Radiopharmaceuticals for Cancer Diagnosis and Therapy: New Targets, New Therapies-Alpha-Emitters, Novel Targets.

ABSTRACT: Radiopharmaceutical therapy has emerged as a promising approach for the treatment of various cancers. The exploration of novel targets such as tumor-specific antigens, overexpressed receptors, and intracellular biomolecules using antibodies, peptides, or small molecules has expanded the scope of radiopharmaceutical therapy, enabling precise and effective cancer treatment for an increasing number of tumor types. Alpha emitters, characterized by their high linear energy transfer and short path length, offer unique advantages in targeted therapy due to their potent cytotoxicity against cancer cells while sparing healthy tissues. This article reviews recent advancements in identifying novel targets for radiopharmaceutical therapy and applications in utilizing α-emitters for targeted treatment.

Factors Associated With and Characteristics of Patients Receiving Proton Therapy at the End of Life.

Purpose: To identify the characteristics, indications, and toxicities among patients receiving proton beam therapy (PBT) in the final year of life at an academic medical center. Materials and Methods: A retrospective review of patients who received PBT within the final 12 months of life was performed. Electronic medical records were reviewed for patient and treatment details from 2010 to 2019. Patients were followed from the start of PBT until death or last follow-up. Acute (3 months) toxicities were graded using the Common Terminology Criteria for Adverse Events v5.0. Imaging response was assessed using the Response Evaluation Criteria in Solid Tumors v1.1. The χ2 test was used to evaluate factors associated with palliative treatment. Simple logistic regression was used to evaluate factors associated with toxicity. Results: Bet299 patients were treated at the end of life (EOL) out of 5802 total patients treated with PBT (5.2%). Median age was 68 years (19-94 years), 58% male. The most common cancer was nonsmall cell lung cancer (27%). Patients were treated for symptom palliation alone (11%), durable control (57%), curative intent (16%), local recurrence (14%), or oligometastatic disease (2%). Forty-five percent received reirradiation. Median treatment time was 32 days (1-189 days). Acute toxicity was noted in 85% of the patients (31% G1, 53% G2, 15% G3). Thirteen patients (4%) experienced chronic toxicity. Breast and hematologic malignancy were associated with palliative intent χ2 (1, N = 14) = 17, P = .013; (χ2 (1, N = 14) = 18, P = .009). Conclusion: The number of patients treated with PBT at the EOL was low compared to all comers. Many of these patients received treatment with definitive doses and concurrent systemic therapy. Some patients spent a large portion of their remaining days on treatment. A prognostic indicator may better optimize patient selection for PBT at the EOL.

A systematic review of stage IVA cervical cancer treatment: Challenges in the management of an understudied group.

OBJECTIVE: Stage IVA patients comprise a small proportion of participants in cervical cancer trials, yet survival outcomes are disproportionately poor. We aim to perform a systematic review evaluating stage IVA cervical cancer. METHODS: This systematic review was completed via PRISMA 2020 guidelines using two databases. Inclusion criteria comprised Phase III trials (2004-2024) assessing stage IVA cervical cancer including patients by stage. Searches had MeSH terms: ((cervical cancer) AND (stage IVA) AND (locally advanced)). 761 were articles identified, including books, trials, reviews, and meta-analyses. Of the articles identified, 12 met inclusion criteria. RESULTS: A total of 133 (3.8% of study populations) stage IVA and 818 (40% of study populations) stage III-IVA cervical cancer patients were analyzed. Two studies (stage IVA n = 15; 3.1%) established cisplatin as chemoradiotherapy agent of choice, while one study (stage IVA n = 2; 1%) showed no benefit with cisplatin versus radiotherapy alone. Four studies (stage IVA n = 32; 3.6%; stages IIIB-IVA n = 220; 24%) found no benefit with adjuvant chemotherapy, with one analyzing stage IIIB-IVA patients (progression-free survival (PFS) hazard ratio (HR) = 0.84; 95% confidence interval (CI): 0.57-1.23). Three studies (stage IVA n = 71; 5%) found no benefit adding immunomodulator (stage IVA overall survival HR = 3.48; 95% CI: 0.52-23.29), hypoxic cell sensitizer, or immunotherapy (stage III-IVA PFS HR = 0.71; 95% CI: 0.49-1.03) to chemoradiotherapy. One study (stages III-IVA n = 598; 56%) found benefit adding immunotherapy to chemoradiotherapy (stage III-IVA PFS HR = 0.58; 95% CI: 0.42-0.8). One study (stage IVA n = 13; 3.5%) showed benefit with induction chemotherapy. CONCLUSION: Trials have not included substantial IVA patients to draw reasonable conclusions. Despite mixed results for immunotherapy, adjuvant chemotherapy, and induction chemotherapy, the exact benefit for stage IVA patients remains unknown. Future clinical trials should include a greater number of stage IVA cervical cancer patients and analyze them individually.

