Accelerated partial-breast irradiation (APBI) using multicatheter brachytherapy after breast-conserving surgery is as effective as whole-breast irradiation for low-risk patients, according to research presented at this week's American Society for Radiation Oncology (ASTRO) meeting.
Five-year follow-up demonstrated equivalent local control, disease-free, and overall survival rates between the two techniques, concluded the group led by Dr. Vratislav Strnad, PhD, from University Hospital Erlangen in Germany.
The phase III study was conducted from April 2004 to July 2009 across 16 centers throughout Europe. The trial included 1,184 patients ages 40 or older with early-stage breast cancer (0, I, and IIA) who received breast-conserving surgery. The patients were then randomly assigned to receive conventional treatment, consisting of 50-Gy whole-breast irradiation with a tumor bed boost of 10 Gy for approximately seven weeks, or APBI using interstitial multicatheter brachytherapy for five days.
The median follow-up of patients was 6.6 years, and baseline factors were evenly distributed across the study arms. The primary end point was local recurrence. Secondary end points were incidence and severity of acute and late side effects, cosmesis, cumulative incidence of lymph node metastases and distant metastasis, overall survival, and disease-free survival.
Long-term follow-up demonstrated that for the selected low-risk patients, APBI yielded equivalent local control, disease-free survival, and overall survival, compared with conventional whole-breast irradiation. In the APBI group, five-year local recurrence was 1.4%, five-year disease-free survival was 95%, and five-year overall survival was 97.3%.
By contrast, the whole-breast irradiation group showed a five-year local recurrence rate of 0.9%, five-year disease-free survival of 94.5%, and five-year overall survival of 95.6%. The equivalence of local recurrence rates was evident in all age groups and for all tumor types, independent of additional drug therapy (e.g., chemotherapy, antihormonal therapy), the researchers found.
The favorable results are in contrast with the disappointing and controversial results reported from other studies that used other APBI techniques, such as intraoperative and external-beam radiation therapy, according to the group.
Further research and analyses will need to be conducted to determine recurrence rates among different age subgroups at follow-up beyond five years, the researchers added.
