Axillary Surgery for Chemoresidual (ypN-Positive) Nodal Disease

This cohort study using pooled data from 2 randomized clinical trials examines whether removing more lymph nodes with axillary lymph node dissection improved outcomes over sentinel lymph node biopsy when most patients received adjuvant radiation therapy or regional nodal irradiation.

Effects on Lung Tissue After Breast Cancer Radiation: Comparing Photon and Proton Therapies

Purpose

In breast cancer, improved treatment approaches that reduce injury to lung tissue and early diagnosis and intervention for lung toxicity are increasingly important in survivorship. The aims of this study are to (1) compare lung tissue radiographic changes in women treated with conventional photon radiation therapy and those treated with proton therapy (PT), (2) assess the volume of lung irradiated to 5 Gy (V5) and 20 Gy (V20) by treatment modality, and (3) quantify the effects of V5, V20, time, and smoking history on the severity of tissue radiographic changes.

Patients and Methods

A prospective observational study of female breast cancer patients was conducted to monitor postradiation subclinical lung tissue radiographic changes. Repeated follow-up x-ray computed tomography scans were acquired through 2 years after treatment. In-house software was used to quantify an internally normalized measure of pulmonary tissue density change over time from the computed tomography scans, emphasizing the 6- and 12-month time points.

Results

Compared with photon therapy, PT was associated with significantly lower lung V5 and V20. Lung V20 (but not V5) correlated significantly with increased subclinical lung tissue radiographic changes 6 months after treatment, and neither correlated with lung effects at 12 months. Significant lung tissue density changes were present in photon therapy patients at 6 and 12 months but not in PT patients. Significant lung tissue density change persisted at 12 months in ever-smokers but not in never-smokers.

Conclusion

Patients treated with PT had significantly lower radiation exposure to the lungs and less statistically significant tissue density change, suggesting decreased injury and/or improved recovery compared to photon therapy. These findings motivate additional studies in larger, randomized, and more diverse cohorts to further investigate the contributions of treatment modality and smoking regarding the short- and long-term radiographic effects of radiation on lung tissue.

Consolidative Proton Radiotherapy for Pediatric Extramedullary Ocular Acute Myeloid Leukemia

Purpose

Pediatric acute myeloid leukemia (AML) often involves extramedullary sites, which can be resistant to standard induction chemotherapy. Consolidative radiation therapy can be used in select cases to improve local control rates and help bridge patients to curative stem cell transplants. However, there is no previously published data to support the use of proton radiotherapy (PT) in this setting. We present radiographic findings and pathologic outcomes of the first reported patient with extramedullary ocular AML to be treated with PT.

Patients and Methods

Details regarding diagnostic evaluation and treatment were obtained from the electronic medical records at the University of Florida Proton Therapy Institute, Nemours Children's Health, and St. Joseph's Children's Hospital.

Results

This 7-month-old patient presented with biopsy-proven relapsed AML in the bilateral anterior chambers of the eyes, which did not resolve with induction chemotherapy. The patient then received PT to a dose of 24 cobalt gray equivalent to both eyes and was found to have no evidence of disease following treatment.

Conclusion

This case provides further evidence that consolidative radiotherapy may be considered for select patients with extramedullary AML who have limited response to induction chemotherapy. Given the increased prevalence of extramedullary AML in pediatric patients, it is worth considering the utilization of PT to mitigate damage to nearby organs and the risk of secondary malignancies.

Outcomes following proton therapy for pediatric esthesioneuroblastoma

BACKGROUND

Pediatric esthesioneuroblastoma (EN) can infiltrate skull base anatomy, presenting challenges due to high radiation doses and pediatric tissue sensitivity. This study reports outcomes of pediatric EN treated with proton radiotherapy (PT).

PROCEDURE

Using an IRB-approved prospective outcomes registry, we evaluated patient, tumor, and treatment-related variables impacting disease control and toxicity in pediatric nonmetastatic EN treated with modern multimodality therapy, including PT.

RESULTS

Fifteen consecutive patients (median age 16) comprising Kadish stage B (n = 2), C (n = 9), and D (n = 4) tumors were assessed, including six with intracranial involvement, four with cranial nerve deficits, and four with cervical lymphadenopathy. Before radiation, two had subtotal and 13 had gross total resections (endoscopic or craniofacial). Two underwent neck dissection. Eleven received chemotherapy before radiation (n = 5), concurrent with radiation (n = 4), or both (n = 2). Median total radiation dose (primary site) was 66 Gy/CGE for gross disease and 54 Gy/CGE (cobalt Gray equivalent) for microscopic disease. Median follow-up was 4.8 years. No patients were lost to follow-up. Five-year disease-free and overall survival rates were 86% (no local or regional recurrences). Two patients developed vertebral metastases and died. Two required a temporary feeding tube for oral mucositis/dysphagia. Late toxicities included symptomatic retinopathy, major reconstructive surgery, cataracts, chronic otitis media, chronic keratoconjunctivitis, hypothyroidism, and in-field basal cell skin cancer.

CONCLUSIONS

A multimodality approach for pediatric EN results in excellent local control. Despite the moderate-dose PT, serious radiation toxicity was observed; further dose and target volume reductions may benefit select patients. Longer follow-up and comparative data from modern photon series are necessary to fully characterize any relative PT advantage.

Proton Therapy in the Treatment of Men with Breast Cancer

Purpose

Male breast cancer treatment involves multimodality therapy, including radiation therapy; nevertheless, few men have received proton therapy (PT) for it. Further, heart disease is an established leading cause of death in men, and radiation therapy heart dose correlates with cardiac toxicity, highlighting the need for cardiac-sparing radiation techniques. Thus, we provide a descriptive analysis of PT in a male breast cancer cohort.

Patients and Methods

Men who received PT for localized breast cancer between 2012 and 2022 were identified from a prospective database. Toxicities were prospectively recorded by using the Common Terminology Criteria for Adverse Events (CTCAE), version 4.0.

Results

Five male patients were identified. All had estrogen receptor (ER)-positive, Her2neu-negative disease and received adjuvant endocrine therapy. One had genetic testing positive for BRCA2, one had a variant of unknown significance (VUS) in the APC gene, and one had a VUS in MSH2. Median age was 73 years (range, 41-80). Baseline comorbidities included obesity (n = 1), diabetes (n = 1), hypertension (n = 4), history of deep vein thrombosis (n = 1), personal history of myocardial infarction (n = 3; 1 with a pacemaker), and a history of lung cancer (n = 1). All received PT to the left chest wall and comprehensive regional lymphatics. One received passive-scattering PT, and 4 received pencil beam scanning. One patient received a boost to the mastectomy incision via electrons. Median heart dose was 1 GyRBE (range, 0-1.0), median 0.1-cm3 dose to the left anterior descending artery was 7.5 GyRBE (range, 0-14.2), and median follow-up was 2 years (range, 0.75-6.5); no patient experienced a new cardiac event, and all remain free from breast cancer recurrence and progression.

Conclusion

In a small case series for a rare diagnosis, PT to the chest wall and regional lymphatics, including internal mammary nodes, resulted in low cardiac exposure, high local regional disease control rates, and minimal toxicity. Proton therapy should be considered for treating men with breast cancer to achieve cardiac sparing.

Palliative care utilization and racial and ethnic disparities among women with de novo metastatic breast cancer in the United States

PURPOSE

The potential disparities in palliative care delivery for underrepresented minorities with breast cancer are not well known. We sought to determine whether race and ethnicity impact the receipt of palliative care for patients with metastatic breast cancer (MBC).

METHODS

We retrospectively reviewed the National Cancer Database for female patients diagnosed with stage IV breast cancer between 2010 and 2017 who received palliative care following diagnosis of MBC to assess the proportion of patients who received palliative care, including non-curative-intent local-regional or systemic therapy. Multivariable logistic regression analysis was performed to identify variables associated with receiving palliative care.

RESULTS

60,685 patients were diagnosed with de novo MBC. Of these, only 21.4% (n = 12,963) received a palliative care service. Overall, there was a positive trend in palliative care receipt from 18.2% in 2010 to 23.0% in 2017 (P < 0.001), which persisted when stratified by race and ethnicity. Relative to non-Hispanic White women, Asian/Pacific Islander women (aOR 0.80, 95% CI 0.71-0.90, P < 0.001), Hispanic women (adjusted odds ratio [aOR] 0.69, 95% CI 0.63-0.76, P < 0.001), and non-Hispanic Black women (aOR 0.94, 95% CI 0.88-0.99, P = 0.03) were less likely to receive palliative care.

