Race and Ethnicity Representation in Phase 2/3 Oncology Clinical Trial Publications: A Systematic Review.

Importance: The five 1997 Office of Management and Budget races in the US include American Indian or Alaska Native, Asian, Black or African American, Native Hawaiian or Other Pacific Islander, and White, with Hispanic ethnicity. Despite the Affordable Care Act mandating Office of Management and Budget-based collecting and reporting standards, race and ethnicity publishing in medical journals is inconsistent, despite being necessary to achieve health equity. Objective: To quantify race and ethnicity reporting rates and calculate representation quotients (RQs) in published oncology clinical trials. Evidence Review: In this systematic review, PubMed and Embase were queried for phase 2/3 clinical trials of the 6 most common noncutaneous solid cancers, published between January 1, 2012, and December 31, 2022, in 4 high-impact journals. Trial characteristics were recorded. The RQs for each race and ethnicity were calculated by dividing the percent of representation in each clinical trial publication by the percent of year-matched, site-specific incident cancers in the US, compared with Kruskal-Wallis tests with Bonferroni correction (BC). Reporting was compared between journal publications and ClinicalTrials.gov. Findings: Among 1202 publications evaluated, 364 met inclusion criteria: 16 JAMA, 241 Journal of Clinical Oncology, 19 Lancet, and 88 New England Journal of Medicine. Publications included 268 209 patients (171 132 women [64%]), with a median of 356 (IQR, 131-800) patients per publication. Reported race and ethnicity included American Indian or Alaska Native in 52 (14%) publications, Asian in 196 (54%), Black or African American in 215 (59%), Hispanic in 67 (18%), Native Hawaiian or Other Pacific Islander in 28 (8%), and White in 254 (70%). Median RQ varied across race (P < .001 BC), with 1.04 (IQR, 0.09-4.77) for Asian, 0.98 (IQR, 0.86-1.06) for White, 0.42 (IQR, 0.12-0.75) for Black or African American, and 0.00 (IQR, 0.00-0.00) for both American Indian or Alaska Native and Native Hawaiian or Other Pacific Islander patients. Sensitivity analyses showed similar findings on subset analysis for US-only clinical trials. There was significantly less race and ethnicity reporting in the clinical trial publications compared with ClinicalTrials.gov documentation for American Indian or Alaska Native (14% vs 45%; P < .001 per McNemar χ2 test with continuity correction [MC]) and Native Hawaiian or Other Pacific Islander (8% vs 43%; P < .001 MC). Conclusions and Relevance: While most phase 2/3 oncology clinical trials published in high-impact journals report race and ethnicity, most did not report American Indian or Alaska Native and Native Hawaiian or Other Pacific Islander racial categories. Our findings support a call to action for consistent journal policies and transparent race and ethnicity reporting, in alignment with Affordable Care Act-concordant race and ethnicity federal reporting requirements.

Prospective phase II trial of preoperative hypofractionated proton therapy for extremity and truncal soft tissue sarcoma: the PRONTO study rationale and design.

BACKGROUND: Oncologic surgical resection is the standard of care for extremity and truncal soft tissue sarcoma (STS), often accompanied by the addition of pre- or postoperative radiation therapy (RT). Preoperative RT may decrease the risk of joint stiffness and fibrosis at the cost of higher rates of wound complications. Hypofractionated, preoperative RT has been shown to provide acceptable outcomes in prospective trials. Proton beam therapy (PBT) provides the means to decrease dose to surrounding organs at risk, such as the skin, bone, soft tissues, and adjacent joint(s), and has not yet been studied in patients with extremity and truncal sarcoma. METHODS: Our study titled "PROspective phase II trial of preoperative hypofractionated protoN therapy for extremity and Truncal soft tissue sarcOma (PRONTO)" is a non-randomized, prospective phase II trial evaluating the safety and efficacy of preoperative, hypofractionated PBT for patients with STS of the extremity and trunk planned for surgical resection. Adult patients with Eastern Cooperative Group Performance Status ≤ 2 with resectable extremity and truncal STS will be included, with the aim to accrue 40 patients. Treatment will consist of 30 Gy radiobiological equivalent of PBT in 5 fractions delivered every other day, followed by surgical resection 2-12 weeks later. The primary outcome is rate of major wound complications as defined according to the National Cancer Institute of Canada Sarcoma2 (NCIC-SR2) Multicenter Trial. Secondary objectives include rate of late grade ≥ 2 toxicity, local recurrence-free survival and distant metastasis-free survival at 1- and 2-years, functional outcomes, quality of life, and pathologic response. DISCUSSION: PRONTO represents the first trial evaluating the use of hypofractionated PBT for STS. We aim to prove the safety and efficacy of this approach and to compare our results to historical outcomes established by previous trials. Given the low number of proton centers and limited availability, the short course of PBT may provide the opportunity to treat patients who would otherwise be limited when treating with daily RT over several weeks. We hope that this trial will lead to increased referral patterns, offer benefits towards patient convenience and clinic workflow efficiency, and provide evidence supporting the use of PBT in this setting. TRIAL REGISTRATION: NCT05917301 (registered 23/6/2023).