Management of Dry Eye Toxicity After Treatment With 177Lu-PSMA-617 Radioligand Therapy.

Treatment options for patients with metastatic castration-resistant prostate cancer include use of radioligand therapy with 177Lu-PSMA-617. 177Lu-PSMA-617 is used to target prostate cancer cells selectively by targeting prostate specific membrane antigen (PSMA); however, PSMA is also expressed on lacrimal glands among other tissues. Herein, we report on a case of a Common Terminology Criteria for Adverse Events version 5 grade 3 dry eye event with concomitant blepharitis after administration of 177Lu-PSMA-617. The patient was managed with neomycin-polymyxin-dexamethasone 3.5-10000-0.1 ophthalmic suspension, artificial tears, lubricating ointments, lid scrubs, and oral antihistamines.

Breast Reconstruction Complications After Postmastectomy Proton Radiation Therapy for Breast Cancer.

Purpose: Our purpose was to report complications requiring surgical intervention among patients treated with postmastectomy proton radiation therapy (PMPRT) for breast cancer in the setting of breast reconstruction (BR). Methods and Materials: Patients enrolled on a prospective proton registry who underwent BR with immediate autologous flap, tissue expander (TE), or implant in place during PMPRT (50/50.4 Gy +/- chest wall boost) were eligible. Major reconstruction complication (MRC) was defined as a complication requiring surgical intervention. Absolute reconstruction failure was an MRC requiring surgical removal of BR. A routine revision (RR) was a plastic surgery refining cosmesis of the BR. Kaplan-Meier method was used to assess disease outcomes and MRC. Cox regression was used to assess predictors of MRC. Results: Seventy-three courses of PMPRT were delivered to 68 women with BR between 2013 and 2021. Median follow-up was 42.1 months. Median age was 47 years. Fifty-six (76.7%) courses used pencil beam scanning PMPRT. Of 73 BR, 29 were flaps (39.7%), 30 implants (41.1%), and 14 TE (19.2%) at time of irradiation. There were 20 (27.4%) RR. There were 9 (12.3%) MRC among 5 implants, 2 flaps, and 2 TE, occurring a median of 29 months from PMPRT start. Three-year freedom from MRC was 86.9%. Three (4.1%) of the MRC were absolute reconstruction failure. Complications leading to MRC included capsular contracture in 5, fat necrosis in 2, and infection in 2. On univariable analysis, BR type, boost, proton technique, age, and smoking status were not associated with MRC, whereas higher body mass index trended toward significance (hazard ratio, 1.07; 95% CI, 0.99-1.16; P = .10). Conclusions: Patients undergoing PMPRT to BR had a 12.3% incidence of major complications leading to surgical intervention, and total loss of BR was rare. MRC rates were similar among reconstruction types. Minor surgery for RR is common in our practice.

Five-Year Outcomes of a Phase 1/2 Trial of Accelerated Partial Breast Irradiation Using Proton Therapy for Women With Stage 0-IIA Breast Cancer.