CONCLUSIONS

Fewer than 25% of women with MBC received palliative care between 2010 and 2017. While palliative care has significantly increased for all racial/ethnic groups, Hispanic White, Black, and Asian/Pacific Islander women with MBC still receive significantly less palliative care than non-Hispanic White women. Further research is needed to identify the socioeconomic and cultural barriers to palliative care utilization.

Analysis of the Pediatric Radiotherapy Landscape in Mexico and a Subsequent Educational e-Contouring Intervention

PURPOSE

Mexico and Central America have the highest childhood cancer incidence in the West. Pediatric-specific oncology knowledge contributes to the disparity. We sought to (1) determine the self-identified treatment patterns and needs of Mexican pediatric radiation oncologists and (2) pilot a workshop to improve contouring accuracy.

MATERIALS AND METHODS

Partnering with local experts and the Sociedad Mexicana de Radioterapeutas (SOMERA), a 35-question survey was designed to ascertain pediatric radiotherapy capacity and distributed through the SOMERA listserv. The most challenging malignancies were selected for workshop. Participants received precontouring and postcontouring homework to assess improvement per the Dice metric. The Wilcoxon sign-rank test was used for comparative statistics.

RESULTS

Ninety-four radiation oncologists attempted and 79 completed the survey. Forty-four (76%) felt comfortable treating a pediatric patient, and 36 (62%) were familiar with national protocols for pediatric treatment. Most had access to nutrition, rehabilitation, endocrinology, and anesthesia; 14% had access to fertility services and 27% to neurocognitive support; 11% noted no support, and only one respondent had child-life support. The postsurvey contouring workshop was conducted for high-grade glioma, medulloblastoma, and Hodgkin lymphoma. Significant improvements were seen in all target volumes.

CONCLUSION

We present the first national survey of Mexico's pediatric radiotherapy capacity and Latin American e-contouring educational intervention with preworkshop and postworkshop Dice metrics, noting statistically significant improvement in all target volumes. Participation improved compared with prior experience through SOMERA partnership and Continuing Medical Education incentivization.

Racial and Ethnic Demographic Reporting in Phase 2 Proton Therapy Clinical Trials: A Review

Purpose

Equitable inclusion of racial and ethnic participation in clinical trials is crucial to improving disparities in health care, especially for historically marginalized populations. Our study aims to describe the racial and ethnic demographics of patients enrolled in published phase 2 clinical trials involving proton therapy in the United States.

Materials and Methods

Published manuscripts were identified in PubMed, Embase, World of Science, and Cochrane. Phase 2 trials evaluating proton therapy for US patients were included. For each article in the study, data were collected comprising authors, title, and publication year, and clinical trial numbers were verified. Additional data included tumor site, primary institution, sample size, reported race/ethnicity, and raw number/percentile of race/ethnicity. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were used.

Results

Overall, 970 titles were identified; 636 remained after duplicate screening, and 75 full-text articles were assessed. We identified 38 eligible manuscripts for inclusion comprising 2648 patients. Only 15 (39%) of the publications reported race/ethnicity. Of these, 8 (21%) and 10 (26%) documented Hispanic or Black trial participants, respectively; however, only 6 (16%) documented trial participation for both Hispanic and Black patients. Of the 1409 patients with a documented race/ethnicity, 89.0% (n = 1254) were non-Hispanic white, 5.3% (n = 75) were Black, and 2.2% (n = 31) were Hispanic. Other and unknown race/ethnicity comprised the remaining patients (3.5%; n = 49).

Conclusion

We identified underreporting of demographic data in published phase 2 proton therapy trials, which unfortunately mirrored underreporting for cancer drug clinical trials. We also noted dramatic Black and Hispanic patient underrepresentation across the trials in which race and ethnicity are reported. Findings highlight the urgent need to identify and address barriers to proton therapy trials for Black and Hispanic patients ensuring clinical trials in radiation oncology are representative of the patients seen in clinical practice.

Proton Therapy for Bilateral Breast Cancer Maximizes Normal-Tissue Sparing

Purpose

Treatment for bilateral breast cancer with radiation therapy is technically challenging. We evaluated the clinical and dosimetric outcomes of a small series of patients with synchronous bilateral breast cancer, including a photon dosimetric comparison, to identify optimal treatment planning approaches.

Materials and Methods

We reviewed a registry of patients (simultaneously) diagnosed with synchronous bilateral breast cancers who underwent postoperative definitive adjuvant proton therapy at our institution between 2012 and 2021. All patients were treated with double-scattered proton or pencil-beam scanning therapies. For comparison, intensity-modulated radiation therapy photon plans optimized for organ sparing and coverage were generated after treatment.

Results

Six patients were included. The median patient age was 66 years; all were female with no history of breast cancer or radiation therapy. Two (33%) patients received breast/chest wall–only treatments, 1 (17%) required breast plus level I axillary treatment to one side and breast plus regional nodal irradiation (RNI) to the other, and 3 (50%) received bilateral breast/chest plus RNI; dosimetric results are reported for each group's median. Analysis showed clinical target coverage was comparable between proton and photon techniques (V95% of 96.4% with proton, 97.8% with photon). However, protons could deliver superior organ sparing at clinically relevant dose metrics for virtually all structures: a 6.7 Gy absolute reduction in the mean heart dose (7.5 Gy with photons to 0.7 Gy with protons), a 47% to 57% relative reduction in D0.1cm3 to coronary arteries, a 54% relative reduction in lung V20 Gy, and an absolute 7.6 Gy reduction to the brachial plexus. There was also greater esophagus and spinal cord sparing. The overall survival rate was 100% at 1.5 years of median follow-up (0.5-4.9), and all patients were free of disease. For toxicity, all patients had some form of acute side effects: 66% experienced grade 2 breast/chest pain or soreness; 100% had grade 2 radiation dermatitis or skin induration; 33% had grade 2 fatigue; and 17% had grade 2 esophagitis (per the Common Terminology Criteria for Adverse Events [CTCAE] version 5.0; US National Cancer Institute, Bethesda, Maryland). Subacute toxicity (within 6 months) was observed for 17% of patients with delayed onset of grade 3 dermatitis in the setting of preexisting lupus, 17% with a delayed surgical wound complication, and 17% with grade 2 soft tissue fibrosis. No grade 4 or 5 events were observed.

Conclusions

Substantial dose reductions to multiple organs at risk while maintaining target coverage make proton the preferred modality for bilateral breast cancer treatment when available.

Incidence of Rib Fracture following Treatment with Proton Therapy for Breast Cancer

Purpose

To determine the rib fracture rate in a cohort of patients with breast cancer treated with proton therapy.

Patient and Methods

From a prospective database, we identified 225 patients treated with proton therapy between 2012 and 2020 (223 women; 2 men). Clinical and dosimetric data were extracted, the cumulative incidence method assessed rib fracture rate, and Fine-Gray tests assessed prognostic significance of select variables. In-field rib fracture was defined as a fracture that occurred in a rib located within the 10% isodose line. Out-of-field rib fracture was defined as a fracture occurring in a rib location outside of the 10% isodose line.

Results

Of the patients, 74% had left-sided breast cancer; 5%, bilateral; and 21%, right-sided. Dual-energy x-ray absorptiometry scans showed normality in 20%, osteopenia in 34%, and osteoporosis in 6% (test not performed in 40%). Additionally, 57% received an aromatase inhibitor. Target volumes were breast ± internal mammary nodes (IMNs) (16%), breast and comprehensive regional lymphatics (32%), chest wall ± IMNs (1%), and chest wall/comprehensive regional lymphatics (51%). Passive-scattered proton therapy was used for 41% of patients, 58% underwent pencil-beam scanning (PBS), and 1% underwent a combination (passive scattering/PBS), with 85% of patients receiving a boost. Median follow-up was 3.1 years, with 97% having >12-month follow-up. The 3-year cumulative in-field rib fracture incidence was 3.7%. Eight patients developed in-field rib fractures (1 symptomatic, 7 imaging identified) for a 0.4% symptomatic rib fracture rate. Median time from radiation completion to rib fracture identification was 1.8 years (fractures were identified within 2.2 years for 7 of 8 patients). No variables were associated with rib fracture on univariate analysis. Three fractures developed outside the radiation field (0.9% cumulative incidence of out-of-field rib fracture).

Conclusion

In this series of patients with breast cancer treated with proton therapy, the 3-year rib fracture rates remain low (in-field 3.7%; symptomatic 0.4%). As in photon therapy, the asymptomatic rate may be underestimated owing to a lack of routine surveillance imaging. However, patients experiencing symptomatic rib fractures after proton therapy for breast cancer are rare.