Real-Time Gated Proton Therapy: Commissioning and Clinical Workflow for the Hitachi System.

Purpose: To describe the commissioning of real-time gated proton therapy (RGPT) and the establishment of an appropriate clinical workflow for the treatment of patients. Materials and Methods: Hitachi PROBEAT provides pencil beam scanning proton therapy with an advanced onboard imaging system including real-time fluoroscopy. RGPT utilizes a matching score to provide instantaneous system performance feedback and quality control for patient safety. The CIRS Dynamic System combined with a Thorax Phantom or plastic water was utilized to mimic target motion. The OCTAVIUS was utilized to measure end-to-end dosimetric accuracy for a moving target across a range of simulated situations. Using this dosimetric data, the gating threshold was carefully evaluated and selected based on the intended treatment sites and planning techniques. An image-guidance workflow was developed and applied to patient treatment. Results: Dosimetric data demonstrated that proton plan delivery uncertainty could be within 2 mm for a moving target. The dose delivery to a moving target could pass 3%/3 mm gamma analysis following the commissioning process and application of the clinical workflow detailed in this manuscript. A clinical workflow was established and successfully applied to patient treatment utilizing RGPT. Prostate cancer patients with implanted platinum fiducial markers were treated with RGPT. Their target motion and gating signal data were available for intrafraction motion analysis. Conclusion: Real-time gated proton therapy with the Hitachi System has been fully investigated and commissioned for clinical application. RGPT can provide advanced and reliable real-time image guidance to enhance patient safety and inform important treatment planning parameters, such as planning target volume margins and uncertainty parameters for robust plan optimization. RGPT improved the treatment of patients with prostate cancer in situations where intrafraction motion is more than defined tolerance.

Pilot Study Assessing Student Interest in Combined Residency Training Pathways With Radiation Oncology.

Purpose: Most medical students have limited exposure to radiation oncology (RO) before deciding which specialty to choose for residency. This may limit the number and diversity of RO applicants. The purpose of this study was to determine students' views on a combined pathway program of RO with internal medicine (IM), as well as other related medical specialties, as a potential means of overcoming barriers to interest in RO and the early decision point to solo training in a highly specialized field. Methods and Materials: In July to August 2022, all 299 United States student and postgraduate year 1 members of the American Society for Radiation Oncology were sent an electronic survey assessing their views on advantages and disadvantages of a combined IM/RO training pathway, and interest in several options of combined pathway programs. Results: Eighty participants completed the survey (response rate 27%). Thirty-four (43%) were very or extremely interested in IM/RO residency (median Likert-type rating 3, IQR 2-4). The most important potential advantages of an IM/RO pathway included greater flexibility in employment options (n = 51, 64%), enhanced general medical knowledge to facilitate ambitions in other career pathways (n = 46, 58%), improved patient care (n = 43, 54%), and having a pathway for combined hematologic/oncology and RO board certification (n = 46, 58%). In comparison to IM/RO, participants were significantly more interested in a combined RO and hematology/oncology program (median Likert-type rating 5, IQR 5-5, P = .005). Among the subgroup of 26 survey participants who believed it less likely they would apply for RO residency, 18 (69%) thought an IM/RO pathway would increase their interest in RO (median Likert-type rating 4, IQR 3-5). Interest in IM/RO did not differ by gender, race, or ethnicity. Conclusions: Combined training pathways involving RO were viewed positively by survey respondents, and may be particularly appealing to those less committed to a career in RO. Further research will help guide recommendations for the creation of these programs.

