Accelerated partial breast irradiation (APBI) after breast-conserving surgery is as effective as whole breast irradiation (WBI) for low-risk breast cancer patients, according to a study presented at the 2015 American Society for Radiation Oncology (ASTRO) Annual Meeting, held in San Antonio, Texas.
APBI was as effective as WBI in local control, disease-free survival (DFS), and overall survival rates.
The phase III randomized trial enrolled 1,184 women aged 40 and older with low-risk invasive breast cancer and ductal carcinoma in situ who received breast-conserving surgery. Patients received either 50 Gy WBI with a tumor bed boost of 10 Gy or APBI using multicatheter brachytherapy. The median follow-up was 6.6 years. The median age of women on study was 62 years.
Five-year local recurrence rates were 1.4% and 0.9% in the APBI and WBI arms, respectively (P = .42). A second primary ipsilateral breast cancer of different histology occurred in 1.1% of patients in the WBI arm compared with 0.9% in the APBI arm (P = .91).
The 5-year DFS was 95.0% in the APBI group compared with 94.5% in the WBI group (P = .8). The 5-year overall survival rates were 97.3% in the APBI group compared with 95.6% in the WBI group (P = .1).
“The results of our study show that, at present, multicatheter brachytherapy is an attractive and viable APBI treatment option for low-risk breast cancer patients after breast-conserving surgery,” said study author Vratislav Strnad, MD, PhD, professor in the department of radiation oncology at University Hospital Erlangen, Germany and breast-chair of the GEC-ESTRO Brachytherapy Working Group, in a statement.
According to Strnad and colleagues, the study is the first to demonstrate the non-inferiority of APBI compared with WBI for a subgroup of early-stage breast cancer patients and the first large-scale prospective brachytherapy clinical study.
WBI is the standard radiation therapy for breast cancer, in which the entire breast is exposed to radiation over the course of several weeks. In the current study, APBI with multicatheter brachytherapy was delivered directly to the affected tissue rather than the whole breast and surrounding chest tissue.
APBI can reduce the exposure of the lungs, skin, and heart to radiation therapy. It is typically delivered 1 to 4 weeks following lumpectomy through the insertion of a catheter into the tissue that was placed during the lumpectomy procedure to eradicate any additional breast tumor cells that may remain following surgery. The typical radiotherapy course is about 8 to 10 days.
While many women are eligible for breast-conserving surgery followed by radiation therapy, a substantial proportion opt for a mastectomy in order to try to avoid WBI due to the relatively long course of treatment and potential harmful effects to surrounding organs.