Global and regional estimates of orphans attributed to maternal cancer mortality in 2020

Despite women being disproportionally affected by cancer deaths at young ages, there are no global estimates of the resulting maternal orphans, who experience health and education disadvantages throughout their lives. We estimated the number of children who became maternal orphans in 2020 due to their mother dying from cancer in that year, for 185 countries worldwide and by cause of cancer-related death. Female cancer deaths-by country, cancer type and age (derived from GLOBOCAN estimates)-were multiplied by each woman's estimated number of children under the age of 18 years at the time of her death (fertility data were derived from United Nations World Population Prospects for birth cohort), accounting for child mortality and parity-cancer risk associations. Globally, there were 1,047,000 such orphans. Over half of these were orphans due to maternal deaths from breast (258,000, 25%), cervix (210,000, 20%) and upper-gastrointestinal cancers (136,000, 13%), and most occurred in Asia (48%: India 15%, China 10%, rest of Asia 23%) and Africa (35%). Globally, there were 40 new maternal orphans due to cancer per 100,000 children, with a declining trend with a higher Human Development Index (range: 121 in Malawi to 15 in Malta). An estimated 7 million children were prevalent maternal orphans due to cancer in mid-2020. Accelerating the implementation of the World Health Organization's cervical and breast cancer initiatives has the potential to avert not only millions of preventable female cancer deaths but also the associated, often-overlooked, intergenerational consequences of these deaths.

Intraoperative radiation therapy for early-stage breast cancer: a single-institution experience

Background

To assess outcomes and toxicity after low-energy intraoperative radiotherapy (IORT) for early-stage breast cancer (ESBC).

Materials and methods

We reviewed patients with unilateral ESBC treated with breast-conserving surgery and 50-kV IORT at our institution. Patients were prescribed 20 Gy to the surface of the spherical applicator, fitted to the surgical cavity during surgery. Patients who did not meet institutional guidelines for IORT alone on final pathology were recommended adjuvant treatment, including additional surgery and/or external-beam radiation therapy (EBRT). We analyzed ipsilateral breast tumor recurrence, overall survival, recurrence-free survival and toxicity.

Results

Among 201 patients (median follow-up, 5.1 years; median age, 67 years), 88% were Her2 negative and ER positive and/or PR positive, 98% had invasive ductal carcinoma, 87% had grade 1 or 2, and 95% had clinical T1 disease. Most had pathological stage T1 (93%) N0 (95%) disease. Mean IORT applicator dose at 1-cm depth was 6.3 Gy. Post-IORT treatment included additional surgery, 10%; EBRT, 11%; adjuvant chemotherapy, 9%; and adjuvant hormonal therapy, 74%. Median total EBRT dose was 42.4 (range, 40.05–63) Gy and median dose per fraction was 2.65 Gy. At 5 years, the cumulative incidence of ipsilateral breast tumor recurrence was 2.7%, the overall survival rate was 95% with no breast cancer-related deaths, and the recurrence-free survival rate was 96%. For patients who were deemed unsuitable for postoperative IORT alone and did not receive recommended risk-adapted EBRT, the IBTR rate was 4.7% versus 1.7% (p = 0.23) for patients who were either suitable for IORT alone or unsuitable and received adjuvant EBRT. Cosmetic toxicity data was available for 83%, with 7% experiencing grade 3 breast toxicity and no grade 4–5 toxicity.

Conclusions

IORT for select patients with ESBC results in acceptable outcomes in regard to ipsilateral breast tumor recurrence and toxicity.

RBE-weighted dose and its impact on the risk of acute coronary event for breast cancer patients treated with intensity modulated proton therapy

PURPOSE

To evaluate the relative biological effectiveness (RBE)-weighted dose to the heart and to estimate RBE uncertainties when assuming a constant RBE of 1.1, for breast cancer patients receiving intensity-modulated proton therapy (IMPT). Further, to study the impact of RBE uncertainties on the risk of an acute coronary event (ACE).

MATERIAL AND METHODS

We analyzed 20 patients who received IMPT to either the left breast (n = 10) or left chest wall (n = 10) and regional lymph nodes. The Monte Carlo simulation engine, MCsquare, was used to simulate the dose-averaged linear energy transfer (LETd) map. The RBE-weighted dose to the heart and its substructures was calculated using three different RBE models. The risk of ACE was estimated per its linear relationship with mean heart dose (MHD) as established by Darby et al.

RESULTS

The median MHD increased from 1.33 GyRBE assuming an RBE of 1.1 to 1.64, 1.87, and 1.99 GyRBE when using the RBE-weighted dose models. The median values (and ranges) of the excess absolute risk of ACE were 0.4% (0.1%-0.8%) when assuming an RBE of 1.1, and 0.6% (0.2%-1.0%), 0.6% (0.2%-1.1%), and 0.7% (0.2%-1.1%) with the RBE-weighted models. For our patient cohort, the maximum excess absolute risk of ACE increased by 0.3% with the RBE-weighted doses compared to the constant RBE of 1.1, reaching an excess absolute ACE risk of 1.1%. The interpatient LETd variation was small for the relevant high-dose regions of the heart.

CONCLUSION

All three RBE models predicted a higher biological dose compared to the clinical standard dose assuming a constant RBE of 1.1. An underestimation of the biological dose results in underestimation of the ACE risk. Analyzing the voxel-by-voxel biological dose and the LET map alongside clinical outcomes is warranted in the development of a more accurate normal-tissue complication probability model.

Demographics of ASTRO Student Members and Potential Implications for Future U.S. Radiation Oncology Workforce Diversity

Purpose

The radiation oncology workforce in the United States is comparatively less diverse than the U.S. population and U.S. medical school graduates. Workforce diversity correlates with higher quality care and outcomes. The purpose of this study was to determine whether student members of the American Society for Radiation Oncology (ASTRO) are any more diverse than resident members-in-training using the recently established medical student membership category.

Methods and Materials

Self-reported sex, race and Hispanic ethnicity, medical school, and degree(s) earned for all medical students (n = 268) and members-in-training (n = 713) were collected from the ASTRO membership database. International members were excluded. The χ² test was used to assess for differences between subgroups.

Results

Compared with members-in-training, student members were more likely to be female (40.0% vs 31.5%, P = .032), black or African American (10.7% vs 4.8%, P = .009), candidates for or holders of a DO rather than MD degree (5.2% vs 1.5%, P = .002), and from a U.S. medical school that is not affiliated with a radiation oncology residency program (30.5% vs 20.9%, P = .001). There was no significant difference in self-reported Hispanic ethnicity (7.3% vs 5.4%, P = .356). There were no indigenous members in either category assessed.

Conclusions

Medical student members of ASTRO are more diverse in terms of black race, female sex, and osteopathic training, though not in terms of Hispanic ethnicity or nonmultiracial indigenous background, than the members-in-training. Longitudinal engagement with these students and assessment of the factors leading to specialty retention versus attrition may increase diversity, equity, and inclusion in radiation oncology.

Heterogeneity in Radiotherapeutic Parameter Assumptions in Cost-Effectiveness Analyses in Prostate Cancer: A Call for Uniformity

OBJECTIVES

Cost-effectiveness analyses (CEAs) may provide useful data to inform management decisions depending on the robustness of a model's input parameters. We sought to determine the level of heterogeneity in health state utility values, transition probabilities, and cost estimates across published CEAs assessing primarily radiotherapeutic management strategies in prostate cancer.

METHODS

We conducted a systematic review of prostate cancer CEAs indexed in MEDLINE between 2000 and 2018 comparing accepted treatment modalities across all cancer stages. Search terms included "cost effectiveness prostate," "prostate cancer cost model," "cost utility prostate," and "Markov AND prostate AND (cancer OR adenocarcinoma)." Included studies were agreed upon. A Markov model was designed using the parameter estimates from the systematic review to evaluate the effect of estimate heterogeneity on strategy cost acceptability.

RESULTS

Of 199 abstracts identified, 47 publications were reviewed and 37 were included; 508 model estimates were compared. Estimates varied widely across variables, including gastrointestinal toxicity risk (0%-49.5%), utility of metastatic disease (0.25-0.855), intensity-modulated radiotherapy cost ($21 193-$61 996), and recurrence after external-beam radiotherapy (1.5%-59%). Multiple studies assumed that different radiotherapy modalities delivering the same dose yielded varying cancer control rates. When using base estimates for similar parameters from included studies, the designed model resulted in 3 separate acceptability determinations.