Radiation Therapy Summary of the AUA/ASTRO Guideline on Clinically Localized Prostate Cancer.

PURPOSE: Our purpose was to develop a summary of recommendations regarding the management of patients with clinically localized prostate cancer based on the American Urologic Association/ ASTRO Guideline on Clinically Localized Prostate Cancer. METHODS: The American Urologic Association and ASTRO convened a multidisciplinary, expert panel to develop recommendations based on a systematic literature review using an a priori defined consensus-building methodology. The topics covered were risk assessment, staging, risk-based management, principles of management including active surveillance, surgery, radiation, and follow-up after treatment. Presented are recommendations from the guideline most pertinent to radiation oncologists with an additional statement on health equity, diversity, and inclusion related to guideline panel composition and the topic of clinically localized prostate cancer. SUMMARY: Staging, risk assessment, and management options in prostate cancer have advanced over the last decade and significantly affect shared decision-making for treatment management. Current advancements and controversies discussed to guide staging, risk assessment, and treatment recommendations include the use of advanced imaging and tumor genomic profiling. An essential active surveillance strategy includes prostate-specific antigen monitoring and periodic digital rectal examination with changes triggering magnetic resonance imaging and possible biopsy thereafter and histologic progression or greater tumor volume prompting consideration of definitive local treatment. The panel recommends against routine use of adjuvant radiation therapy (RT) for patients with prostate cancer after prostatectomy with negative nodes and an undetectable prostate-specific antigen, while acknowledging that patients at highest risk of recurrence were relatively poorly represented in the 3 largest randomized trials comparing adjuvant RT to early salvage and that a role may exist for adjuvant RT in selected patients at highest risk. RT for clinically localized prostate cancer has evolved rapidly, with new trial results, therapeutic combinations, and technological advances. The recommendation of moderately hypofractionated RT has not changed, and the updated guideline incorporates a conditional recommendation for the use of ultrahypofractionated treatment. Health disparities and inequities exist in the management of clinically localized prostate cancer across the continuum of care that can influence guideline concordance.

Gender and the Receipt of the Association of Residents in Radiation Oncology Educator of the Year Award.

Purpose: We hypothesized that there may be a gender disparity in the receipt of the Association of Residents in Radiation Oncology (ARRO) Educator of the Year Award and sought to elucidate factors that contribute to differences in award receipt. Methods and Materials: Using a database provided by the American Society for Radiation Oncology, award recipients were identified from 2010 to 2022. Publicly available websites were accessed to obtain data regarding gender, years since residency graduation, percentage of female faculty, size of residency program, and program director designation. A 1-sample Z-test was used to assess whether the proportion of female ARRO award winners, defined as the proportion of female radiation oncology faculty members in the nominating universities that year, was significantly less than the population average. Secondary analyses used univariable binary logistic regression to identify global associations between gender, year since gradation, or program size. Results: The lowest proportion of female awardees occurred in 2013 (14.3%) and the greatest proportion in 2022 (30.6%). Compared with the proportion of female faculty members in nominating programs for the respective year, there were significantly fewer female awardees in 2010 (18% female awardees vs 32% female faculty members; P = .02) and 2013 (14% female awardees vs 31% female faculty members; P = .01). There was a statistically significant increase in female awardees during the study period (P < .01). On logistic regression analysis, large program size (≥10 residents) (odds ratio [OR], 6.86; 95% CI, 2.71-23.1; P < .001) and medium program size (5-9 residents) (OR, 4.05; 95% CI, 1.60-13.7; P < .001) were associated with a greater proportion of female awardees compared with small program size (1-4 residents). There was no association between awardee gender and years since graduation. Conclusions: A gender disparity was present in the receipt of ARRO Educator Awards. Residency chiefs, program directors, and chairs should work to ensure that a diverse slate of faculty is considered annually for the ARRO Educator Award.

Team Approach: Extremity Soft Tissue Sarcoma.

