Validation of Patient-Reported Outcomes in Patients With Nonmetastatic Breast Cancer Receiving Comprehensive Nodal Irradiation in the RadComp Trial.

PURPOSE: Our purpose was to evaluate the measurement properties of patient-reported outcome (PRO) measures used in the ongoing RadComp pragmatic randomized clinical trial (PRCT). METHODS AND MATERIALS: The deidentified and blinded data set included 774 English-speaking female participants who completed their 6-month posttreatment assessment. Eleven PRO measures were evaluated, including the Trial Outcome Index from the Functional Assessment of Cancer Therapy-Breast (FACT-B), Satisfaction with Breast Cosmetic Outcomes, the BREAST-Q, and selected Patient-Reported Outcomes Measurement Information System (PROMIS) measures. PROs were measured at 3 timepoints: baseline, completion of radiation therapy (RT), and 6 months post-RT. Ten variables were used as validity anchors. Pearson or Spearman correlations were calculated between PROs and convergent validity indicators. Mean PRO differences between clinically distinct categories were compared with analysis of variance methods (known-groups validity). PRO change scores were mapped to change in other variables (sensitivity to change). RESULTS: Most correlations between PROs and validity indicators were large (≥0.5). Mean score for Satisfaction with Breast Cosmetic Outcomes was higher (better) for those with a lumpectomy compared with those with a mastectomy (P < .001). Mean scores for the FACT-B Trial Outcome Index and for PROMIS Fatigue and Ability to Participate in Social Roles and Activities were better for those with good baseline performance status compared with those with poorer baseline performance status (P < .05). At completion of RT and post-RT, mean scores for Satisfaction with Breast Cosmetic Outcomes and BREAST-Q Radiation were significantly different (P < .001) across categories for all Functional Assessment of Chronic Illness Therapy -Treatment Satisfaction - General items. There were medium-sized correlations between change scores for FACT-B Trial Outcome Index, Fatigue, Anxiety, and Ability to Participate in Social Roles and change scores in the Visual Analog Scale. CONCLUSIONS: For patients with nonmetastatic breast cancer receiving radiation in the RadComp PRCT, our findings demonstrate high reliability and validity for important PRO measures, supporting their psychometric strength and usefulness to reflect the effect of RT on health-related quality of life.

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.

Temporal Trends and Factors Associated with Receipt of Post-mastectomy Radiation After Neoadjuvant Chemotherapy in Women with cT3 Breast Cancer.

INTRODUCTION: Given the potential impact of increasingly effective neoadjuvant chemotherapy (NACT) on post-mastectomy radiotherapy (PMRT) recommendations, we examined temporal trends in post-NACT PMRT for cT3 breast cancer. METHODS: We identified women ≥ 18 years in the National Cancer Database (NCDB) diagnosed 2004-2019 with cT3N0-1M0 breast cancer treated with chemotherapy and mastectomy. Multivariable logistic regression and Cox proportional hazards models were used to estimate associations between pathologic NACT response [complete response (CR), partial response (PR), or no response (NR); or disease progression (DP)] and PMRT and between PMRT and overall survival (OS), respectively. RESULTS: We identified 39,901 women (Asian/Pacific Islander 1731, Black 5875, Hispanic 3265, White 27,303). Among cN0 patients with CR, PMRT rates declined from 67% in 2004 to 35% in 2019 but remained unchanged for patients with DP. Relative to NR, CR [odds ratio (OR) 0.36, 95% confidence interval (CI) 0.29-0.46] and PR (OR 0.44, 95% CI 0.36-0.55) in cN0 patients were associated with lower odds of PMRT while DP (OR 1.33, 95% CI 1.05-1.69) was associated with higher odds. Among cN1 patients, PMRT rates decreased from 90% to 73% for CR between 2005 and 2019 and increased from 76% to 82% for DP between 2004 and 2019. Relative to NR, CR (OR 0.78, 95% CI 0.63-0.95) was associated with lower odds of PMRT while DP (OR 1.93, 95% CI 1.58-2.37) was associated with higher odds. PMRT was associated with improved OS among cN1 patients (hazard ratio (HR) 0.77, 95% CI 0.67-0.88). CONCLUSION: CR was associated with decreased PMRT receipt over time, while temporal trends following PR and DP differed by cN status, suggesting that nodal involvement guided PMRT receipt more than in-breast disease.