CONCLUSIONS

Significant heterogeneity exists across parameter estimates used to perform CEAs evaluating treatment for prostate cancer. Heterogeneity across model inputs yields variable conclusions with respect to the favorability and cost-effectiveness of treatment options. Decision makers are cautioned to review estimates in CEAs to ensure they are up to date and relevant to setting and population.

Hyperfractionated-Accelerated Reirradiation with Proton Therapy for Radiation-Associated Breast Angiosarcoma

Purpose

Radiation-associated angiosarcoma (RAAS) is a rare complication among patients treated with radiation therapy for breast cancer. Hyperfractionated-accelerated reirradiation (HART) improves local control after surgery. Proton therapy may further improve the therapeutic ratio by mitigating potential toxicity.

Materials and Methods

Six patients enrolled in a prospective registry with localized RAAS received HART with proton therapy between 2015 and 2021. HART was delivered twice or thrice daily in fraction sizes of 1.5 or 1.0 Gy, respectively. All patients received 45 Gy to a large elective volume followed by boosts to a median dose of 65 (range, 60-75) Gy. Toxicity was recorded prospectively by using the Common Terminology Criteria for Adverse Events, version 4.0.

Results

The median follow-up duration was 1.5 (range, 0.25-2.9) years. The median age at RAAS diagnosis was 73 (range, 60-83) years with a median latency of 8.9 (range, 5-14) years between radiation therapy completion and RAAS diagnosis. The median mean heart dose was 2.2 (range, 0.1-4.96) Gy. HART was delivered postoperatively (n = 1), preoperatively (n = 3), preoperatively for local recurrence after initial management with mastectomy (n = 1), and as definitive treatment (n = 1). All patients had local control of disease throughout follow-up. Three of 4 patients treated preoperatively had a pathologic complete response. The patient treated definitively had a complete metabolic response on her posttreatment PET/CT (positron emission tomography–computed tomography) scan. Two patients developed distant metastatic disease despite local control and died of their disease. Acute grade 3 toxicity occurred in 3 patients: 2 patients undergoing preoperative HART experienced wound dehiscence and 1 postoperatively developed grade 3 wound infection, which resolved.

Conclusion

HART with proton therapy appears effective for local control of RAAS with a high rate of pathologic complete response and no local recurrences to date. However, vigilant surveillance for distant metastasis should occur. Toxicity is comparable to that in photon/electron series. Proton therapy for RAAS may maximize normal tissue sparing in this large-volume reirradiation setting.

Modern Therapy for Spinal and Paraspinal Ewing Sarcoma: An Update of the XXX Experience

PURPOSE

In 2010, we published a comprehensive review of our institutional outcomes treating children with spinal and paraspinal Ewing sarcoma using photon therapy. Multimodality therapy was associated with fair disease control but also with serious toxicity, including a 37% rate of Grade ≥3 toxicity. We therefore sought to assess our more recent experience treating children with more modern technology and treatment regimens.

METHODS AND MATERIALS

Between 2010 and 2021, 32 pediatric patients with nonmetastatic spinal and paraspinal Ewing sarcoma were treated at XXX and enrolled in a retrospective outcome study. Median age at diagnosis was 9.8 (range, 2.1-21.8) years old. Three, 22, and 7 tumors arose within the cervical, thoracic, and lumbar spine regions, respectively. Median maximum tumor diameter was 5 (range, 3-19) cm. At diagnosis, 28/32 patients had motor, bowel, or bladder deficits. Chemotherapy was delivered per contemporary North American and European interval-compressed regimens. Before radiotherapy, 14 patients underwent gross total resection while 18 underwent a biopsy or subtotal resection with cord decompression. All patients were treated with proton therapy; 6 with hardware stabilization also received a component of intensity-modulated photon therapy. Median prescription dose was 50.4 (range, 45-54) GyRBE. Median maximum dose to the spinal cord was 50.2 (range, 0-54.9) GyRBE.

RESULTS

With a median follow-up of 4.1 (range, 0.7 - 9.4) years, the 5-year local control, progression-free survival, and overall survival rates were 92%, 79%, and 85%, respectively. Ten of 30 living patients have residual motor, bowel, or bladder deficits. Overall, 22% of patients experienced CTCAE grade 3 late toxicity related to multimodality treatment: kyphosis (n=4), esophagitis (n=2) and chronic kidney disease (n=1). No patients developed grade ≥4 toxicity, new neurologic deficits, or second malignancy.

CONCLUSION

Modern treatment advances may offer an improved therapeutic ratio for pediatric spinal and paraspinal Ewing sarcoma. With appropriate management, most patients can be cured with recovery of long-term neurologic function and modest side-effects.

Pulmonary dose tolerance in hemithorax radiotherapy for Ewing sarcoma of the chest wall: Are we overestimating the risk of radiation pneumonitis?

BACKGROUND

Children with chest wall Ewing sarcoma with malignant pulmonary effusion or pleural stranding require hemithorax radiation, often with plans that exceed lung constraints. We investigated disease control and pneumonitis in children requiring hemithorax radiation.

PROCEDURE

Eleven children (median age 13 years) received hemithorax radiotherapy. Symptomatic radiation pneumonitis was considered National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) grade 1+ with respiratory symptoms. Mean lung dose (MLD), volume of lung exposed to a dose ≥5 Gy (V5), ≥20 Gy (V20), and ≥35 Gy (V35) were recorded. Adult and pediatric lung constraints were obtained from Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) guidelines and Children's Oncology Group (COG) protocols, respectively.

RESULTS

Median hemithorax dose was 15 Gy (1.5 Gy/fraction). Median total dose was 51 Gy (1.8 Gy/fraction). Most plans delivered both protons and photons. The ipsilateral MLD, V5, and V20 were 27.2 Gy, 100%, and 48.3%; the bilateral MLD, V20, and V35 were 14.1 Gy, 22.8%, and 14.3%, respectively. One hundred percent, 36%, and 91% of treatments exceeded recommended adult ipsilateral lung constraints of V5 <65%, V20 <52%, and MLD of 22 Gy; 64%, 45%, and 82% exceeded COG bilateral lung constraints of V20 <20%, MLD <15 Gy, and MLD <12 Gy, respectively; 82% of treatments exceeded the COG ipsilateral lung constraint of V20 <30%. At a median 36 months (range 12-129), the symptomatic radiation pneumonitis incidence was 0%. Two patients progressed with nonpulmonary metastatic disease and died at a median 12 months following radiotherapy.

CONCLUSIONS

Existing guidelines may overestimate pneumonitis risk, even among young children receiving multiagent chemotherapy. For children with chest wall Ewing sarcoma and other thoracic malignancies, more data are needed to refine pediatric dose-effect models for pulmonary toxicity.

Pericardial Effusion during Proton Therapy in a Patient with Chemorefractory Hodgkin Lymphoma

We present a case of recurrent pericardial effusion presenting during proton therapy in a 24-year-old female receiving mediastinal treatment for classical Hodgkin lymphoma. Pericardial effusion is typically considered an event accompanying lymphoma diagnosis or as a subacute or late effect of radiotherapy. Rarely has it been described as occurring during radiation treatment with photon-based radiotherapy, let alone proton therapy. It is unclear what underlying cause triggered recurrent effusion in this patient. Identifying and managing pericardial effusion during treatment delivery is important to consider as it may affect radiation dosimetry, particularly with proton therapy. Doing so will help ensure patients receive optimal treatment and minimize the risks of morbidity and mortality.

Proton Therapy for Breast Cancer: A Consensus Statement From the Particle Therapy Cooperative Group Breast Cancer Subcommittee

Radiation therapy plays an important role in the multidisciplinary management of breast cancer. Recent years have seen improvements in breast cancer survival and a greater appreciation of potential long-term morbidity associated with the dose and volume of irradiated organs. Proton therapy reduces the dose to nontarget structures while optimizing target coverage. However, there remain additional financial costs associated with proton therapy, despite reductions over time, and studies have yet to demonstrate that protons improve upon the treatment outcomes achieved with photon radiation therapy. There remains considerable heterogeneity in proton patient selection and techniques, and the rapid technological advances in the field have the potential to affect evidence evaluation, given the long latency period for breast cancer radiation therapy recurrence and late effects. In this consensus statement, we assess the data available to the radiation oncology community of proton therapy for breast cancer, provide expert consensus recommendations on indications and technique, and highlight ongoing trials' cost-effectiveness analyses and key areas for future research.

