancer and to evaluate their usability in driving plan quality improvements. METHODS: A total of 79 VMAT plans for the female pelvis were used to train (47 plans), validate (16 plans), and test (16 plans) 3D dense dilated U-Net models to predict 3D dose distributions. The models received the normalized CT scan, dose prescription, and target and normal tissue contours as inputs. Three models were used to predict the dose distributions for plans in the test set. A radiation oncologist specializing in the treatment of gynecologic cancers scored the test set predictions using a 5-point scale (5, acceptable as-is; 4, prefer minor edits; 3, minor edits needed; 2, major edits needed; and 1, unacceptable). The clinical plans for which the dose predictions indicated that improvements could be made were reoptimized with constraints extracted from the predictions. RESULTS: The predicted dose distributions in the test set were of comparable quality to the clinical plans. The mean voxel-wise dose difference was -0.14 ± 0.46 Gy. The percentage dose differences in the predicted target metrics of D 1 % ${D}_{1{\mathrm{\% }}}$ and D 98 % ${D}_{98{\mathrm{\% }}}$ were -1.05% ± 0.59% and 0.21% ± 0.28%, respectively. The dose differences in the predicted organ at risk mean and maximum doses were -0.30 ± 1.66 Gy and -0.42 ± 2.07 Gy, respectively. A radiation oncologist deemed all of the predicted dose distributions clinically acceptable; 12 received a score of 5, and four received a score of 4. Replanning of flagged plans (five plans) showed that the original plans could be further optimized to give dose distributions close to the predicted dose distributions. CONCLUSIONS: Deep-learning dose prediction can be used to predict high-quality and clinically acceptable dose distributions for VMAT female pelvis plans, which can then be used to identify plans that can be improved with additional optimization.

Automated contouring and statistical process control for plan quality in a breast clinical trial.

Background and purpose: Automatic review of breast plan quality for clinical trials is time-consuming and has some unique challenges due to the lack of target contours for some planning techniques. We propose using an auto-contouring model and statistical process control to independently assess planning consistency in retrospective data from a breast radiotherapy clinical trial. Materials and methods: A deep learning auto-contouring model was created and tested quantitatively and qualitatively on 104 post-lumpectomy patients' computed tomography images (nnUNet; train/test: 80/20). The auto-contouring model was then applied to 127 patients enrolled in a clinical trial. Statistical process control was used to assess the consistency of the mean dose to auto-contours between plans and treatment modalities by setting control limits within three standard deviations of the data's mean. Two physicians reviewed plans outside the limits for possible planning inconsistencies. Results: Mean Dice similarity coefficients comparing manual and auto-contours was above 0.7 for breast clinical target volume, supraclavicular and internal mammary nodes. Two radiation oncologists scored 95% of contours as clinically acceptable. The mean dose in the clinical trial plans was more variable for lymph node auto-contours than for breast, with a narrower distribution for volumetric modulated arc therapy than for 3D conformal treatment, requiring distinct control limits. Five plans (5%) were flagged and reviewed by physicians: one required editing, two had clinically acceptable variations in planning, and two had poor auto-contouring. Conclusions: An automated contouring model in a statistical process control framework was appropriate for assessing planning consistency in a breast radiotherapy clinical trial.

Deep Learning-Based Dose Prediction for Automated, Individualized Quality Assurance of Head and Neck Radiation Therapy Plans.