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.

Nursing Telemedicine Educational Encounters: Improved Patient Satisfaction in Radiation Therapy Clinics.

BACKGROUND: Nurse-led education can improve patient satisfaction, and telemedicine has increased patient access during the COVID-19 pandemic. OBJECTIVES: The aim of this article was to investigate how nursing telemedicine educational visits influence patient satisfaction. METHODS: Patients receiving standard of care in-person education for breast cancer radiation therapy (RT) between January 2019 and June 2019 comprised the preintervention cohort. After July 2019, patients received the same information virtually and represented the postintervention cohort. Press Ganey surveys were used to evaluate patient satisfaction, t tests were performed to differentiate satisfaction scores, and f tests were calculated to determine differences in the variances of response. FINDINGS: Patient satisfaction increased in the postintervention cohort for what to expect during RT, how to manage side effects, and nurses' attentiveness to patient questions and worries. There was decreased variance in patient satisfaction in the postintervention group for quality of care received from nurses and caring manner of nurses.

Proton beam therapy causing pericarditis - a rare case of radiation induced cardiotoxicity.

Acute pericarditis is caused by the inflammation of the pericardium which can result in an effusion around the heart. Proton beam therapy causing radiation-induced pericarditis is not a well-known cause of pericarditis. We present a case of a patient with Li-Fraumeni Syndrome who developed acute onset pericarditis, presumed to be secondary to proton beam therapy.

Adjuvant Photodynamic Therapy, Mediated via Topical Versus Systemic Administration of 5-Aminolevulinic Acid for Control of Murine Mammary Tumor after Surgical Resection.

Treatment de-escalation is sought in the management of precursor lesions of early stage breast cancer, driving the appeal of adjuvant modalities to lumpectomy that reduce toxicity and minimally detract from patient quality of life. We investigate photodynamic therapy (PDT), with the photosensitizing prodrug, 5-aminolevulinic acid (ALA), as adjuvant therapy to complete resection of murine mammary tumor (propagated from TUBO cells). ALA was delivered either systemically (oral, 250 mg kg-1 ) at 5 h before 632 nm illumination or topically (20% solution) to the resection site at 10 min before light delivery to 135 J cm-2 . Treatment with either oral-ALA-PDT (oALA-PDT) or topical-ALA-PDT (tALA-PDT) to the mammary fat pad after TUBO complete resection (CR) produced long-term tumor control with 90-day complete response rates of 21% and 32%, respectively, compared to control rates of 0-5% in mice receiving only CR. Thus, CR/tALA-PDT was equipotent to CR/oALA-PDT despite ~10-fold lower levels of ALA-induced protoporphyrin XI as photosensitizer after topical versus oral-ALA administration. CR/oALA-PDT produced more vascular damage, greater proportion of tissue-resident neutrophils and stronger inflammation when compared to CR/tALA-PDT. Collectively, these data provide rationale for ongoing investigation of ALA-PDT as adjuvant therapy after lumpectomy for increased probability of local control in the treatment of breast cancer.

Safety of cyclin-dependent kinase4/6 inhibitor combined with palliative radiotherapy in patients with metastatic breast cancer.

