Long-Term Cancer Outcomes From Study NRG Oncology/RTOG 9517: A Phase 2 Study of Accelerated Partial Breast Irradiation With Multicatheter Brachytherapy After Lumpectomy for Early-Stage Breast Cancer

Abstract

Purpose To examine 10-year rates of local, regional, and distant recurrences, patterns of recurrence, and survival rates for breast cancer patients enrolled on Study NRG Oncology/Radiation Therapy Oncology Group 9517, a multi-institutional prospective trial that studied one of the earliest methods of accelerated partial breast irradiation (APBI), multicatheter brachytherapy (MCT). Methods and Materials Eligibility included stage I/II unifocal breast cancer <3 cm in size after lumpectomy with negative surgical margins and 0 to 3 positive axillary nodes without extracapsular extension. The APBI dose delivered was 34 Gy in 10 twice-daily fractions over 5 days for high-dose-rate (HDR); and 45 Gy in 3.5 to 5 days for low-dose-rate (LDR) brachytherapy. The primary endpoint was HDR and LDR MCT reproducibility. This analysis focuses on long-term ipsilateral breast recurrence (IBR), contralateral breast cancer events (CBE), regional recurrence (RR), and distant metastases (DM), disease-free, and overall survival. Results The median follow-up was 12.1 years. One hundred patients were accrued from 1997 to 2000; 98 were evaluable; 65 underwent HDR and 33 LDRMCT. Median age was 62 years; 88% had T1 tumors; 81% were pN0. Seventy-seven percent were estrogen receptor and/or progesterone receptor positive; 33% received adjuvant chemotherapy and 64% antiendocrine therapy. There have been 4 isolated IBRs and 1 IBR with RR, for 5.2% 10-year IBR without DM. There was 1 isolated RR, 1 with IBR, and 1 with a CBE, for 3.1% 10-year RR without DM. The 10-year CBE rate was 4.2%, with 5 total events. Eleven patients have developed DM, 8 have died of breast cancer, and 22 have died from other causes. The 10-year DFS and OS rates are 69.8% and 78.0%, respectively. Conclusion This multi-institutional, phase 2 trial studying MCT-APBI continues to report durable in-breast cancer control rates with long-term follow-up.

The Role of Brachytherapy in the Treatment of Breast Cancer

“…In LDR BT, radiation sources deliver doses continuously with dose rates between 0.4 and 2 Gy/h over a few days. LDR regimens were mainly used in early APBI trials where doses of up to 45 Gy in 4.5 days were used [12]. While radiobiologically advantageous, LDR cannot be delivered in an afterloading setup.…”

Three-Fraction Intracavitary Accelerated Partial Breast Brachytherapy: Early Provider and Patient-Reported Outcomes of a Novel Regimen

“…There is no current consensus on the ideal APBI treatment approach [3][4][5][6][7][8][9][10][11]. Intracavitary catheter-based partial breast brachytherapy (ICBB) is one attractive modality for APBI administration.…”

The evolution of adjuvant radiation therapy for early‐stage and locally advanced breast cancer

“…Patients received either low‐dose‐rate (LDR) brachytherapy (45 Gy in 3.5 to 5 days) or high‐dose‐rate (HDR) brachytherapy (34 Gy in 10 fractions delivered twice daily). Among 98 evaluable patients, the 10‐year ipsilateral breast recurrence rate was 5.2% . A larger multi‐institutional phase III noninferiority trial randomized 1184 patients to either SF‐WBI or APBI.…”