¼ Synovial sarcoma is a soft tissue sarcoma that most commonly presents in the extremity in a periarticular location.¼ As the history and physical examination of patients with synovial sarcoma can overlap considerably with those of patients with non-oncologic orthopedic conditions, it is important that orthopedic surgeons maintain a high level of suspicion when caring for patients with extremity masses.¼ Soft tissue sarcomas are best treated using a team approach. Early recognition and referral to a multidisciplinary sarcoma team are crucial to ensure the best clinical outcome for the patient.

Oncology Physician Workforce Diversity: Rationale, Trends, Barriers, and Solutions.

ABSTRACT: This chapter will discuss (1) the rationale for physician workforce diversity and inclusion in oncology; (2) current and historical physician workforce demographic trends in oncology, including workforce data at various training and career levels, such as graduate medical education and as academic faculty or practicing physicians; (3) reported barriers and challenges to diversity and inclusion in oncology, such as exposure, access, preparation, mentorship, socioeconomic burdens, and interpersonal, structural, systemic bias; and (4) potential interventions and evidence-based solutions to increase diversity, equity, and inclusion and mitigate bias in the oncology physician workforce.

Case-Matched Outcomes of Proton Beam and Intensity-Modulated Radiation Therapy for Localized Prostate Cancer.

Purpose: Although both intensity-modulated radiation therapy (IMRT) and proton beam therapy (PBT) offer effective long-term disease control for localized prostate cancer (PCa), there are limited data directly comparing the 2 modalities. Methods: The data from 334 patients treated with conventionally fractionated (79.2 GyRBE in 44 fractions) PBT or IMRT were retrospectively analyzed. Propensity score matching was used to balance factors associated with biochemical failure-free survival (BFFS). Age, race, and comorbidities (not BFFS associates) remained imbalanced after matching. Univariable and covariate-adjusted multivariable (MVA) Cox regression models were used to determine if modality affected BFFS. Results: Of 334 patients, 176 (52.7%) were included in the matched cohort with exact matching to National Comprehensive Cancer Network (NCCN) risk group. With a median follow-up time of 9.0 years (interquartile range [IQR]: 7.8-10.2 years), long-term BFFS was similar between the IMRT and PBT matched arms with 8-year estimates of 85% (95% CI: 76%-91%) and 91% (95% CI: 82%-96%, P = .39), respectively. On MVA, modality was not significantly associated with BFFS in both the unmatched (hazard ratio [HR] = 0.75, 95% CI: 0.35-1.63, P = .47) and matched (HR = 0.87, 95% CI: 0.33-2.33, P = .78) cohorts. Prostate cancer-specific survival (PCSS) and overall survival (OS) were also similar (P > .05). However, in an unmatched analysis, the PBT arm had significantly fewer incidences of secondary cancers within the irradiated field (0.6%, 95% CI: 0.0%-3.1% versus 4.5%, 95% CI: 1.8%-9.0%, P = .028). Conclusions: Both PBT and IMRT offer excellent long-term disease control for PCa, with no significant differences between the 2 modalities in BFFS, PCSS, and OS in matched patients. In the unmatched cohort, fewer incidences of secondary malignancy were noted in the PBT group; however, owing to overall low incidence of secondary cancer and imbalanced patient characteristics between the 2 groups, these data are strictly hypothesis generating and require further investigation.

Dose evaluation of inter- and intra-fraction prostate motion in extremely hypofractionated intensity-modulated proton therapy for prostate cancer.

Inter- and intra-fractional prostate motion can deteriorate the dose distribution in extremely hypofractionated intensity-modulated proton therapy. We used verification CTs and prostate motion data calculated from 1024 intra-fractional prostate motion records to develop a voxel-wise based 4-dimensional method, which had a time resolution of 1 s, to assess the dose impact of prostate motion. An example of 100 fractional simulations revealed that motion had minimal impact on planning dose, the accumulated dose in 95 % of the scenarios fulfilled the clinical goals for target coverage (D95 > 37.5 Gy). This method can serve as a complementary measure in clinical setting to guarantee plan quality.

Comparative In Silico Analysis of Ultra-Hypofractionated Intensity-Modulated Photon Radiotherapy (IMRT) Versus Intensity-Modulated Proton Therapy (IMPT) in the Pre-Operative Treatment of Retroperitoneal Sarcoma.

