Abstract P3-12-19: Impact of young age on local control after partial-breast irradiation in early-stage breast cancer

Abstract

Abstract Background: Although the rate of breast-conserving surgery (BCS) increased, the receipt of adjuvant radiotherapy after BCS decreased especially for young patients. The long-term daily visit to radiation facilities must be the most relevant barriers to receiving radiation therapy. The use of partial-breast irradiation (PBI) is considered an alternative option. However, there are limited data to be seen how safe PBI is as an option of adjuvant radiation therapy in young patients compared with whole-breast irradiation (WBI). In this report, we reviewed our single-institution experience with PBI compared with WBI in young breast cancer patients. Methods: We evaluated 443 consecutive patients with T≤3-cm N0–1 breast cancer who underwent breast-conserving therapy (BCT) between November 2007 and May 2015. 268 patients received PBI using interstitial multicatheter brachytherapy. The interstitial brachytherapy was performed in an accelerated fashion with a dose of 32 Gy in eight fractions over 5-6 days. 185 patients received WBI with a dose of 50 Gy in fractions of 2 Gy. Patients with risk factors such as positive margins and young age received a subsequent 10 Gy boost to the tumor bed, and the regional nodal irradiation was added in patients with ≥ 4 positive nodes. Patients who underwent neoadjuvant chemotherapy were excluded from the analysis. Our primary objective was to assess outcome rates of ipsilateral breast tumor recurrence (IBTR), disease-free survival (DFS), and overall survival (OS), and compare the patterns of treatment failures between the cohorts. Results: Patients aged <50 years with a minimum follow-up period of 6 months were selected for the analysis. Of those patients who could be completely followed, there were 95 women receiving PBI and 81 women receiving WBI. In PBI cohort, 4 patients also received WBI because of adverse histological features with positive nodes or positive margins by final pathology. Median follow-up was 4.0 years for PBI patients and 3.9 years for WBI patients. Median age was 43.9 years old for PBI and 42.1 years old for WBI cohort. Mean tumor size was equivalent for the cohorts (12 mm). Positive lymph nodes were seen more frequently in WBI cohort (9.5% and 29.6%, p < 0.05). There was no significant difference in the 3-year probability of disease-free survival (97.4% and 98.1% for PBI and WBI, respectively; p = 0.95). No breast cancer related death was observed. With our follow-up period, there were 5 IBTR (2.8%). Of these IBTRs, 4 were true recurrences (2 were in PBI and 2 were in WBI). There was 1 elsewhere recurrence in PBI cohort. The actual rate of IBTR was 3.2% and 2.5% in PBI and WBI, respectively (p = 0.64). Conclusions: We observed equivalent IBTR rates between PBI and WBI cohorts in young breast cancer patients. If there are no differences in survival between the two radiotherapy regimens, PBI may be a better option than WBI after BCS in such a population. To our knowledge, this is the first report describing that the efficacy of PBI after BCS is comparable with WBI in young breast cancer patients in Asia. However, our data are limited by our short median follow-up with small number of patients. The application of PBI should still be carefully considered until mature Phase III trial data are available. Citation Format: Sato K, Mizuno Y, Fuchikami H, Takeda N, Kato M. Impact of young age on local control after partial-breast irradiation in early-stage breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-19.