Purpose: We report the results of a phase 1/2 trial of external beam partial breast radiation using proton therapy. Methods and Materials: Eligible patients included stage 0-IIA breast cancer pTis-T2, N0, and size ≤3 cm. Proton beam radiation was used to deliver 3.85 Gy twice daily to 38.5 Gy. The phase 1 portion determined feasibility based on criteria of successful plan creation, treatment delivery, and acute toxicity grade ≥3 in ≤20% of patients. The phase 2 portion had efficacy goals of acute toxicity grade ≥3 in ≤20% of patients and observing physician-rated cosmesis of excellent or good >85% of patients at 2 years. Results: From April 2013 to March 2015, there were 12 patients enrolled onto the phase 1 portion, and the preplanned analysis of feasibility was met in all 4 required criteria. From July 2015 through December 2019 there were 28 patients with 29 treated breasts (1 bilateral) enrolled onto the phase 2 portion of the trial out of 45 originally planned. The trial was closed to accrual because of the coronavirus pandemic and not reopened. Thirty-eight breasts were treated with double-scattering and 3 pencil-beam scanning protons. The median follow-up of the 40 patients is 5.4 years (range, 2.3-8.6 years). There was 1 local recurrence. There was no grade ≥3 acute or late toxicity. At baseline all patients had physician-rated cosmesis good or excellent but at 2 years was excellent in 56%, good in 19%, and fair in 25%. Conclusions: Proton-accelerated partial breast irradiation delivered with a twice-daily fractionation was feasible and associated with very low acute and long-term toxicity. However, the trial did not meet goals for cosmesis outcomes and was closed prematurely. Future study is needed to determine whether pencil-beam scanning protons or different fractionation could improve these outcomes.

Treatment of node-positive endometrial cancer: chemotherapy, radiation, immunotherapy, and targeted therapy.

OPINION STATEMENT: The standard of treatment for node-positive endometrial cancer (FIGO Stage IIIC) in North America has been systemic therapy with or without additional external beam radiation therapy (RT) given as pelvic or extended field RT. However, this treatment paradigm is rapidly evolving with improvements in systemic chemotherapy, the emergence of targeted therapies, and improved molecular characterization of these tumors. The biggest question facing providers regarding management of stage IIIC endometrial cancer at this time is: what is the best management strategy to use with regard to combinations of cytotoxic chemotherapy, immunotherapy, other targeted therapeutics, and radiation that will maximize clinical benefit and minimize toxicities for the best patient outcomes? While clinicians await the results of ongoing clinical trials regarding combined immunotherapy/RT as well as management based on molecular classification, we must make decisions regarding the best treatment combinations for our patients. Based on the available literature, we are offering stage IIIC patients without measurable disease postoperatively both adjuvant chemotherapy and IMRT with carboplatin, paclitaxel, and with or without pembrolizumab/dostarlimab as primary adjuvant therapy. Patients with measurable disease post operatively, high risk histologies, or stage IV disease receive chemoimmunotherapy, and vaginal brachytherapy is added for those with uterine risk factors for vaginal recurrence. In the setting of endometrioid EC recurrence more than 6 months after treatment, patients with pelvic nodal and vaginal recurrence are offered IMRT and brachytherapy without chemotherapy. For measurable recurrence not suitable for pelvic radiation alone, chemoimmunotherapy is preferred as standard of care.

Prognostic Effect of Mismatch Repair Status in Early-Stage Endometrial Cancer Treated With Adjuvant Radiation: A Multi-institutional Analysis.