BACKGROUND: While pre-operative radiation did not improve abdominal recurrence-free survival for retroperitoneal sarcoma (RPS) in the randomized STRASS trial, it did reduce rates of local recurrence. However, the risk of toxicity was substantial and the time to surgery was prolonged. A combination of hypofractionation and proton therapy may reduce delays from the initiation of radiation to surgery and limit the dose to surrounding organs at risk (OARs). We conducted a dosimetric comparison of the pre-operative ultra-hypofractionated intensity-modulated photon (IMRT) and proton radiotherapy (IMPT). METHODS: Pre-operative IMRT and IMPT plans were generated on 10 RPS patients. The prescription was 25 Gy radiobiological equivalents (GyEs) (radiobiological effective dose of 1.1) to the clinical target volume and 30 GyEs to the margin at risk, all in five fractions. Comparisons were made using student T-tests. RESULTS: The following endpoints were significantly lower with IMPT than with IMRT: mean doses to liver, bone, and all genitourinary and gastrointestinal OARs; bowel, kidney, and bone V5-V20; stomach V15; liver V5; maximum doses to stomach, spinal canal, and body; and whole-body integral dose. CONCLUSIONS: IMPT maintained target coverage while significantly reducing the dose to adjacent OARs and integral dose compared to IMRT. A prospective trial treating RPS with pre-operative ultra-hypofractionated IMPT at our institution is currently being pursued.

In silico comparison of whole pelvis intensity-modulated photon versus proton therapy for the postoperative management of prostate cancer.

BACKGROUND: Limited data exist comparing intensity-modulated photon (IMRT) and proton (IMPT) radiation therapy when treating the prostate bed and pelvic lymph nodes in the postoperative setting for prostate cancer. The aim of this study was to evaluate dosimetric differences between IMRT and IMPT when treating with whole pelvis radiation therapy (WPRT) postoperatively. MATERIALS AND METHODS: IMRT and IMPT plans were generated for 10 post-prostatectomy patients treated between July and August 2020. The prescription was 50 Gy radiobiologic equivalent (GyE) (proton radiobiological effective dose 1.1) to the pelvis and 70 GyE to the prostate bed in 2 GyE per fraction. Paired 2-sided Wilcoxon signed-rank tests were used to compare clinical target volume (CTV) coverage and dose to organs at risk (OARs). RESULTS: CTV coverage was met for all plans with 99% of CTVs receiving ≥99% of prescription doses. Dose to OARs was significantly higher with IMRT than IMPT for the following endpoints: bladder V5-V65; bowel V5-V45; sigmoid V5-V50; rectum V5-V70; femoral head V40 and maximum dose; bone V5-V65. Select endpoints with significant differences included bladder V30 (63.5 vs. 44.4%, p < .001), bowel V15 (949 vs. 191 cc, p = .001) and V30 (386 vs. 121 cc, p < .001), rectum V40 (81.8 vs. 32.1%, p < .001) and V50 (47.6 vs. 24.9%, p < .001), femoral head maximum doses (46.4-47.1 vs. 38.3-38.6GyE, p < .001), and bone V10 (93.3 vs. 85.4%, p < . 001). Mean doses for all OARs were significantly higher with IMRT, including bladder (41.9 vs. 29.7GyE, p < .001), bowel (21.2 vs. 5.5GyE, p < .001), and rectum (50.8 vs. 27.3GyE, p < .001). Integral dose to 'Body - CTV' was significantly higher with IMRT (32.8 vs. 18.4 J, p < .001). CONCLUSION: IMPT provides comparable target coverage to IMRT when treating prostate cancer with WPRT in the postoperative setting while significantly reducing dose to OARs. These data can inform the future clinical management and delivery of post-prostatectomy irradiation for prostate cancer.

Radiotherapy Deserts: The Impact of Race, Poverty, and the Rural-Urban Continuum on Density of Providers and the Use of Radiation Therapy in the US.

