Thirty-Year Single Institution Experience of Accelerated Partial Breast Irradiation for Early-Stage Breast Cancer

Abstract

Accelerated partial breast irradiation (APBI) can reduce treatment time and spare normal breast tissue. Techniques for APBI include applicator-based, external beam radiotherapy (EBRT), intra-operative radiotherapy (IORT), and interstitial implant-based. Data comparing these various APBI modalities and associated outcomes are lacking in the literature. We conducted a single-institution retrospective analysis of patients treated with APBI to compare treatment techniques and report outcomes.Patients treated with APBI between 1990 and 2019 were included. Baseline patient characteristics, clinical and pathological features, treatment details, and clinical outcomes were retrospectively reviewed using a single-institution database. Outcomes were updated through August 2020. Statistical methods included Kruskal-Wallis test, Fisher's exact test, chi-square test of independence, and Kaplan-Meier analysis.A total of 926 APBI cases were analyzed, a majority of which were invasive ductal carcinoma (50.6%). Comparing applicator-based to EBRT, IORT, and implant-based, there was no difference in overall survival, freedom from local recurrence, or freedom from mastectomy (Table 1). 5-, 10-, and 25-year cumulative incidence of ipsilateral breast tumor recurrence (IBTR) was 1.5% (0.87-2.5%), 3.3% (2.3-4.7%), and 5.2% (3.9-6.7%), with no difference between treatment techniques. The median follow-up time was 121.6 months (66-165.7 months). Cosmesis was good/excellent in 91%, 84%, and 93%, for applicator, EBRT, and interstitial techniques, respectively. Late toxicities assessed included pigmentary changes, telangiectasias, induration/fibrosis, and fat necrosis. The majority of late toxicities were none or Grade 1, with less than 10% of patients experiencing Grade 2 or greater toxicity.With our 30-year single-institution APBI experience using various treatment techniques, long term outcomes of both disease control and local morbidity demonstrate that the various APBI techniques are equally effective for suitable early-stage breast cancer patients. As evolving radiotherapy paradigms incorporate more shortened time-course treatments, these results affirm that APBI remains a viable alternative for such favorable patients.