Bicentric Treatment Outcomes After Proton Therapy for Nonmyxopapillary High-Grade Spinal Cord Ependymoma in Children

PURPOSE

Few studies report outcomes in children treated with radiation for nonmyxopapillary ependymoma of the spinal cord, and little evidence exists to inform decisions regarding target volume and prescription dose. Moreover, virtually no mature outcome data exist on proton therapy for this tumor. We describe our combined institutional experience treating pediatric classical/anaplastic ependymoma of the spinal cord with proton therapy.

METHODS AND MATERIALS

Between 2008 and 2019, 14 pediatric patients with nonmetastatic nonmyxopapillary grade II (n = 6) and grade III (n = 8) spinal ependymoma received proton therapy. The median age at radiation was 14 years (range, 1.5-18 years). Five tumors arose within the cervical cord, 3 within the thoracic cord, and 6 within the lumbosacral cord. Before radiation therapy, 3 patients underwent subtotal resection, and 11 underwent gross-total or near total resection. Two patients received chemotherapy. For radiation, the clinical target volume received 50.4 Gy (n = 8), 52.2 (n = 1), or 54 Gy (n = 5), with the latter receiving a boost to the gross tumor volume after the initial 50.4 Gy, modified to respect spinal cord tolerance.

RESULTS

With a median follow-up of 6.3 years (range, 1.5-14.8 years), no tumors progressed. Although most patients experienced neurologic sequela after surgery, only 1 developed additional neurologic deficits after radiation: An 18-year-old male who received 54 Gy after gross total resection of a lumbosacral tumor developed grade 2 erectile dysfunction. There were 2 cases of musculoskeletal toxicity attributable to surgery and radiation. At analysis, no patient had developed cardiac, pulmonary, or other visceral organ complications or a second malignancy.

CONCLUSION

Radiation to a total dose of 50 to 54 Gy can be safely delivered and plays a beneficial role in the multidisciplinary management of children with nonmyxopapillary spinal cord ependymoma. Proton therapy may reduce late radiation effects and is not associated with unexpected spinal cord toxicity.

Establishing cost-effective allocation of proton therapy for patients with mediastinal Hodgkin lymphoma

PURPOSE

For curative treatment of Hodgkin lymphoma, radiotherapy benefit must be weighed against toxicity. Although more costly, proton radiotherapy reduces dose to healthy tissue, potentially improving the therapeutic ratio compared to photons. We sought to determine the cost-effectiveness of proton versus photon therapy for mediastinal Hodgkin lymphoma (MHL) based on reduced heart disease.

METHODS

Our model approach was two-fold: (1) Utilize patient-level dosimetric information for a cost-effectiveness analysis using a Markov cohort model. (2) Utilize population-based data to develop guidelines for policy-makers to determine thresholds of proton therapy favorability for a given photon dose. The HD14 trial informed relapse risk; coronary heart disease risk was informed by the Framingham risk calculator modified by the mean heart dose (MHD) from radiation. Sensitivity analyses assessed model robustness and identified the most influential model assumptions. A 30-year-old adult with MHL was the base case using 30.6-Gy proton therapy versus photon intensity-modulated radiotherapy.

RESULTS

Proton therapy was not cost-effective in the base case for male ($129K/QALY) or female patients ($196/QALY). A 5-Gy MHD decrease was associated with proton therapy incremental cost-effectiveness ratio<$100K/QALY in 40% of scenarios. The hazard ratio associating MHD and heart disease was the most influential clinical parameter.

CONCLUSION

Proton therapy may be cost-effective a select minority of patients with MHLbased on age, sex, and MHD reduction. We present guidance for clinicians utilizing MHD to aid decision-making for radiotherapy modality.

Comparative Effectiveness of Proton Therapy versus Photon Radiotherapy in Adolescents and Young Adults for Classical Hodgkin Lymphoma

Purpose

Early stage (stages I-II) classical Hodgkin lymphoma (cHL) is a highly curable disease typically diagnosed in adolescents and young adults (AYAs). Proton therapy can also reduce the late toxicity burden in this population, but data on its comparative efficacy with photon radiotherapy in this population are sparse. We assessed outcomes in AYAs with cHL in a multi-institution retrospective review.

Materials and Methods

We identified 94 patients aged 15 to 40 years with stages I and II cHL treated with radiotherapy as part of their initial treatment between 2008 and 2017. We used Kaplan-Meier analyses and log-rank testing to evaluate survival differences between groups of patients.

Results

A total of 91 patients were included in the analysis. The 2-year progression-free survival (PFS) rate was 89%. Of the 12 patients who experienced progression after radiotherapy, 4 occurred out-of-field, 2 occurred in-field, and 6 experienced both in- and out-of-field progression. There was no significant difference in 2-year PFS among AYA patients by radiotherapy dose received (≥ 30 Gy, 91%; < 30 Gy, 86%; P = .82). Likewise, there was no difference in 2-year PFS among patients who received either proton or photon radiotherapy (proton, 94%; photon, 83%; P = .07).

Conclusion

Our cohort of AYA patients had comparable outcomes regardless of radiotherapy dose or modality used. For patients with significant risk of radiation-induced late effects, proton therapy is a reasonable treatment modality.

Second tumor risk in children treated with proton therapy

BACKGROUND

Out-of-field neutron dissemination during double-scattered proton therapy has raised concerns of increased second malignancies, disproportionally affecting pediatric patients due to the proportion of body exposed to scatter dose and inherent radiosensitivity of developing tissue. We sought to provide empiric data on the incidence of early second tumors.

METHODS

Between 2006 and 2019, 1713 consecutive children underwent double-scattered proton therapy. Median age at treatment was 9.1 years; 371 were ≤3 years old. Thirty-seven patients (2.2%) had tumor predisposition syndromes. Median prescription dose was 54 Gy (range 15-75.6). Median follow-up was 3.3 years (range 0.1-12.8), including 6587 total person-years. Five hundred forty-nine patients had ≥5 years of follow-up. A second tumor was defined as any solid neoplasm throughout the body.

RESULTS

Eleven patients developed second tumors; the 5- and 10-year cumulative incidences were 0.8% (95% CI, 0.4-1.9%) and 3.1% (95% CI, 1.5-6.2%), respectively. Using age- and gender-specific data from the Surveillance, Epidemiology, and End Results (SEER) program, the standardized incidence ratio was 13.5; the absolute excess risk was 1.5/1000 person-years. All but one patient who developed second tumors were irradiated at ≤5 years old (p < .0005). There was also a statistically significant correlation between patients with tumor predisposition syndromes and second tumors (p < .0001). Excluding patients with tumor predisposition syndromes, 5- and 10-year rates were 0.6% (95% CI, 0.2-1.7%) and 1.7% (95% CI, 0.7-4.0%), respectively, with all five malignant second tumors occurring in the high-dose region.

CONCLUSION

Second tumors are rare within the decade following double-scattered proton therapy, particularly among children irradiated at >5 years old and those without tumor predisposition syndrome.

Local Control After Proton Therapy for Pediatric Chordoma

PURPOSE

Due to the location and high dose required for disease control, pediatric chordomas are theoretically well-suited for treatment with proton therapy, but their low incidence limits the clinical outcome data available in the literature. We sought to report the efficacy and toxicity of proton therapy among a single-institution cohort.

METHODS AND MATERIALS

Between 2008 and 2019, 29 patients with a median age of 14.8 years (range, 3.8-21.8) received passive-scattered proton therapy for nonmetastatic chordoma. No patient received prior irradiation. Twenty-four tumors arose in the clivus/cervical spine region and 5 in the lumbosacral spine. Twenty-six tumors demonstrated classic well-differentiated histology and 3 were dedifferentiated or not otherwise specified. Approximately half of the tumors underwent specialized testing: 14 were brachyury-positive and 10 retained INI-1. Three patients had locally recurrent tumors after surgery alone (n = 2) or surgery + chemotherapy (n = 1), and 17 patients had gross disease at the time of radiation. The median radiation dose was 73.8 Gy relative biological effectivness (range, 69-75.6).

RESULTS

With a median follow-up of 4.3 years (range, 1.0-10.7), the 5-year estimates of local control, progression-free survival, and overall survival rates were 85%, 82%, and 86%, respectively. No disease progression was observed beyond 3 years. Excluding 3 patients with dedifferentiated/not-otherwise-specified chordoma, the 5-year local control, progression-free survival, and overall survival rates were 92%, 92%, and 91%, respectively. Serious toxicities included 3 patients with hardware failure or related infection requiring revision surgery, 2 patients with hormone deficiency, and 2 patients with Eustachian tube dysfunction causing chronic otitis media. No patient experienced brain stem injury, myelopathy, vision loss, or hearing loss after radiation.