PURPOSE: Prior efforts to characterize disparities in radiation therapy access and receipt have not comprehensively investigated interplay between race, socioeconomic status, and geography relative to oncologic outcomes. This study sought to define these complex relationships at the US county level for prostate cancer (PC) and invasive breast (BC) cancer to build a tool that facilitates identification of "radiotherapy deserts"-regions with mismatch between radiation therapy resources and oncologic need. METHODS AND MATERIALS: An ecologic study model was constructed using national databases to evaluate 3,141 US counties. Radiation therapy resources and use densities were operationalized as physicians to persons at risk (PPR) and use to persons at risk (UPR): the number of attending radiation oncologists and Medicare beneficiaries per 100,000 persons at risk, respectively. Oncologic need was defined by "hot zone" counties with ≥2 standard deviations (SDs) above mean incidence and death rates. Univariable and multivariable logistic regressions examined links between PPR and UPR densities, epidemiologic variables, and hot zones for oncologic outcomes. Statistics are reported at a significance level of P < .05. RESULTS: The mean (SD) PPR and UPR densities were 2.1 (5.9) and 192.6 (557.6) for PC and 1.9 (5.3) and 174.4 (501.0) for BC, respectively. Counties with high PPR and UPR densities were predominately metropolitan (odds ratio [OR], 2.9-4.4), generally with a higher percentage of Black non-Hispanic constituents (OR, 1.5-2.3). Incidence and death rate hot zones were largely nonmetropolitan (OR, 0.3-0.6), generally with a higher percentage of Black non-Hispanic constituents (OR, 3.2-6.3). Lower PPR density was associated with death rate hot zones for both types of cancer (OR, 0.8-0.9); UPR density was generally not linked to oncologic outcomes on multivariable analysis. CONCLUSIONS: The study found that mismatch between oncologic need with PPR and UPR disproportionately affects nonmetropolitan communities with a higher percentage of Black non-Hispanic constituents. An interactive web platform (bit.ly/densitymaps) was developed to visualize "radiotherapy deserts" and drive targeted investigation of underlying barriers to care in areas of highest need, with the goal of reducing health inequities in this context.

Radiation Oncology Residency Training Program Integration of Diversity, Equity, and Inclusion: An Association of Residents in Radiation Oncology Equity and Inclusion Subcommittee Inaugural Program Director Survey.

PURPOSE: The aim of this study was to investigate United States (US) radiation oncology (RO) program directors' (PDs) attitudes and practices regarding racial/ethnic diversity, equity, and inclusion (DEI) to better understand potential effects on underrepresented in medicine (UIM) residents in RO. METHODS AND MATERIALS: A 28-item survey was developed using the validated Ethnic Harassment Experiences Scale and the Daily Life Experiences subscale, as well as input from DEI leaders in RO. The survey was institutional review board-approved and administered to RO PDs. PDs were provided with the American Association of Medical Colleges definition of UIM, that is, "Underrepresented in medicine means those racial and ethnic populations that are underrepresented in the medical profession relative to their numbers in the general population." Descriptive statistics were used in analysis. RESULTS: The response rate was 71% (64/90). Institutional Culture and Beliefs: 42% responded that they had a department DEI director. A minority (17%, n = 11) agreed "I believe that people from UIM backgrounds have equal access to quality tertiary education in the US." The majority (97%, n = 62) agreed "My program values residents from UIM backgrounds." Support and Resources: The majority (78%, n = 50) agreed "My program has resources in place to assist/provide support for resident physicians from UIM backgrounds." Interview and Recruitment: Most PDs (53%) had not taken part in activities aimed at recruiting UIM residents and 17% had interviewed no UIM applicants in the past 5 years for residency. Resident Experiences of Racism: 17% (n = 11) agreed "UIM residents in my program have reported incidents of racism to me," and 28% (n = 18) agreed "I believe that UIM residents in my program have been treated differently because of their race/ethnicity by faculty, staff, coresidents or patients." CONCLUSIONS: Most PDs reported that they did not believe that UIM residents were treated differently in their department because of their race/ethnicity, and only a minority had received reports of racial discrimination experienced by residents. These data contrast resident experiences and suggest a disconnect between DEI perceptions and resident experiences among US RO PDs that should be addressed through increased programmatic action and evaluation.

Comparing Ultra-hypofractionated Proton versus Photon Therapy in Extremity Soft Tissue Sarcoma.