PURPOSE: The aim of this work was to report the effect of mismatch repair (MMR) status on outcomes of patients with stage I-II endometrioid endometrial adenocarcinoma (EEC) who receive adjuvant radiation therapy. METHODS AND MATERIALS: This is a multi-institutional retrospective cohort study across 11 institutions in North America. Patients with known MMR status and stage I-II EEC status postsurgical staging were included. Overall survival (OS) and recurrence-free survival (RFS) rates were estimated via the Kaplan-Meier method. Univariable and multivariable analyses were performed via Cox proportional hazard models for RFS and OS. Statistical analyses were conducted using SPSS version 27. RESULTS: In total, 744 patients with a median age at diagnosis of 65 years (IQR, 58-71) were included. Most patients were White (69.4%) and had Federation of Obstetrics and Gynecology 2009 stage I (84%) and Federation of Obstetrics and Gynecology grade 1 to 2 (73%). MMR deficiency was reported in 234 patients (31.5%), whereas 510 patients (68.5%) had preserved MMR. External beam radiation therapy with or without vaginal brachytherapy was delivered to 186 patients (25%), whereas 558 patients (75%) received vaginal brachytherapy alone. At a median follow-up of 43.5 months, the estimated crude OS and RFS rates for the entire cohort were 92.5% and 84%, respectively. MMR status was significantly correlated with RFS. RFS was inferior for MMR deficiency compared with preserved MMR (74.3% vs 88.6%, P < .001). However, no difference in OS was seen (90.8% vs 93.2%, P = .5). On multivariable analysis, MMR deficiency status was associated with worse RFS (hazard ratio, 1.86; P = .001) but not OS. CONCLUSIONS: MMR status was independently associated with RFS but not OS in patients with early-stage EEC who were treated with adjuvant radiation therapy. These findings suggest that differential approaches to surveillance and/or treatment based on MMR status could be warranted.

Multicenter Evaluation of Radiation and Immune Checkpoint Inhibitor Therapy in Mucosal Melanoma and Review of Recent Literature.

Purpose: Optimal integration of local therapy and systemic immune therapy for patients with mucosal melanoma (MM) is uncertain. We evaluated treatment patterns and outcomes following radiation therapy (RT) in combination with immune checkpoint inhibition (ICI) in MM. Methods and Materials: Thirty-seven patients with localized (n = 32, 87%) or node-positive (n = 5, 14%) MM were treated across 4 institutions with RT to the primary tumor with or without oncologic resection (n = 28, 76%) and ICI from 2012 to 2020. Recurrence rates were estimated using cumulative incidence in the presence of the competing risk of death. Results: Mucosal sites were head/neck (n = 29, 78%), vaginal (n = 7, 19%), and anorectal (n = 1, 3%). Patients received ICI prior to or concurrent with RT (n = 14, 38%), following RT (n = 5, 14%), or at recurrence (n = 18, 49%). The objective response rate for evaluable patients was 31% for ICI as initial treatment (95% CI, 11%-59%) and 19% for ICI at recurrence (95% CI, 4%-46%). Median follow-up was 26 months for living patients; median overall survival (OS) was 54 months (95% CI, 31 months-not reached). Two-year OS was 85%; distant metastasis-free survival 44%. The 2-year cumulative incidence of local recurrence (LR) was 26% (95% CI, 13%-41%). For 9 patients with unresectable disease, 2-year OS was 88% (95% CI, 35%-98%); LR was 25% (95% CI, 3%-58%). For 5 patients with positive nodes at diagnosis, 2-year OS was 100%; LR was 0%. Conclusions: High rates of local control were achieved with RT with or without oncologic resection and ICI for localized and locally advanced MM. In particular, favorable local control was possible even for patients with unresectable or node-positive disease. Although risk of distant failure remains high, patients with MM may benefit from aggressive local therapy including RT in the setting of immunotherapy treatment.

Insurance status and time to radiation care after pathologic diagnosis for cervical cancer patients.

Delays in starting potentially curative treatment for locally-advanced cervical cancer (LACC) decrease survival. Reasons for these delays are poorly understood. We conducted a retrospective chart review examining disparities in time from diagnosis of LACC to first clinic visit and to initiation of treatment based on insurance status within a single health system. We analyzed time to treatment using multivariate regression, adjusted for race, age, and insurance status. 25% of patients had Medicaid and 53% had private insurance. Having Medicaid was associated with delayed time from diagnosis to seeing a radiation oncologist (Mean 76.9 v. 31.3 days, p = 0.03). However, time from first radiation oncology visit to starting radiation was not delayed (Mean 22.6 v. 22.2 days, p = 0.67). Patients with locally-advanced cervical cancer and Medicaid had over double the time from pathologic diagnosis of cervical cancer to seeing radiation oncology; insurance disparities were not observed in treatment start after seeing radiation oncology. Improved referral and navigation processes for patients with Medicaid are needed to improve timely receipt of radiation and potentially improve survival.