PURPOSE: This study aimed to use deep learning-based dose prediction to assess head and neck (HN) plan quality and identify suboptimal plans. METHODS AND MATERIALS: A total of 245 volumetric modulated arc therapy HN plans were created using RapidPlan knowledge-based planning (KBP). A subset of 112 high-quality plans was selected under the supervision of an HN radiation oncologist. We trained a 3D Dense Dilated U-Net architecture to predict 3-dimensional dose distributions using 3-fold cross-validation on 90 plans. Model inputs included computed tomography images, target prescriptions, and contours for targets and organs at risk (OARs). The model's performance was assessed on the remaining 22 test plans. We then tested the application of the dose prediction model for automated review of plan quality. Dose distributions were predicted on 14 clinical plans. The predicted versus clinical OAR dose metrics were compared to flag OARs with suboptimal normal tissue sparing using a 2 Gy dose difference or 3% dose-volume threshold. OAR flags were compared with manual flags by 3 HN radiation oncologists. RESULTS: The predicted dose distributions were of comparable quality to the KBP plans. The differences between the predicted and KBP-planned D1%,D95%, and D99% across the targets were within -2.53% ± 1.34%, -0.42% ± 1.27%, and -0.12% ± 1.97%, respectively, and the OAR mean and maximum doses were within -0.33 ± 1.40 Gy and -0.96 ± 2.08 Gy, respectively. For the plan quality assessment study, radiation oncologists flagged 47 OARs for possible plan improvement. There was high interphysician variability; 83% of physician-flagged OARs were flagged by only one of 3 physicians. The comparative dose prediction model flagged 63 OARs, including 30 of 47 physician-flagged OARs. CONCLUSIONS: Deep learning can predict high-quality dose distributions, which can be used as comparative dose distributions for automated, individualized assessment of HN plan quality.

High Positive Predictive Value of Multitarget Stool DNA After Aerodigestive Tract Radiotherapy.

BACKGROUND AND AIMS: Multitarget stool DNA (mt-sDNA) is approved for average-risk colorectal cancer screening; test performance in persons with prior radiation therapy (RT) has not been studied. RT can induce gastrointestinal bleeding and alter DNA methylation, which may affect mt-sDNA accuracy. Among patients previously treated with RT, we aimed to measure the positive predictive value (PPV) of mt-sDNA and compare these results to historical estimates of mt-sDNA PPV among average-risk patients. METHODS: After institutional review board approval, we conducted a retrospective cohort study of a multisite academic and community-based practice. Patients with RT and subsequent mt-sDNA use during the study period (2014-2016) were identified. The findings at diagnostic colonoscopy were compared with published reports among average-risk patients. Nominal P values were generated by 2-tailed Fisher's exact testing in comparisons of colorectal neoplasia (CRN) rates between groups. RESULTS: There were 220 patients who had RT before mt-sDNA testing. RT was delivered along the aerodigestive tract in 108 patients. Mt-sDNA tests were positive in 45 of 220 patients (20%), and colonoscopy findings were available for 42; 31 of 42 patients (74%) had CRN. PPV by mt-sDNA was similar when stratified by site of prior RT (along vs outside the aerodigestive tract; P = 1.00). Detection of advanced CRN (36%) was nominally higher than previously published retrospective (27%) and prospective (20%) studies. The median time from the start of RT to mt-sDNA use was 7 (interquartile range, 3-14) years. CONCLUSION: With a test positivity rate and PPV for CRN similar to reports among average-risk patients, prior RT does not appear to adversely affect mt-sDNA performance.

Technical Delivery Parameters of 2000 Proton Treatment Courses.

PURPOSE: To summarize the technical delivery parameters of proton plans delivered at the Mayo Clinic in Rochester, Minnesota. MATERIALS AND METHODS: The database of treated patient proton plans was queried to extract field parameters such as gantry angle, patient support angle, minimum and maximum water-equivalent depth (WED) treated, number of layers, field size, patient orientation, and monitor units. The plans were analyzed in aggregate, by disease site, and by fractionation. RESULTS: There were 2963 proton plans for 2023 distinct treatment sites delivered between June 2015 and September 2018. The mean number of fields per plan was 2.8. The mean number of energy layers per field was 51.9. The mean monitor unit per field was 117.4. The median maximum field dimension was 12.4 cm; 95% of the fields had a maximum dimension < 28.7 cm, and the maximum field dimension was 39.8 cm. The median maximum field WED was 16.4 cm; 95% of the fields reached a maximum WED of ≤ 26.4 cm, and the maximum field WED was 32.4 cm. CONCLUSION: A large variety of disease sites were treated using the maximum field size (40 cm) and WED (32.4 cm) capabilities of our half-gantry system.