CONCLUSIONS

In pediatric patients with chordoma, proton therapy is associated with a low risk of serious toxicity and high efficacy, particularly in well-differentiated tumors. Complete resection may be unnecessary for local control, and destabilizing operations requiring instrumentation may result in additional complications after therapy.

Outcomes following limited-volume proton therapy for multifocal spinal myxopapillary ependymoma

PURPOSE

Spinal myxopapillary ependymoma (MPE) often presents with a multifocal distribution, complicating attempts at resection. There remains no standard approach to irradiating these patients. We report disease control and toxicity in pediatric patients with multifocal spinal MPE treated with limited-volume proton therapy.

MATERIALS/METHODS

Twelve patients (≤21 years old) with multifocal spinal MPE were treated between 2009 and 2018 with limited-volume brain-sparing proton therapy. Median age was 13.5 years (range, 7-21). Radiotherapy was given as adjuvant therapy after primary surgery in five patients (42%) and for recurrence in seven (58%). No patient received prior radiation. Eleven patients (92%) had evidence of gross disease at radiotherapy. Eleven patients received 54 GyRBE; one received 50.4 GyRBE. Treatment toxicity was graded per the CTCAEv4.0. We estimated disease control and survival using the Kaplan-Meier product-limit method.

RESULTS

The median follow-up was 3.6 years (range, 1.8-10.6). The five-year actuarial rates of local control, progression-free survival, and overall survival were 100%, 92%, and 100%, respectively. One patient experienced an out-of-field recurrence in the spine superior to the irradiated region. No patients developed in-field recurrences. Following surgery and irradiation, one patient developed grade three spinal kyphosis and one patient developed grade 2 unilateral L5 neuropathy.

CONCLUSION

54 GyRBE to a limited volume appears effective for disseminated spinal MPE in both the primary and salvage settings, sparing children the toxicity of full craniospinal irradiation. Compared with historical reports, this approach using proton therapy improves the therapeutic ratio, resulting in minimal side effects and high rates of disease control.

Incorporation of the LETd-weighted biological dose in the evaluation of breast intensity-modulated proton therapy plans

PURPOSE

To evaluate the LETd-weighted biological dose to OARs in proton therapy for breast cancer and to study the relationship of the LETd-weighted biological dose relative to the standard dose (RBE = 1.1) and thereby to provide estimations of the biological dose uncertainties with the standard dose calculations (RBE = 1.1) commonly used in clinical practice.

METHOD

This study included 20 patients who received IMPT treatment to the whole breast/chest wall and regional lymph nodes. The LETd distributions were calculated along with the physical dose using an open-source Monte Carlo simulation package, MCsquare. Using the McMahon linear model, the LETd-weighted biological dose was computed from the physical dose and LETd. OAR doses were compared between the Dose (RBE = 1.1) and the LETd-weighted biological dose, on brachial plexus, rib, heart, esophagus, and Ipsilateral lung.

RESULTS

On average, the LETd-weighted biological dose compared to the Dose (RBE = 1.1) was higher by 8% for the brachial plexus D0.1 cc, 13% for the ribs D0.5 cc, 24% for mean heart dose, and 10% for the esophagus D0.1 cc, respectively. The LETd-weighted doses to the Ipsilateral lung V5, V10, and V20 were comparable to the Dose (RBE = 1.1). No statistically significant difference in biological dose enhancement to OARs was observed between the intact breast group and the CW group, with the exception of the ribs: the CW group experienced slightly greater biological dose enhancement (13% vs. 12%, p = 0.04) to the ribs than the intact breast group.

CONCLUSION

Enhanced biological dose was observed compared to standard dose with assumed RBE of 1.1 for the heart, ribs, esophagus, and brachial plexus in breast/CW and regional nodal IMPT plans. Variable RBE models should be considered in the evaluation of the IMPT breast plans, especially for OARs located near the end of range of a proton beam. Clinical outcome studies are needed to validate model predictions for clinical toxicities.

Cross-Sectional International Survey to Determine the Educational Interests of Spanish-Speaking Latin American Radiation Oncologists

PURPOSE

With the existing oncology disparities in Latin America, physician expertise has been cited as a possible contributor to inferior oncologic outcomes in some cancers. As two-dimensional radiotherapy rapidly evolved to intensity-modulated radiation therapy in Latin America, adequate contouring education is an actionable target to improving physician knowledge and clinical outcomes. Yet, topics of interest to Latin American radiation oncologists are underreported. We assessed Latin American interest in a virtual platform for case discussion and identified the educational topics of most interest to them.

MATERIALS AND METHODS

A Spanish-language online survey was designed by a team of Latin American educators. The questions assessed professional nationality, desire for an online educational platform for case presentation, career length, and topics of interest. Educational topics included head and neck (H&N), CNS, GI, lung, gynecologic, breast, and pediatric cancers, lymphoma, sarcoma, stereotactic body radiotherapy (SBRT), brachytherapy, and medical physics.

RESULTS

One hundred thirty-three surveys were included for analysis. Overall, 127 respondents (98%) affirmed interest in participating in a virtual platform for case discussion and treatment advances. The most popular educational themes were H&N cancers (24%), SBRT (14%), and CNS cancers (13%). Of countries with > 10 respondents, the most popular educational topic remained H&N cancers for Argentina, Chile, and Mexico, but the most popular topic among Peruvian respondents was CNS cancer (27%).

CONCLUSION

With international collaboration and a large sample size, we present the first survey results describing Latin American radiation oncology educational interests. Participants were overwhelmingly interested in a virtual platform, and most were specifically interested in H&N cancer education. These results can be used for focused didactic preparation in Latin America. Future efforts should expand on improving representation and outreach among Central American radiation oncologists.

Risk of Pneumonitis and Outcomes After Mediastinal Proton Therapy for Relapsed/Refractory Lymphoma: A PTCOG and PCG Collaboration

PURPOSE

Despite high response rates, there has been reluctance to use radiation therapy for patients with relapsed/refractory (r/r) Hodgkin (HL) or aggressive non-Hodgkin lymphoma (NHL) given concerns for subacute and late toxicities. Symptomatic pneumonitis, a subacute toxicity, has an incidence of 17% to 24% (≥grade 2) even with intensity modulated radiation therapy. Proton therapy (PT), which has no exit radiation dose, is associated with a lower dose to lung compared with other radiation techniques. As risk of radiation pneumonitis is associated with lung dose, we evaluated whether pneumonitis rates are lower with PT.

METHODS AND MATERIALS

Within an international, multi-institutional cohort, we retrospectively evaluated the incidence and grade of radiation pneumonitis (National Cancer Institute Common Terminology Criteria for Adverse Events v4) among patients with r/r HL or NHL treated with PT.

RESULTS

A total of 85 patients with r/r lymphoma (66% HL, 34% NHL; 46% primary chemorefractory) received thoracic PT from 2009 to 2017 in the consolidation (45%) or salvage (54%) setting. Median dose was 36 Gy(RBE). Before PT, patients underwent a median of 1 salvage systemic therapy (range, 0-4); 40% received PT within 4 months of transplant. With a median follow-up of 26.3 months among living patients, 11 patients developed symptomatic (grade 2) pneumonitis (12.8%). No grade 3 or higher pneumonitis was observed. Dose to lung, including mean lung dose, lung V5, and V20, significantly predicted risk of symptomatic pneumonitis, but not receipt of brentuximab, history of bleomycin toxicity, sex, or peritransplant radiation.

CONCLUSIONS

PT for relapsed/refractory lymphoma was associated with favorable rates of pneumonitis compared with historical controls. We confirm that among patients treated with PT, pneumonitis risk is associated with mean lung and lung V20 dose. These findings highlight how advancements in radiation delivery may improve the therapeutic ratio for patients with relapsed/refractory lymphoma. PT may be considered as a treatment modality for patients with relapsed/refractory lymphoma in the consolidation or salvage setting.

Patient-specific quality assurance and plan dose errors on breast intensity-modulated proton therapy

PURPOSE

To investigate, in proton therapy, whether the Gamma passing rate (GPR) is related to the patient dose error and whether MU scaling can improve dose accuracy.

METHODS

Among 20 consecutively treated breast patients selected for analysis, two IMPT plans were retrospectively generated: (1) the pencil-beam (PB) plan and (2) the Monte Carlo (MC) plan. Patient-specific QA was performed. A 3%/3-mm Gamma analysis was conducted to compare the TPS-calculated PB algorithm dose distribution with the measured 2D dose. Dose errors were compared between the plans that passed the Gamma testing and those that failed. The MU was then scaled to obtain a better GPR. MU-scaled PB plan dose errors were compared to the original PB plan.

