Long-Term Outcomes of Multimodality Accelerated Partial Breast Irradiation for Ductal Carcinoma In Situ.

PURPOSE

To report long-term institutional outcomes for ductal carcinoma in situ treated with accelerated partial breast irradiation (APBI) using multiple modalities as a part of breast-conserving therapy.

METHODS AND MATERIALS

From January 2001 to April 2019, 240 patients with stage 0 breast cancer were treated with breast-conserving surgery (BCS) and adjuvant APBI at our institution. Based on the 2024 American Society for Radiology and Oncology (ASTRO) APBI guidelines, 170 patients were "recommended," 68 were "conditionally recommended," and 2 were "not recommended" for APBI. A total of 102 patients were treated with linear accelerator-based external beam radiation therapy, 38 with magnetic resonance image-guided external beam radiation therapy (MRgEBRT), 49 with multicatheter interstitial implant (ISI) brachytherapy, and 51 with intracavitary applicator brachytherapy (strut-adjusted volume implant). Patients treated with external beam radiation therapy received 3850 cGy in 10 fractions twice a day. Patients treated with ISI or strut-adjusted volume implant received 3400 cGy in 10 fractions twice a day. Recurrence and survival were calculated using the Kaplan-Meier method. Cosmesis was scored by the Harvard criteria.

RESULTS

At a median follow-up of 11.5 years (range, 1.2-17.8 years), the overall and cause-specific survival rates were 94.8% and 100%, respectively. The 10-year ipsilateral breast tumor recurrence rate was 3.8%. There were 9 observed ipsilateral breast tumor recurrences with 1 concurrent ipsilateral regional lymph node recurrence. No other breast failures, regional recurrences, or distant metastases were noted. Breast cancer-specific survival (BCSS) was 99.6% at the time of analysis. There was no statistically significant difference in overall survival or recurrence rates between the different treatment modalities. Cosmesis was excellent or good in 90% of cases without a statistically significant difference between the treatment method, 2024 American Society for Radiology and Oncology APBI criteria, or the 2022 American Brachytherapy Society (ABS) APBI acceptability categories.

CONCLUSIONS

APBI as a component of breast-conserving therapy for pure ductal carcinoma in situ is associated with excellent survival rates, local control, and cosmetic outcomes regardless of radiation therapy modality.