Comparing bowel and urinary domains of patient-reported quality of life at the end of and 3 months post radiotherapy between intensity-modulated radiotherapy and proton beam therapy for clinically localized prostate cancer.

PURPOSE: To prospectively assess acute differences in patient-reported outcomes in bowel and urinary domains between intensity-modulated radiotherapy (IMRT) and proton beam therapy (PBT) for prostate cancer. METHODS AND MATERIALS: Bowel function (BF), urinary irritative/obstructive symptoms (UO), and urinary incontinence (UI) domains of EPIC-26 were collected in patients with T1-T2 prostate cancer receiving IMRT or PBT at a tertiary cancer center (2015-2018). Mean changes in domain scores were analyzed from pretreatment to the end of and 3 months post-radiotherapy for each modality. A clinically meaningful change was defined as a score change >50% of the baseline standard deviation. RESULTS: A total of 157 patients receiving IMRT and 105 receiving PBT were included. There were no baseline differences in domain scores between cohorts. At the end of radiotherapy, there was significant and clinically meaningful worsening of BF and UO scores for patients receiving either modality. In the BF domain, the IMRT cohort experienced greater decrement (-13.0 vs -6.7, P < .01), and had a higher proportion of patients with clinically meaningful reduction (58.4% vs 39.5%, P = .01), compared to PBT. At 3 months post-radiotherapy, the IMRT group had significant and clinically meaningful worsening of BF (-9.3, P < .001), whereas the change in BF score of the PBT cohort was no longer significant or clinically meaningful (-1.2, P = .25). There were no significant or clinically meaningful changes in UO or UI 3 months post-radiotherapy. CONCLUSIONS: PBT had less acute decrement in BF than IMRT following radiotherapy. There was no difference between the two modalities in UO and UI.

Reducing Heart Dose with Protons and Cardiac Substructure Sparing for Mediastinal Lymphoma Treatment.

PURPOSE: Electrocardiogram-gated computed tomography with coronary angiography can be used for cardiac substructure sparing (CSS) optimization, which identifies and improves avoidance of cardiac substructures when treating with intensity modulated radiotherapy (IMRT). We investigated whether intensity modulated proton therapy (IMPT) would further reduce dose to cardiac substructures for patients with mediastinal lymphoma. PATIENTS AND METHODS: Twenty-one patients with mediastinal lymphoma were enrolled and underwent electrocardiogram-gated computed tomography angiography during or shortly after simulation for radiotherapy planning. Thirteen patients with delineated cardiac substructures underwent comparative planning with both IMPT and IMRT. Plans were normalized for equivalent (95%) target volume coverage for treatment comparison. RESULTS: Thirteen patients met criteria for this study. The median size of the mediastinal lymphadenopathy was 7.9 cm at the greatest diameter. Compared with IMRT-CSS, IMPT-CSS significantly reduced mean dose to all cardiac substructures, including 3 coronary arteries and 4 cardiac valves. Use of IMPT significantly reduced average whole-heart dose from 9.6 to 4.9 Gy (P < .0001), and average mean lung dose was 9.7 vs 5.8 Gy (P < .0001). Prospectively defined clinically meaningful improvement was observed in at least 1 coronary artery in 9 patients (69%), at least 1 cardiac valve in 10 patients (77%), and whole heart in all 13 patients. CONCLUSIONS: For patients with mediastinal lymphoma, IMPT-CSS treatment planning significantly reduced radiation dose to cardiac substructures. The significant improvements outlined in this study for proton therapy suggest possible clinical improvement in alignment with previous analyses of CSS optimization.

Incorporation of Biologic Response Variance Modeling Into the Clinic: Limiting Risk of Brachial Plexopathy and Other Late Effects of Breast Cancer Proton Beam Therapy.

