Efficacy of Single-Plane Implant Technique in Partial Breast Brachytherapy in Small-Breasted Patients

Partial-breast irradiation (PBI) using multicatheter-interstitial brachytherapy (MIB) has been supported by some randomized trials to date. However, it remains underused in Asian countries because of the population's typically smaller breasts. Single-plane implantation has been recommended in these individuals, but limited data on the clinical efficacy exist. We performed a retrospective chart review to compare the tumor control and long-term cosmesis in patients treated with the single-plane implant technique.

Patients receiving MIB-PBI between October 2008 and December 2018 were evaluated. PBI was initiated on the same day of the surgery via an intraoperative catheter implant, delivering 32 Gy by 8 fractions. Tumor control based on the rate of freedom from ipsilateral tumor recurrence (IBTR), disease-free survival, and long-term cosmesis using the Harvard scale was evaluated to compare between the single- and double-/triple-plane implant techniques.

Five hundred sixteen patients with 526 lesions received MIB-PBI with a median follow-up of 53.1 months. Patients treated by single- and double- or triple-plane implant numbered 288 (54.8%) and 238 (45.2%), respectively. The 4-year probabilities of IBTR-free survival and disease-free survival were 97.5% and 96.5% in single-plane implant and 98.6% (P = .42) and 98.0% (P = .18) in double- or triple-plane implant MIB-PBI, respectively. Although young age (P < .05) and positive surgical margins (P < .01) were selected as independent risk factors for IBTR, single-plane implantation was not recognized as a risk factor of IBTR. Sixty-one of 69 single-plane implant patients (88.4%) and 84 of 92 double-/triple-plane implant patients (91.3%) reported excellent to good cosmetic results (P = .73).

Although this was a retrospective study from a single institution and cosmesis was evaluated using a subjective method, this is the first report to validate single-plane implant MIB-PBI for use in small-breasted patients. Further multicenter research is required.