INTRODUCTION: Cyclin-dependent kinase (CDK)4/6 inhibitor is a first-line therapy for metastatic ER+/HER2-breast cancer. However, there are limited data on safety of combined radiotherapy (RT) and CDK4/6 inhibition. METHODS: We conducted a retrospective study of women with metastatic breast cancer who received palliative RT within 14 days of CDK4/6 inhibitor use. The primary endpoint was toxicity per Common Terminology Criteria for Adverse Events v5. Secondary endpoints were pain response and local control based on clinical assessment and imaging. RESULTS: Thirty patients underwent 36 RT courses with palbociclib (n = 34 courses, 94.4%) or abemaciclib (n = 2, 5.6%). RT was delivered before, concurrently or after CDK4/6 inhibitors in 7 (19.4%), 8 (22.2%), and 21 (58.3%) of cases with median 3.5 days from RT to closest CDK4/6 inhibitor administration. Median RT dose was 30Gy (range 8-40.05Gy). Treated sites included brain (n = 5, 11.6%), spine (n = 19, 44.2%), pelvis (n = 9, 20.9%), other bony sites (n = 6, 14.0%) and others (n = 4, 9.3%). No acute grade ≥3 non-hematologic toxicity occurred. No increased hematologic toxicity was attributable to RT with grade 3 hematologic toxicities rates 16.7%, 0%, and 6.7% before, during, and 2 weeks after RT completion. All but one patient (29/30) achieved symptom relief. Local control rates were 94.4%, 91.7% at 6 and 12 months. CONCLUSIONS: The use of RT within 2 weeks of CDK4/6 inhibitors had low acceptable toxicity and high efficacy, suggesting that it is safe for palliation of metastatic breast cancer.

Proton Reirradiation for Locoregionally Recurrent Breast Cancer.

PURPOSE: Local-regional recurrence (LRR) of breast cancer after prior adjuvant radiation (RT) can present a clinical challenge. Proton therapy is recommended by the American Society for Radiation Oncology in cases where reirrradiation is needed; however, data are limited. We present the toxicity and outcomes after reirradiation for local-regional recurrence of breast cancer with proton therapy. METHODS AND MATERIALS: A single-institution retrospective review identified patients with the following criteria: LRR of breast cancer, prior photon radiation to the same region, proton beam reirradiation, and definitive intent. Surgery or systemic therapy at the time of recurrence was used when indicated. The log-rank test was used to compare Kaplan-Meier survival estimates. Kruskal-Wallis tests were performed to compare worst reported toxicities with clinical variables. RESULTS: The population included 27 patients with a history of prior radiation and treated with proton therapy for LRR between 2012 and 2019. The median interval between courses was 9.7 years. Proton reirradiation regimens included whole breast/chest wall (WB/CW) with regional nodal RT (22/27), nodal RT alone (2/27), or WB/CW alone (3/27). The median dose was 51 Gy, and the most common fractionation was 1.5 Gy twice daily. Median follow-up after reirradiation was 16.6 months. Acute grade 3 toxicities included dermatitis in 2 patients and breast pain in 2 patients. Grade 2 or higher late toxicities included 6 G2 rib fractures and 1 G2 brachial plexopathy, 1 G3 dermatitis, 1 G3 breast pain, and 1 G4 dermatitis. Twelve patients had new documented recurrences of which 1 was a second in-field LRR, and there were 7 deaths. CONCLUSIONS: Proton salvage reirradiation to median 51 Gy in 1.5 Gy twice daily appears to be safe with acceptable acute and late toxicity, and effective with >95% local-regional control.

Immediate Breast Reconstruction for Inflammatory Breast Cancer: Trends in Use and Clinical Outcomes 2004-2016.