PURPOSE: The relative biologic effectiveness (RBE) rises with increasing linear energy transfer toward the end of proton tracks. Presently, there is no consensus on how RBE heterogeneity should be accounted for in breast cancer proton therapy treatment planning. Our purpose was to determine the dosimetric consequences of incorporating a brachial plexus (BP) biologic dose constraint and to describe other clinical implications of biologic planning. METHODS AND MATERIALS: We instituted a biologic dose constraint for the BP in the context of MC1631, a randomized trial of conventional versus hypofractionated postmastectomy intensity modulated proton therapy (IMPT). IMPT plans of 13 patients treated before the implementation of the biologic dose constraint (cohort A) were compared with IMPT plans of 38 patients treated on MC1631 after its implementation (cohort B) using (1) a commercially available Eclipse treatment planning system (RBE = 1.1); (2) an in-house graphic processor unit-based Monte Carlo physical dose simulation (RBE = 1.1); and (3) an in-house Monte Carlo biologic dose (MCBD) simulation that assumes a linear relationship between RBE and dose-averaged linear energy transfer (product of RBE and physical dose = biologic dose). RESULTS: Before implementation of a BP biologic dose constraint, the Eclipse mean BP D0.01 cm3 was 107%, and the MCBD estimate was 128% (ie, 64 Gy [RBE = biologic dose] in 25 fractions for a 50-Gy [RBE = 1.1] prescription), compared with 100.0% and 116.0%, respectively, after the implementation of the constraint. Implementation of the BP biologic dose constraint did not significantly affect clinical target volume coverage. MCBD plans predicted greater internal mammary node coverage and higher heart dose than Eclipse plans. CONCLUSIONS: Institution of a BP biologic dose constraint may reduce brachial plexopathy risk without compromising target coverage. MCBD plan evaluation provides valuable information to physicians that may assist in making clinical judgments regarding relative priority of target coverage versus normal tissue sparing.

Association of tumor genomic factors and efficacy for metastasis-directed stereotactic body radiotherapy for oligometastatic colorectal cancer.

PURPOSE/OBJECTIVE(S): To report tumor genomic factors associated with overall survival (OS) and local failure (LF) for patients with colorectal cancer (CRC) who received metastasis-directed stereotactic body radiation therapy (SBRT). MATERIALS/METHODS: This was a retrospective review of patients with CRC who received metastasis-directed SBRT. Tumor genomic alterations were identified through KRAS, BRAF, or a 50-gene next generation sequencing panel. OS and LF were estimated using Kaplan-Meier and competing-risk methods. RESULTS: Eighty-five patients and 109 lesions were treated between 2008 and 2018. The median patient follow-up was 50 months (IQR: 28-107). The median and 5-year OS was 34 months and 26% (95% CI: 16-41%), respectively. The 2-year cumulative incidence of LF was 30% (95% CI: 23-41%). Univariate associates with OS included patient age ≥60 years, bone metastasis, increasing tumor size, KRAS mutation, and combined KRAS and TP53 mutation, while increasing tumor size, bone metastasis, biologically effective dose <100 Gy, and combined KRAS and TP53 mutation were associated with LF. Multivariate associates with OS included patient age ≥60 years (HR: 2.4, 95% CI: 1.2-4.8, p = 0.01), lesion size per 1 cm (HR: 1.3, 95% CI: 1.1-1.5, p < 0.01), and KRAS mutation (HR: 2.2, 95% CI: 1.2-4.3, p < 0.01), while no multivariable model for LF retained more than a single variable. CONCLUSION: Genomic factors, in particular KRAS and TP53 mutation, may assist in patient selection and radiotherapeutic decision-making for patients with oligometastatic CRC. Prospective validation, ideally with genomic correlation of all irradiated metastases, is warranted.