A practical guide to hybrid interstitial/intracavitary brachytherapy for locally-advanced cervical cancer.

PURPOSE: In select cases of locally advanced cervical cancer, a hybrid brachytherapy (HBT) approach consisting of a combined intracavitary (IC)/insterstitial (IS) implant can yield improved target coverage and/or decreased organ at risk dose compared to IC techniques while limiting invasiveness compared to IS techniques. METHODS AND MATERIALS: The technique involves placement of transvaginal and/or perineal needles in addition to the tandem and ring/ovoids using either a specialized applicator or free-hand placement. Following applicator and needle placement, brachytherapy may then be planned using principles similar to IC or IS techniques. During treatment planning, it can be helpful to obtain both MRI and CT imaging, as plastic MRI-compatible needles do not show up well on MRI. RESULTS: In patients where acceptable target coverage cannot be achieved using IC alone or doses to nearby OAR are too high, HBT should be evaluated. HBT can improve both dose to target and OAR while sparing patients the morbidity of perineal template-based interstitial brachytherapy. Specific scenarios where HBT may be preferred include bulky residual primary tumor especially with poor response to EBRT, extension into the lateral parametrium, vaginal extension of tumor, and an asymmetric target. Use of HBT can typically permit extension of dose coverage by an additional 1-2 cm beyond what can be achieved with an IC alone technique. CONCLUSION: HBT allows for improved therapeutic ratio by improving target volume coverage and/or lowering doses to OARs. Brachytherapists should be trained on the practical aspects of administering HBT to be able to offer a less invasive and impactful treatment option when appropriate.

Positron Emission Tomography (PET)/Computed Tomography (CT) Imaging in Radiation Therapy Treatment Planning: A Review of PET Imaging Tracers and Methods to Incorporate PET/CT.

Purpose: Positron emission tomography (PET)/computed tomography (CT) has become a critical tool in clinical oncology with an expanding role in guiding radiation treatment planning. As its application and availability grows, it is increasingly important for practicing radiation oncologists to have a comprehensive understanding of how molecular imaging can be incorporated into radiation planning and recognize its potential limitations and pitfalls. The purpose of this article is to review the major approved positron-emitting radiopharmaceuticals clinically being used today along with the methods used for their integration into radiation therapy including methods of image registration, target delineation, and emerging PET-guided protocols such as biologically-guided radiation therapy and PET-adaptive therapy. Methods and Materials: A review approach was utilized using collective information from a broad review of the existing scientific literature sourced from PubMed search with relevant keywords and input from a multidisciplinary team of experts in medical physics, radiation treatment planning, nuclear medicine, and radiation therapy. Results: A number of radiotracers imaging various targets and metabolic pathways of cancer are now commercially available. PET/CT data can be incorporated into radiation treatment planning through cognitive fusion, rigid registration, deformable registration, or PET/CT simulation techniques. PET imaging provides a number of benefits to radiation planning including improved identification and delineation of the radiation targets from normal tissue, potential automation of target delineation, reduction of intra- and inter-observer variability, and identification of tumor subvolumes at high risk for treatment failure which may benefit from dose intensification or adaptive protocols. However, PET/CT imaging has a number of technical and biologic limitations that must be understood when guiding radiation treatment. Conclusion: For PET guided radiation planning to be successful, collaboration between radiation oncologists, nuclear medicine physicians, and medical physics is essential, as well as the development and adherence to strict PET-radiation planning protocols. When performed properly, PET-based radiation planning can reduce treatment volumes, reduce treatment variability, improve patient and target selection, and potentially enhance the therapeutic ratio accessing precision medicine in radiation therapy.