RESULTS

Of the 20 PB plans, 8 were passed Gamma testing (G_pass_group) and 12 failed (G_fail_group). Surprisingly, the G_pass_group had a greater dose error than the G_fail_group. The median (range) of the PTV DVH RMSE and PTV ΔDmean were 1.36 (1.00-1.91) Gy vs 1.18 (1.02-1.80) Gy and 1.23 (0.92-1.71) Gy vs 1.10 (0.87-1.49) Gy for the G_pass_group and the G_fail_group, respectively. MU scaling reduced overall dose error. However, for PTV D99 and D95, MU scaling worsened some cases.

CONCLUSION

For breast IMPT, the PB plans that passed the Gamma testing did not show smaller dose errors compared to the plans that failed. For individual plans, the MU scaling technique leads to overall smaller dose errors. However, we do not suggest use of the MU scaling technique to replace the MC plans when the MC algorithm is available.

Irradiating Residual Disease to 30 Gy with Proton Therapy in Pediatric Mediastinal Hodgkin Lymphoma

Background:

Local relapse is a predominant form of recurrence among pediatric patients with Hodgkin lymphoma (PHL). Although PHL radiotherapy doses have been approximately 20 Gy, adults with Hodgkin lymphoma receiving 30 to 36 Gy experience fewer in-field relapses. We investigated the dosimetric effect of such a dose escalation to the organs at risk (OARs).

Materials and Methods:

Ten patients with PHL treated with proton therapy to 21 Gy involved-site radiation therapy (ISRT_21Gy) were replanned to deliver 30 Gy by treating the ISRT to 30 Gy (ISRT_30Gy), delivering 21 Gy to the ISRT plus a 9-Gy boost to postchemotherapy residual volume (rISRT_boost), and delivering 30 Gy to the residual ISRT target only (rISRT_30Gy). Radiation doses to the OARs were compared.

Results:

The ISRT_30Gy escalated the dose to the target by 42% but also to the OARs. The rISRT_boost escalated the residual target dose by 42%, and the OAR dose by only 17% to 26%. The rISRT_30Gy escalated the residual target dose by 42% but reduced the OAR dose by 25% to 46%.

Conclusion:

Boosting the postchemotherapy residual target dose to 30Gy can allow for dose escalation with a slight OAR dose increase. Treating the residual disease for the full 30Gy, however, would reduce the OAR dose significantly compared with ISRT_21Gy. Studies should evaluate these strategies to improve outcomes and minimize the late effects.

Pathways for Recruiting and Retaining Women and Underrepresented Minority Clinicians and Physician Scientists Into the Radiation Oncology Workforce: A Summary of the 2019 ASTRO/NCI Diversity Symposium Session at the ASTRO Annual Meeting

Diversifying the radiation oncology workforce is an urgent and unmet need. During the American Society of Radiation Oncology (ASTRO) 2019 Annual Meeting, ASTRO's Committee on Health Equity, Diversity, and Inclusion (CHEDI) and the National Cancer Institute (NCI) collaborated on the ASTRO-NCI Diversity Symposium, entitled "Pathways for Recruiting and Retaining Women and Underrepresented Minority Clinicians and Physician Scientists Into the Radiation Oncology Workforce." Herein, we summarize the presented data and personal anecdotes with the goal of raising awareness of ongoing and future initiatives to improve recruitment and retention of underrepesented groups to radiation oncology. Common themes include the pivotal role of mentorship and standardized institutional practices – such as protected time and pay parity – as critical to achieving a more diverse and inclusive workplace.

Treatment Outcomes After Proton Therapy for Ewing Sarcoma of the Pelvis

PURPOSE

Ewing sarcoma of the pelvis is associated with inferior local control compared with those arising from other primary sites. Despite its increased use, outcome data for treatment with proton therapy remain limited. We report 3-year disease control and toxicity in pediatric patients treated with proton therapy.

METHODS AND MATERIALS

Thirty-five patients aged ≤21 years (median, 14 years) with nonmetastatic pelvic Ewing sarcoma received proton therapy and chemotherapy between 2010 and 2018. Overall survival and tumor control rates were calculated using the Kaplan-Meier method. A log-rank test assessed significance between strata of prognostic factors. Significant toxicity was reported per the Common Terminology Criteria for Adverse Events, version 4.0.

RESULTS

Most patients received definitive radiation (n = 26; median dose 55.8 Gy relative biological effectiveness [RBE]; range, 54.0-64.8), 7 received preoperative radiation (50.4 Gy RBE), and 2 received postoperative radiation (45 Gy RBE and 54 Gy RBE). The median primary tumor size was 10.5 cm. With a median follow-up of 3 years (range, 0.3-9.0 years), the 3-year overall survival, progression-free survival, and local control rates were 83% (95% confidence interval [CI], 65%-93%), 64% (95% CI, 45%-79%), and 92% (95% CI, 74%-98%), respectively. There was no association between local control, progression-free survival, or overall survival and tumor size, patient age, radiation dose, or definitive versus pre-/postoperative radiation therapy. Median time to progression was 1 year (range, 0.1-1.9 years). All patients with large tumors (≥8 cm) who underwent definitive proton therapy with a higher dose (≥59.4 Gy RBE) remained free from tumor recurrence (n = 5). Five patients experienced grade ≥2 subacute/late toxicity, all of whom were treated with combined surgery and radiation.

CONCLUSIONS

Definitive proton therapy offers local control comparable to photon therapy in pediatric patients with pelvic Ewing sarcoma. These data lend preliminary support to radiation dose escalation without significant toxicity, which may contribute to the favorable outcomes. Combined surgery and radiation therapy, particularly preoperative radiation, is associated with postoperative complications, but not survival, compared with radiation alone.

Dosimetric consequences of image guidance techniques on robust optimized intensity-modulated proton therapy for treatment of breast Cancer

PURPOSE

To investigate the consequences of residual setup error on target dose distribution using various image registration strategies for breast cancer treated with intensity-modulated proton therapy (IMPT).

MATERIALS AND METHODS

Among 11 post-lumpectomy patients who received IMPT, 44 dose distributions were computed. For each patient, the original plan (Plan-O) and three verification plans were calculated using different alignments: bony anatomy (VPlan-B), breast tissue (VPlan-T), and skin (VPlan-S). The target coverage were evaluated for each alignment technique. Additionally, 2 subvolumes-BreastNearSkin (1-cm rim of anterior CTV) and BreastNearCW (1-cm rim of posterior CTV)-were created to help localize CTV underdosing. Furthermore, we divided the setup error into the posture error and breast error. Patients with a large posture error and those with good posture setup but a large breast error were identified to evaluate the effect of posture error and breast error.

RESULTS

For Plan-O, VPlan-B, VPlan-T, and VPlan-S, respectively, the median (interquartile range) breast CTV D95 was 95.7%(94.7-96.3%), 95.1% (93.9-95.7%), 95.2% (94.8-95.6%), and 95.2% (94.9-95.7%); BreastNearCW D95 was 96.9% (95.6-97.3%), 94.8% (93.5-97.0%), 95.6% (94.8-97.0%), 95.6% (94.8-97.1%); and BreastNearSkin D95 was 94.1% (92.7-94.4%), 93.6% (92.2-94.5%), 93.5% (92.4-94.5%), and 94.4% (92.2-94.5%) of the prescription dose. 4/11 patients had ≥1% decrease in breast CTV D95, 1 of whom developed breast edema while the other 3 all had a > 2^o posture error. The CTV D95 variation was within 1% for the patients with good posture setup but >2^o breast error.

CONCLUSION

Acceptable target coverage was achieved with all three alignment strategies. Breast tissue and skin alignment maintained the breast target coverage marginally better than bony alignment, with which the posterior CTV along the chest wall is the predominant area affected by under-dosing. For target dose distribution, posture error appears more influential than breast error.

Outcomes following proton therapy for Ewing sarcoma of the cranium and skull base

PURPOSE

Despite the dosimetric advantages of proton therapy, little data exist on patients who receive proton therapy for Ewing sarcoma of the cranium and skull base. This study reports local disease control and toxicity in such patients.

MATERIALS/METHODS

We reviewed 25 patients (≤21 years old) with nonmetastatic Ewing sarcoma of the cranium and skull base treated between 2008 and 2018. Treatment toxicity was graded per the Common Terminology Criteria for Adverse Events v4.0. The Kaplan-Meier product limit method provided estimates of disease control and survival.