Comparative analysis of acute toxicities and patient reported outcomes between intensity-modulated proton therapy (IMPT) and volumetric modulated arc therapy (VMAT) for the treatment of oropharyngeal cancer.

BACKGROUND AND PURPOSE: IMPT improves normal tissue sparing compared to VMAT in treating oropharyngeal cancer (OPC). Our aim was to assess if this translates into clinical benefits. MATERIALS AND METHODS: OPC patients treated with definitive or adjuvant IMPT or VMAT from 2013 to 2018 were included. All underwent prospective assessment using patient-reported-outcomes (PROs) (EORTC-QLQ-H&N35) and provider-assessed toxicities (CTCAEv4.03). End-of-treatment and pretreatment scores were compared. PEG-tube use, hospitalization, and narcotic use were retrospectively collected. Statistical analysis used the Wilcoxon Rank-Sum Test with propensity matching for PROs/provider-assessed toxicities, and t-tests for other clinical outcomes. RESULTS: 46 IMPT and 259 VMAT patients were included; median follow-up was 12 months (IMPT) and 30 months (VMAT). Baseline characteristics were balanced except for age (p = 0.04, IMPT were older) and smoking (p < 0.01, 10.9% IMPT >20PYs, 29.3% VMAT). IMPT was associated with lower PEG placement (OR = 0.27; 95% CI: 0.12-0.59; p = 0.001) and less hospitalization ≤60 days post-RT (OR = 0.21; 95% CI:0.07-0.6, p < 0.001), with subgroup analysis revealing strongest benefits in patients treated definitively or with concomitant chemoradiotherapy (CRT). IMPT was associated with a relative risk reduction of 22.3% for end-of-treatment narcotic use. Patients reported reduced cough and dysgeusia with IMPT (p < 0.05); patients treated definitively or with CRT also reported feeling less ill, reduced feeding tube use, and better swallow. Provider-assessed toxicities demonstrated less pain and mucositis with IMPT, but more mucosal infection. CONCLUSION: IMPT is associated with improved PROs, reduced PEG-tube placement, hospitalization, and narcotic requirements. Mucositis, dysphagia, and pain were decreased with IMPT. Benefits were predominantly seen in patients treated definitively or with CRT.

Electrocardiogram-Gated Computed Tomography with Coronary Angiography for Cardiac Substructure Delineation and Sparing in Patients with Mediastinal Lymphomas Treated with Radiation Therapy.

PURPOSE: (1) Demonstrate feasibility of electrocardiogram-gated computed tomography with coronary angiography (E-CTA) in treatment planning for mediastinal lymphoma and (2) assess whether inclusion of cardiac substructures in the radiation plan optimization (CSS optimization) results in increased cardiac substructure sparing. METHODS AND MATERIALS: Patients with mediastinal lymphomas requiring radiation therapy were prospectively enrolled in an observational study. Patients completed a treatment planning computed tomography scan and E-CTA in the deep inspiration breath hold position. Avoidance structures (eg, coronary arteries and cardiac valves) were created in systole and diastole and then merged into a single planning organ-at-risk volume based on a cardiac substructure contouring atlas. In the photon cohort, 2 volumetric modulated arc therapy plans were created per patient with and without CSS optimization. Dosimetric endpoints were compared. RESULTS: In the photon cohort, 7 patients were enrolled. For all 7 patients, the treating physician elected to use the CSS optimization plan. At the individual level, 2 patients had reductions of 10.8% and 16.2% of the right coronary artery receiving at least 15 Gy, and 1 had a reduction of 9.6% of the left anterior descending artery receiving 30 Gy. No other differences for coronary arteries were detected between 15 and 30 Gy. Conversely, 5 of 7 patients had >10% reductions in dose between 15 to 30 Gy to at least 1 cardiac valve. The greatest reduction was 22.8% of the aortic valve receiving at least 30 Gy for 1 patient. At the cohort level, the maximum, mean, and 5-Gy increment analyses were nominally similar between planning techniques for all cardiac substructures and the lungs. CONCLUSIONS: Cardiac substructure delineation using E-CTA was feasible, and inclusion in optimization led to modest improvements in sparing of radiosensitive cardiac substructures for some patients.