Acute and long-term toxicity of whole pelvis proton radiation therapy for definitive or adjuvant management of gynecologic cancers.

OBJECTIVE: To characterize long-term toxicity and disease outcomes with whole pelvis (WP) pencil beam scanning proton radiation therapy (PBS PRT) for gynecologic malignancies. METHODS: We reviewed 23 patients treated from 2013 to 2019 with WP PBS PRT for endometrial, cervical, and vaginal cancer. We report acute and late Grade (G)2+ toxicities, graded by Common Terminology Criteria for Adverse Events, Version 5. Disease outcomes were assessed by Kaplan-Meier method. RESULTS: Median age was 59 years. Median follow up was 4.8 years. 12 (52.2%) had uterine cancer, 10 (43.5%) cervical, 1 (4.3%) vaginal. 20 (86.9%) were treated post-hysterectomy. 22 (95.7%) received chemotherapy, 12 concurrently (52.2%). The median PBS PRT dose was 50.4GyRBE (range, 45-62.5). 8 (34.8% had para-aortic/extended fields. 10 (43.5%) received brachytherapy boost. Median follow up was 4.8 years. 5-year actuarial local control was 95.2%, regional control 90.9%, distant control 74.7%, both disease control and progression-free survival 71.2%. Overall survival was 91.3%. In the acute period, 2 patients (8.7%) had G2 genitourinary (GU) toxicity, 6 (26.1%) had gastrointestinal (GI) G2-3 toxicity, 17 (73.9%) had G2-4 hematologic (H) toxicity. In the late period, 3 (13.0%) had G2 GU toxicity, 1 (4.3%) had G2 GI toxicity, 2 (8.7%) had G2-3H toxicity. The mean small bowel V15Gy was 213.4 cc. Mean large bowel V15 Gy was 131.9 cc. CONCLUSIONS: WP PBS PRT for gynecologic malignancies delivers favorable locoregional control. Rates of GU and GI toxicity are low. Acute hematologic toxicity was most common, which may be related to the large proportion of patients receiving chemotherapy.

Comparison of surface dose during whole breast radiation therapy on Halcyon and TrueBeam using Cherenkov imaging.

The emergence of the Halcyon linear accelerator has allowed for increased patient throughput and improved treatment times for common treatment sites in radiation oncology. However, it has been shown that this can lead to increased surface dose in sites like breast cancer compared with treatments on conventional machines with flattened radiation beams. Cherenkov imaging can be used to estimate surface dose by detection of Cherenkov photons emitted in proportion to energy deposition from high energy electrons in tissue. Phantom studies were performed with both square beams in reference conditions and with clinical treatments, and dosimeter readings and Cherenkov images report higher surface dose (25% for flat phantom entrance dose, 5.9% for breast phantom treatment) from Halcyon beam deliveries than for equivalent deliveries from a TrueBeam linac. Additionally, the first Cherenkov images of a patient treated with Halcyon were acquired, and superficial dose was estimated.

Effect of COVID-19 on Gynecologic Oncology Care: A Survey of Practicing Gynecologic Radiation Oncologists in the United States.

Purpose: The COVID-19 pandemic has placed demands and limitations on the delivery of health care. We sought to assess the effect of COVID-19 on the delivery of gynecologic oncologic care from the perspective of practicing radiation oncologists in the United States. Methods and Materials: An anonymous online survey was created and distributed to preidentified radiation oncologists in the United States with clinical expertise in the management of gynecologic patients. The survey consisted of demographic questions followed by directed questions to assess specific patterns of care related to the COVID-19 pandemic. Results: A total of 47 of 96 invited radiation oncologists responded to the survey for a response rate of 49%. Fifty-six percent of respondents reported an increase in locally advanced cervical cancer with no similar increase for endometrial, vulvar, or vaginal patients. Most respondents (66%) reported a pause in surgical management, with a duration of 1 to 3 months being most common (61%). There was a reported increased use of shorter brachytherapy regimens during the pandemic. Most providers (61%) reported caring for at least 1 patient with a positive COVID-19 test. A pause or delay in treatment due to COVID-19 positivity was reported by 45% of respondents, with 55% reporting that patients chose to delay their own care because of COVID-19-related concerns. Total treatment times >8 weeks for patients with cervical cancer were observed by 33% of respondents, but occurred in >25% of patients. Conclusions: Data from this prospectively collected anonymous survey of practice patterns among radiation oncologists reveal that the COVID-19 pandemic resulted in delays initiating care, truncated brachytherapy treatment courses, and a reported increase in locally advanced cervical cancer cases at presentation. These data can be used as a means of self-assessment to ensure appropriate decision making for gynecologic patients during the endemic phase of COVID-19.

