BP07 Presentation Time: 4:54 PM

Purpose

As an alternative to the standard 4 to 6 weeks of breast-conserving surgery with whole breast irradiation, a two-day short course accelerated partial breast irradiation (APBI) is available proposed in Triumph-T trial. We present the 2-year follow-up results from a single institution of a 3-fraction APBI delivered using the Strut-Adjusted Volume Implant (SAVI) brachytherapy.

Materials and Methods

Retrospective analysis was conducted to evaluate the efficacy of an ultra-hypofractionated 2-day APBI schedule [22.5 Gy in 3 fractions, Bi-daily, ∼6 hours apart]. Women aged 40 years or older with early-stage breast cancer with diagnosis pTis or pT1-2 underwent breast-conserving surgery and received APBI using high-dose-rate Ir-192 SAVI-brachytherapy. The SAVI applicator is offered in four sizes, each designed to accommodate different cavity volumes: 6-1 mini, 6-1, 8-1, and 10-1. During follow-up (2019-2021), data was gathered on patient and tumor characteristics, treatment summary, oncologic outcomes, and both acute and late treatment-related toxicities, using the Common Terminology Criteria for Adverse Events (CTCAE) v5. Adverse events occurring within 90 days following the completion of APBI were defined as acute, whereas those thereafter were considered late.

Results

A total of 103 female patients (median age, 67 years [range (R), 40-92 years] mainly with pT1 tumors (77.7%) underwent APBI using SAVI-brachytherapy. Seventy-seven percent of the patient had invasive carcinoma histology and 22.3% were Ductal carcinoma in situ (DCIS). Median tumor size was 10 mm [R, 1.0-30.0 mm]. There were 91.3% estrogen positive and 84.5% progesterone receptors positive tumors, while Her2neu was positive in 1.9% of cases. Post-APBI, 88.3% of patients received adjuvant hormonal therapy and 7.8% received adjuvant chemotherapy. With a median follow-up of 36.4 months [R, 2.3-53.0 months], the most commonly reported toxicities were hyperpigmentation (47.6%) followed by skin induration (32.0%). Acute grade 1 toxicities were seen in 35.0% of cases, including 27.2% hyperpigmentation, 7.8% skin induration, 6.8% breast pain, 2.9% fatigue, 1.9% moist desquamation, and 1.0% erythema. Late grade 1 toxicities were seen in 53.4% of cases, including 28.2% skin induration, 24.3% hyperpigmentation, 17.5% breast pain, 4.9% fatigue, 1.9% telangiectasia, and 1.0% moist desquamation. No acute or late grade 2+ toxicities were observed. Fifteen patients developed late grade 1 fat necrosis within a median 17.3 months [R, 4.2-38.2 months], 12 were asymptomatic and 3 were symptomatic. Six patients developed breast tissue fibrosis. There were 2 (1.9%) local recurrences. Two-year overall survival following APBI was 98.1%.

Conclusions

Retrospective analysis of 2-year follow-up of 103 patients treated at our center using 3-fraction APBI with SAVI- brachytherapy, after breast-conserving surgery demonstrates feasibility and shows excellent oncologic and cosmetic outcomes. APBI presents a viable alternative to WBI in terms of treatment efficacy and is well tolerated by patients.