INTRODUCTION: National guidelines specify against immediate breast reconstruction (IBR) among inflammatory breast cancer (IBC) patients. However, limited data exist regarding this practice. We report practice patterns and oncologic outcomes among nonmetastatic IBC patients receiving trimodality therapy, with or without IBR. METHODS: Using the National Cancer Database, we identified nonmetastatic IBC patients treated with trimodality therapy from 2004 to 2016. Primary outcome was overall survival (OS), assessed on unadjusted analysis using Kaplan-Meier estimates and on adjusted analysis using multivariable Cox proportional hazards and inverse probability weighting (IPW) models. OS analysis was also conducted with propensity score matched (PSM) cohorts. Secondary outcomes included IBR utilization rates, time to postmastectomy radiotherapy (PMRT), and surgical outcomes. RESULTS: 6589 women were included, including 5954 (90.4%) non-reconstructed and 635 (9.6%) IBR. Among IBR recipients, 250 (39.4%) underwent autologous reconstruction, 171 (26.9%) underwent implant-based reconstruction, and 214 (33.7%) unspecified. IBR utilization increased from 6.3% to 10.1% from 2004 to 2016 at a 4% average annual growth rate (P < 0.001). Median follow-up was 43 and 45 months for IBR and non-reconstructed patients, respectively (P = 0.29). On Cox multivariable analysis, IBR was associated with improved OS (HR 0.63, 95% CI 0.44-0.90, P = 0.01), but this association was not significant on IPW analysis (P = 0.06). In PSM cohorts, this association remained significant (HR 0.60, 95% CI 0.40-0.92, P = 0.02). Margin status, time to PMRT, 30-day readmission, and 30-/90-day mortality did not differ between groups (all P > 0.05). CONCLUSION: Although not endorsed by national guidelines, IBR is increasing among IBC patients; however, more granular data are needed to determine oncologic safety.

Per-fraction positional and dosimetric performance of prone breast tangential radiotherapy on Halcyon™ linear accelerator assessed with daily rapid kilo-voltage cone beam computed tomography: a single-institution pilot study.

BACKGROUND: This study investigates daily breast geometry and delivered dose to prone-positioned patients undergoing tangential whole breast radiation therapy (WBRT) on an O-ring linear accelerator with 6X flattening filter free mode (6X-FFF), planned with electronic compensation (ECOMP) method. Most practices rely on skin marks or daily planar image matching for prone breast WBRT. This system provides low dose daily CBCT, which was used to study daily robustness of delivered dose parameters for prone-positioned WBRT. METHODS: Eight patients treated with 16-fraction prone-breast WBRT were retrospectively studied. Planning CTs were deformed to daily CBCT to generate daily synthetic CTs, on which delivered dose distributions were calculated. A total of 8 × 16 = 128 synthetic CTs were generated. Consensus ASTRO definition was used to contour Breast PTV Eval for each daily deformed CT. Breast PTV Eval coverage (V90%) and hotspot (V105% and Dmax) were monitored daily to compare prescription dose with daily delivered dose. Various predictors including patient weight, breast width diameter (BWD), and Dice similarity coefficient (DSC) were fit into an analysis of covariance model predicting V90% and V105% deviation from prescribed (ΔV90%, ΔV105%). Statistical significance is indicated with asterisks (* for p < 0.05; ** for p < 0.001). RESULTS: Daily delivered Breast PTV Eval V90% was moderately smaller than prescribed (median ΔV90% = - 0.1%*), while V105% was much larger (median ΔV105% = + 10.1%** or + 92.4 cc**). Patient's weight loss correlated with significantly increased ΔV105% (+ 4.6%/ - 1% weight, R2 = 0.4**) and moderately decreased ΔV90% (- 0.071%/ - 1% wt., R2 = 0.2**). Comprehensive ANCOVA models indicated three factors affect ΔV90% and ΔV105% the most: (1) BWD decrease (- 0.09%* and + 10%**/ - 1 cm respectively), (2) PTV Eval volume decrease (- 0.4%** and + 9%**/ - 100 cc), and for ΔV105% only, (3) the extent of breast deformation (+ 10%**/ - 0.01 DSC). Breast PTV Eval volume also decreased with time (- 2.21*cc/fx), possibly indicating seroma resolution and increase in V105% over time. CONCLUSIONS: Daily CBCT revealed key delivered dose parameters vary significantly for patients undergoing tangential prone breast WBRT planned with ECOMP using 6X-FFF. Patient weight, BWD, and breast shape deformation could be used to predict dosimetric variations from prescribed. Preliminary findings suggest an adaptive plan based on daily CBCT could reduce excessive dose to the breast.

Factors Associated With Fatigue in Patients with Breast Cancer Undergoing External Beam Radiation Therapy.