Stereotactic Radiation for Oligometastatic and Oligoprogressive Stage IV Breast Cancer: A Case-Based Review.

For decades, the distant progression of breast cancer has been the purview of systemic therapy alone or with low to moderate-dose radiation therapy intended for the palliation of symptomatic metastases. However, for decades there have been anecdotes of long-term disease-free survival with more aggressive local treatment of one or more metastases. The hypothesis of oligometastases is that the treatment of a clinically limited number of distant metastases can change the natural history of stage IV breast cancer. The advance in the technology of stereotactic body radiation (SBRT) has made it more possible to offer a non-invasive, yet potentially disease-modifying, metastases-directed ablative treatment in place of surgery or a palliative radiation regimen. Although there are promising local control and survival outcomes in phase I/II trials, there is still a lack of phase III evidence of ablative SBRT results showing any change in the natural history of metastatic breast cancer. Limited oligometastases may call for an ablative approach with SBRT when definitive long-term local control is needed for the best palliation against symptomatic progression in challenging locations. Some oligometastases that have progression on a certain systemic regimen, while others remain stable or in remission, may also be treated with SBRT in the hopes of prolonging the use of that regimen. Whether SBRT should represent the standard management for stage IV breast cancer of a limited number or of limited progression requires confirmation by phase III data. This review will discuss the data from key clinical trials as it applies to decision making in typical clinical cases considered for potentially ablative SBRT for oligometastases or oligoprogression.

Factors Associated With Travel Distance in the Receipt of Proton Breast Radiation Therapy.

Introduction: Proton radiation therapy (PBT) may reduce cardiac doses in breast cancer treatment. Limited availability of proton facilities could require significant travel distances. This study assessed factors associated with travel distances for breast PBT. Materials and Methods: Patients receiving breast PBT at the University of Pennsylvania from 2010 to 2021 were identified. Demographic, cancer, and treatment characteristics were summarized. Straight-line travel distances from the department to patients' addresses were calculated using BatchGeo. Median and mean travel distances were reported. Given non-normality of distribution of travel distances, Wilcoxon rank sum or Kruskal-Wallis test was used to determine whether travel distances differed by race, clinical trial participation, disease laterality, recurrence, and prior radiation. Results: Of 1 male and 284 female patients, 67.8% were White and 21.7% Black. Median travel distance was 13.5 miles with interquartile range of 6.1 to 24.8 miles, and mean travel distance was 13.5 miles with standard deviation of 261.4 miles. 81.1% of patients traveled less than 30 and 6.0% more than 100 miles. Black patients' travel distances were significantly shorter than White patients' and non-Black or non-White patients' travel distances (median = 4.5, 16.5, and 11.3 miles, respectively; P < .0001). Patients not on clinical trials traveled more those on clinical trials (median = 14.7 and 10.2 miles, respectively; P = .032). There was no difference found between travel distances of patients with left-sided versus right-sided versus bilateral disease (P = .175), with versus without recurrent disease (P = .057), or with versus without prior radiation (P = .23). Conclusion: This study described travel distances and demographic and clinicopathologic characteristics of patients receiving breast PBT at the University of Pennsylvania. Black patients traveled less than White and non-Black or non-White patients and comprised a small portion of the cohort, suggesting barriers to travel and PBT. Patients did not travel further to receive PBT for left-sided or recurrent disease.