B. Gui1,2, O. E. Ojo1,2, L. Ottensoser1,2, W. J. Talcott1,3, B. Parashar1, L. Potters3,4, and G. Wernicke1,3; 1Northwell, Lake Success, NY, 2Department of Radiation Medicine, Northwell, Lake Success, NY, 3Department of Radiation Medicine, Northwell, New York, NY, 4Northwell, New Hyde Park, NY
Purpose/Objective(s): Ultra-hypofractionated radiotherapy (UHFRT) (1 week of RT in 5 fx) has been shown to be effective in controlling local recurrence in women with early-stage breast cancer as per the FAST-Forward trial. However, its role in the subset of older women was not specifically reported. Further, many older women have diminished compliance with endocrine therapy (ET). This study aims to investigate the initial outcomes of UHFRT in older patients with low-risk breast cancer who are potential candidates for omission of RT. Materials/
Methods: After IRB approval, we assessed outcomes of consecutive women treated in the department of radiation medicine at Northwell Health with breast conserving surgery and adjuvant 5-fx UHFRT regimens [whole breast 26Gy/5fx or accelerated partial breast irradiation (APBI) 26-30Gy/5fx] between Jan 2020 and Feb 2024. Inclusion criteria were age= 65 years, Grade 1 or 2, T1-T2 up to 3 cm invasive breast cancer, axillary node-negative, clear margins, hormone receptor-positive, Her-2 negative. Compliance with RT and ET, toxicity, cosmetic outcomes, and IBTR were analyzed. Descriptive statistics, t-test and Chi-square test were performed, using SAS OnDemand for academics 2024 version. Results: Of 1258 women with early-stage breast cancer treated at our center, 71 women met low-risk inclusion criteria and were treated with UHFRT: 43 (61%) with whole breast and 28 (39%) with APBI. Median age was 73 years (range, 65 - 91 years). Median tumor size was 0.8cm (range, 0.12 – 2.8 cm). While compliance with UHFRT was 100%, compliance with ET was 24% (either due to refusal or termination of ET due to side effects). At a median follow up of 10 months (range, 1 - 37 months), there was no IBTR in the entire cohort. There were no Grades 3 or 4 toxicities. Grade 2 acute toxicities, late toxicities, and cosmetic outcomes (induration) with UHFRT+ET vs UHFRT alone were 2% vs. 0%, 2% vs. 0%, 0% vs. 5.9% respectively, and p=0.28, 1.00, 0.24, respectively. Despite no significant difference in age and baseline performance status (p=0.19 and 0.33), higher Grades 1 and 2 acute fatigue was observed in patients who were not compliant with ET after UHFRT (UHFRT vs UHFRT +ET 36% vs. 13%, p=0.02). Conclusion: These results demonstrate that UHFRT with FastForward and APBI regimens offer a convenient and easily tolerated treatment approach for older women who chose to reduce the rate of IBTR. Further, in women with diminished compliance with ET, there was 100% compliance with UHFRT. UHFRT resulted in encouraging local control, compliance, and cosmetic results (FAST-Forward showed 5.6% induration). Further prospective studies are necessary to confirm our initial findings.