PURPOSE: Cancer-related fatigue (CRF), a prevalent symptom among cancer patients, is a side effect of external beam radiation therapy (EBRT). Even when targeting organs unrelated to caloric intake or the central nervous system, radiation therapy can increase CRF, a poorly understood toxicity resulting from patient-specific, systemic therapy-related, and radiation-specific factors. We sought to determine factors associated with fatigue among patients receiving EBRT for breast cancer. METHODS AND MATERIALS: To determine the variables associated with fatigue among patients with nonmetastatic breast cancer, we retrospectively analyzed prospectively collected toxicity data for a cohort of 1286 adult females with breast cancer who began curative-intent EBRT between April 4, 2010, and October 10, 2017. We hypothesized certain variables are associated with provider-reported Common Terminology Criteria for Adverse Events version 4 fatigue, graded 0 to 3, at baseline and over the course of radiation treatment. RESULTS: All patients were women, with a median age of 57 (range, 24-90). Mean fatigue was low (0.35 [95% confidence interval, 0.32-0.38]) at the start of radiation, increasing weekly and peaking at week 6 (0.85 [0.81-0.90]). Baseline fatigue was associated with higher American Joint Committee on Cancer stage (P < .001), N-stage (P < .001), anxiolytics (P < .001), anticonvulsants (P = .002), antidepressants (P = .006), antihistamines (P < .001), and antipsychotics (P < .001). Chemotherapy was not associated with baseline fatigue. Over the course of treatment, on multivariable analysis, only lower dose per fraction (P < .001) was significantly associated with increasing fatigue. In a subgroup analysis, heart and lung mean, V5, and V20 doses were not found to be associated with increasing fatigue. CONCLUSIONS: This work informs clinicians which factors are associated with CRF at the start of radiation therapy (more advanced disease and prescription of anxiolytics, anticonvulsants, antidepressants, antihistamines, and antipsychotics) and increase CRF over the course of radiation (smaller fraction size). This extensive analysis of factors associated with fatigue provides further evidence that hypofractionated radiation therapy for breast cancer is associated with less acute toxicity than conventionally fractionated treatment.

Frequency of radiation-induced malignancies post-adjuvant radiotherapy for breast cancer in patients with Li-Fraumeni syndrome.

PURPOSE: Women with Li-Fraumeni syndrome (LFS), a cancer predisposition syndrome caused by germline mutations in TP53, have an over 50% risk of developing breast cancer by age 70. Patients with LFS are at risk for radiation-induced malignancies; however, only small case series have prior investigated radiation risks in the treatment of breast cancer. We therefore aimed to investigate the risk of malignancy in breast cancer patients with LFS following adjuvant radiotherapy. METHODS: A single-institution retrospective chart review was conducted for female breast cancer patients with confirmed germline TP53 mutation. The frequency of radiation-induced malignancies in LFS patients was compared to non-LFS breast cancer cases reported in the Penn Medicine Cancer Registry via statistical analyses. RESULTS: We identified 51 female LFS breast cancer patients with 74 primary diagnoses. Fifty-seven% had a history of breast cancer only, and 25% had breast cancer as their presenting diagnosis of LFS. LFS-associated breast cancers were predominantly invasive ductal carcinoma (48%) and HER2+ (58%). Twenty patients underwent adjuvant radiotherapy with a median follow-up of 12.5 (2-20) years. Of 18 patients who received radiation in a curative setting, one (6%) patient developed thyroid cancer, and one (6%) patient developed sarcoma in the radiation field. This risk for radiation-induced malignancy associated with LFS was higher for both sarcoma and thyroid cancer in comparison with the control cohort. CONCLUSIONS: We found a lower risk of radiation-induced secondary malignancies in LFS breast cancer patients than previously reported in the literature (33% risk of radiation-induced sarcoma). These findings suggest that LFS may not be an absolute contraindication for radiotherapy in breast cancer. The potential risk for locoregional recurrence without radiotherapy must be weighed against the long-term risk for radiation-induced malignancies in consideration of adjuvant radiotherapy for LFS breast cancer patients.