IMPT versus VMAT for Pelvic Nodal Irradiation in Prostate Cancer: A Dosimetric Comparison.

PURPOSE: To compare dosimetric data of the organs at risk (OARs) and clinical target volumes (CTVs) between intensity-modulated proton therapy (IMPT) and volumetric-modulated arc therapy (VMAT) for patients undergoing prostate and elective, pelvic lymph node radiotherapy in the setting of unfavorable, intermediate and high-risk prostate carcinoma. METHODS AND MATERIALS: A study of moderately hypofractionated proton therapy (6750 centigray [cGy] in 25 fractions) is in progress for unfavorable, intermediate and high-risk prostate cancer where treatment includes an elective pelvic nodal CTV (4500 cGy in 25 fractions). Ten consecutively accrued patients were the subjects for dose-volume histogram comparison between IMPT and VMAT. Two treatment plans (IMPT and VMAT) were prepared for each patient with predefined planning objectives for target volumes and OARs. The IMPT plans were prepared with 2 lateral beams and VMAT plans with 2 arcs. RESULTS: The CTV coverage was adequate for both plans with 99% of CTVs receiving ≥ 100% of the prescription doses. Mean doses to the bladder, rectum, large bowel, and small bowel were lower with IMPT versus VMAT. Mean femoral head dose was greater with IMPT. The percentage of volumes of rectum receiving ≤ 47.5 Gy, large bowel receiving ≤ 27.5 Gy, small bowel receiving ≤ 30 Gy, and bladder receiving ≤ 37.5 Gy was less with IMPT versus VMAT, largely because of reduction in the low-dose "bath" associated with VMAT. CONCLUSIONS: In the setting of prostate and elective, pelvic nodal radiotherapy for prostate cancer, IMPT can significantly reduce the dose to OARs, in comparison to VMAT, and provide adequate target coverage.

3 fraction pencil-beam scanning proton accelerated partial breast irradiation: early provider and patient reported outcomes of a novel regimen.

BACKGROUND AND PURPOSE: To report dosimetry and early adverse effects, aesthetic, and patient-reported outcomes of a prospective study of 3-fraction pencil-beam scanning (PBS) proton accelerated partial irradiation (APBI). MATERIALS AND METHODS: Eligibility included women age ≥ 50 years with estrogen receptor positive (ER+), sentinel lymph node negative invasive or in-situ breast cancer measuring ≤2.5 cm. The prescription was 21.9 Gy (RBE 1.1) in 3 daily fractions to the post-operative tumor bed with a 1 cm expansion. Toxicities were collected using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0, 10-point Linear Analog Scale Assessment, Patient-Reported Outcomes Version of the CTCAE, and the Harvard Breast Cosmesis Scale. RESULTS: Seventy-six women were treated between 2015 and 2017. The median breast volume receiving 50% of prescription or more was 28%. Median mean heart, mean ipsilateral lung, and maximum skin dose were 0 Gy, 0.1 Gy, and 20.6 Gy, respectively. With a median follow-up of 12 months, no treatment-related toxicity grade ≥ 2 has been observed. Most common grade 1 adverse events were dermatitis (68%) and skin hyperpigmentation (18%). At 12 months, the only persistent toxicities were one patient with grade 1 breast edema and one patient with a grade 1 seroma. 90% of patients reported quality of life as ≥7 out of 10 (0 indicating "as bad as it can be" and 10 indicating "as good as it can be") and 98% of patients reported excellent or good cosmesis. CONCLUSION: 3-fraction PBS proton APBI is well tolerated with low rates of physician and patient reported early adverse effects. Follow-up is ongoing to assess late toxicities and disease control outcomes. Further investigation of this novel adjuvant treatment strategy is warranted.