Long-term Efficacy and Cosmetic Outcomes of Partial-breast Irradiation Using Multicatheter Interstitial Brachytherapy for Breast-conserving Therapy

Abstract

Purpose : Partial-breast irradiation (PBI) is an alternative to whole-breast irradiation (WBI) for breast-conserving therapy. Although several randomized controlled trials demonstrated that PBI showed an equivalent efficacy to WBI, limited data are available for Japanese patients. This study was made to clarify the usefulness of PBI.

Methods : Patients aged ≥40 years, with a maximum tumor diameter of ≤3.0 cm, and with sentinel nodes negative for metastases underwent PBI using multicatheter interstitial brachytherapy (MIB) delivering 32 Gy in 8 fractions. Oncological and cosmetic outcomes were evaluated.

Results : Between 2008 and 2020, a total of 657 patients underwent MIB-PBI. The median age and follow-up time were 57 years and 6.1 years, respectively. Ipsilateral breast tumor recurrence (IBTR) was observed in 23 patients (3.5%). The 5-year cumulating incidence of IBTR, relapse-free interval, and overall survival were 2.2%, 96.6%, and 99.7%, respectively. Cosmetic results could be assessed in 172 patients with a minimum follow-up period of 5 years, and excellent or good outcomes with the Harvard cosmesis score and the Breast Cancer Conservative Treatment cosmetic results (BCCT.core) software were observed in 155 patients (90.1%) and 143 patients (83.1%), respectively.

Conclusions : Although this study was a retrospective registry trial from a single institution, MIB-PBI had an acceptable clinical efficacy for local control and long-term cosmetic outcomes in Japanese patients.