Purpose: Recent single institution, phase II evidence has demonstrated the feasibility and efficacy of ultra-hypofractionated, preoperative photon therapy in 5 fractions for the treatment of soft tissue sarcoma (STS). Our purpose was to evaluate the dosimetric benefits of modern scanning beam proton therapy compared with conventional photon radiation therapy (RT) for the neoadjuvant treatment of adult extremity STS. Materials and Methods: Existing proton and photon plans for 11 adult patients with STS of the lower extremities previously treated preoperatively with neoadjuvant RT at our center were used to create proton therapy plans using Raystation Treatment Planning System v10.A. Volumes were delineated, and doses reported consistent with International Commission on Radiation Units and Measurements reports 50, 62, and 78. Target volumes were optimized such that 100% clinical target volume (CTV) was covered by 99% of the prescription dose. The prescribed dose was 30 Gy for PT and RT delivered in 5 fractions. For proton therapy, doses are reported in GyRBE = 1.1 Gy. The constraints for adjacent organs at risk (OARs) within 1 cm of the CTV were the following: femur V30Gy ≤ 50%, joint V30Gy < 50%, femoral head V30Gy ≤ 5 cm3, strip V12 ≤ 10%, and skin V12 < 50%. Target coverage goals, OAR constraints, and integral dose were compared by Student t test with P < .05 significance. Results: A minimum 99% CTV coverage was achieved for all plans. OAR dose constraints were achieved for all proton and photon plans; however, mean doses to the femur (10.7 ± 8.5 vs 16.1 ± 7.7 GyRBE), femoral head (2.0 ± 4.4 vs 3.6 ± 6.4 GyRBE), and proximal joint (1.8 ± 2.4 vs 3.5 ± 4.4 GyRBE) were all significantly lower with PT vs intensity-modulated radiation therapy (IMRT) (all P < .05). Integral dose was significantly reduced for proton vs photon plans. Conformity and heterogeneity indices were significantly better for proton therapy. Conclusion: Proton therapy maintained target coverage while significantly reducing integral and mean doses to the proximal organs at risk compared with RT. Further prospective investigation is warranted to validate these findings and potential benefit in the management of adult STS.

Treatment Planning of Bulky Tumors Using Pencil Beam Scanning Proton GRID Therapy.

Purpose: To compare spatially fractionated radiation therapy (GRID) treatment planning techniques using proton pencil-beam-scanning (PBS) and photon therapy. Materials and Methods: PBS and volumetric modulated arc therapy (VMAT) GRID plans were retrospectively generated for 5 patients with bulky tumors. GRID targets were arranged along the long axis of the gross tumor, spaced 2 and 3 cm apart, and treated with a prescription of 18 Gy. PBS plans used 2- to 3-beam multiple-field optimization with robustness evaluation. Dosimetric parameters including peak-to-edge ratio (PEDR), ratio of dose to 90% of the valley to dose to 10% of the peak VPDR(D90/D10), and volume of normal tissue receiving at least 5 Gy (V5) and 10 Gy (V10) were calculated. The peak-to-valley dose ratio (PVDR), VPDR(D90/D10), and organ-at-risk doses were prospectively assessed in 2 patients undergoing PBS-GRID with pretreatment quality assurance computed tomography (QACT) scans. Results: PBS and VMAT GRID plans were generated for 5 patients with bulky tumors. Gross tumor volume values ranged from 826 to 1468 cm3. Peak-to-edge ratio for PBS was higher than for VMAT for both spacing scenarios (2-cm spacing, P = .02; 3-cm spacing, P = .01). VPDR(D90/D10) for PBS was higher than for VMAT (2-cm spacing, P = .004; 3-cm spacing, P = .002). Normal tissue V5 was lower for PBS than for VMAT (2-cm spacing, P = .03; 3-cm spacing, P = .02). Normal tissue mean dose was lower with PBS than with VMAT (2-cm spacing, P = .03; 3-cm spacing, P = .02). Two patients treated using PBS GRID and assessed with pretreatment QACT scans demonstrated robust PVDR, VPDR(D90/D10), and organs-at-risk doses. Conclusions: The PEDR was significantly higher for PBS than VMAT plans, indicating lower target edge dose. Normal tissue mean dose was significantly lower with PBS than VMAT. PBS GRID may result in lower normal tissue dose compared with VMAT plans, allowing for further dose escalation in patients with bulky disease.