RESULTS

Median patient age was 5.9 years (range, 1-21.7). Tumor subsites included the skull base (48%), non-skull-base calvarial bones (28%), paranasal sinuses (20%), and nasal cavity (4%). All patients underwent multiagent alkylator- and anthracycline-based chemotherapy; 16% underwent gross total resection (GTR) before radiation. Clinical target volume (CTV) 1 received 45 GyRBE and CTV2 received 50.4 GyRBE following GTR or 54-55.8 GyRBE following biopsy or subtotal resection. Median follow-up was 3.7 years (range, 0.26-8.3); no patients were lost. The 4-year local control, disease-free survival, and overall survival rates were 96%, 86%, and 92%, respectively. Two patients experienced in-field recurrences. One patient experienced bilateral conductive hearing loss requiring aids, two patients developed intracranial vasculopathy, and 6 patients required hormone replacement therapy for neuroendocrine deficits. None developed a secondary malignancy.

CONCLUSION

Proton therapy is associated with a favorable therapeutic ratio in children with large Ewing tumors of the cranium and skull base. Despite its high conformality, we observed excellent local control and no marginal recurrences. Treatment dosimetry predicts limited long-term neurocognitive and neuroendocrine side effects.

Using Robust Optimization for Skin Flashing in Intensity Modulated Radiation Therapy for Breast Cancer Treatment: A Feasibility Study

PURPOSE

To study the feasibility and the effectiveness of a novel implementation of robust optimization on 2 sets of computed tomography (CT) data simultaneously for skin flashing in intensity modulated radiation therapy for breast cancer.

METHOD AND MATERIALS

Five patients who received treatment to the breast and regional lymphatics were selected for this study. For each patient, 3 plans were generated using 3 different skin-flashing methods, including (1) a manual flash plan with optimization on the nominal planning target volume (PTV) not extending beyond the skin that required manually postplanning the opening of the multi-leaf collimator and jaw to obtain flash; (2) an expanded PTV plan with optimization on an expanded PTV that included the target in the air beyond the skin; and (3) a robust-optimized (RO) plan using robust optimization that simultaneously optimizes on the nominal CT data set and a simulated geometry error CT data set. The feasibility and the effectiveness of the robust optimization approach was investigated by comparing it with the 2 other methods. The robustness of the plan against target position variations was studied by simulating 0-, 5-, 10-, and 15-mm geometry errors.

RESULTS

The RO plans were the only ones able to meet acceptable criteria for all patients in both the nominal and simulated geometry error scenarios. The expanded PTV plans developed major deviation on the maximum dose to the PTV for 1 patient. For the manual flash plans, every patient developed major deviation either on 95% of the dose to the PTV or the maximum dose to the PTV in the simulated geometry error scenarios. The RO plan demonstrated the best robustness against the target position variation among the 3 methods of skin flashing. The doses to the lung and heart were comparable for all 3 planning techniques.

CONCLUSION

Using robust optimization for skin flash in breast intensity modulated radiation therapy planning is feasible. Further investigation is warranted to confirm the clinical effectiveness of this novel approach.

Novel Pilot Curriculum for International Education of Lymphoma Management Using E-Contouring

PURPOSE

The International Lymphoma Radiation Oncology Group (ILROG) published consensus guidelines on the management of Hodgkin disease (HD) and nodal non-Hodgkin lymphoma (NHL), which became the most downloaded articles from International Journal of Radiation Oncology, Biology, and Physics. E-contouring workshops allow for interactive didactic sessions, allowing participants to see case-based contouring in real time. A pilot 1-hour curriculum was developed with the objective of reviewing ILROG guidelines for HD and NHL management with incorporation of e-contouring tools. This represents the first international education intervention in Spanish using e-contouring with a pre- and postintervention questionnaire.

METHODS

A 1-hour presentation was prepared in Spanish reviewing the ILROG recommendations for HD and NHL. The review was followed by the author's demonstration of contour creation using patients with HD and NHL prepared for the American Society for Radiation Oncology's 2015 e-contouring lymphoma session. A five- question evaluation was prepared and administered before and after intervention. A two-tailed paired t test was performed to evaluate any significant change in test value before and after intervention.

RESULTS

A total of nine quizzes were collected before and after the intervention. The average test score before the intervention was 75.6%, and the average test score after the intervention was 86.7% ( P = .051). Four students scored 100% on both the pre- and postintervention evaluations, and no student had a decrease in score from pre- to postintervention evaluation. The topic with the lowest score tested dose consideration.

CONCLUSION

A substantial but nonsignificant improvement in test evaluation was seen with this pilot curriculum. This pilot intervention identified obstacles for truly interactive didactic sessions that, when addressed, can lead to fully developed interactive didactic sessions.

Insurance Coverage for Adjuvant Proton Therapy in the Definitive Treatment of Breast Cancer

Purpose

To determine factors that influence insurance approval for breast cancer patients for whom adjuvant proton therapy (PT) is recommended.

Patients and Methods

We sought to identify factors associated with PT approval among 131 insured patients seen in consultation between 2014 and 2018 and recommended adjuvant PT. Insurance status included: commercial, 76 patients (58%); Medicare, 41 (31%); and Medicaid, 14 (11%). Ninety-six patients (73%) had policies that "covered" PT. Insurance "coverage" for PT was not associated with final approval nor was lack of "coverage" associated with denial despite additional steps of medical review, peer-to-peer discussion, patient appeal, and judicial review.In seeking approval, the following steps were required: medical review, 73 patients (56%); comparative dosimetry, 34 patients (26%); peer-to-peer discussion, 20 patients (15%); and administrative law judge, 1 patient (1%). A multivariate analysis of predictors for final insurance approval was conducted including the following covariates: T stage (Tis-T2 vs T3-T4); N stage (N0 vs N1-N3); laterality (left or bilateral vs right); insurance type (commercial vs Medicare/Medicaid) combined with potential insurance coverage (covered vs not covered); time period (2014-2016 vs 2017-2018); and age (<57 years vs 57 and older).

Results

Insurance approval was obtained for 93/96 patients (97%) with insurance that covered PT versus 23/35 patients (66%) whose insurance did not cover PT. Insurance approval stratified by insurance type and coverage was: commercial-covered, 52/52 patients (100%); Medicare or Medicaid-covered, 41/44 (93%); commercial-not covered, 16/22 (73%); and Medicare or Medicaid-not covered, 7/13 (54%).On multivariate analysis, factors impacting approval revealed T stage, p=0.3127; N stage, p=0.8524; laterality, p=0.1829; insurance type combined with potential coverage, p<0.0001; time period, p=0.2731; and age, p=0.6678.

Conclusion

The only parameter that significantly influenced approval for treatment with PT was insurance type combined with potential coverage with ultimate approval rates ranging from 54% to 100%.

45 GyRBE for group III orbital embryonal rhabdomyosarcoma

Purpose: Despite widespread concerns of radiotherapy toxicity in children with head and neck tumors, recent Children's Oncology Group (COG) findings suggest that the use of 45 Gy results in an unacceptably high rate of local recurrences in patients with low-risk orbital rhabdomyosarcoma. We therefore evaluated outcomes in our pediatric patients who received 45 GyRBE using proton therapy. Material and methods: To assess disease control and toxicity, we reviewed the medical records of 30 children (≤21 years old) with COG stage 1, group III embryonal orbital rhabdomyosarcoma enrolled on a prospective outcome study and treated with proton therapy between 2007 and 2018. Results: Median age at the time of radiation was 4.8 years old. Twenty-one and nine patients received ifosfamide- and cyclophosphamide-based chemotherapy according to their respective cooperative group regimens. Median duration between the start of induction chemotherapy and radiation was 12 weeks. Two patients had a complete response to induction chemotherapy and two had stable disease. Twenty-six patients had a partial response to induction chemotherapy, with a median volume reduction of 66%. With a median follow-up of 4.0 years (range, 0.5-9.5 years), we observed 1 local failure 6 months following treatment in a patient who had a partial response to cyclosphophomide-based induction chemotherapy. The 5-year local control, progression-free survival, and overall survival rates were 97%, 97%, and 100%, respectively. Serious late toxicities included 18 patients with cataracts, 4 with exposure keratoconjunctivitis resulting in permanently reduced visual acuity, and 1 with chronic sinusitis. Conclusion: 45 GyRBE offers effective local control for most patients with group III orbital rhabdomyosarcoma. The delivery of proton therapy to the postinduction tumor volume plus a small margin can mitigate early- and intermediate-term toxicity, but side effects still occur and long-term data are needed to demonstrate the dosimetric advantage of proton therapy.