A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using interstitial brachytherapy: clinical results with a median follow-up of 26 months

A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using interstitial brachytherapy was performed. The first clinical results were reported with a median follow-up of 26 months. Forty-six female breast cancer patients with positive hormone receptors and tumors ≤3 cm, pN0M0, completed the protocol treatment. After breast-conserving surgery and histological confirmation of negative surgical margins and pN0, brachytherapy applicators were implanted either postoperatively (n = 45) or intraoperatively (n = 1). High-dose-rate brachytherapy of 36 Gy/6 fractions was delivered. All clinical data were prospectively collected using case report forms and the Common Terminology Criteria for Adverse Events ver.3.0. At the median follow-up of 26 months, no breast cancer recurrence of any type was observed. Sequelae ≥G2 were dermatitis (G2, 7 %), fibrosis (G2, 11 %; G3, 4 %), fracture (G2, 2 %), pain (G2, 7 %; G3, 2 %), and soft tissue necrosis (G2, 6 %). Cosmetic outcomes evaluated by excellent/good scores were 100 % at pre-therapy (n = 46), 94 % at 12 months (n = 46), and 81 % at 24 months (n = 36), respectively. Disease control and sequelae were satisfactory due to the strict eligibility and protocol-defined treatment parameters. The cosmetic outcomes were comparable to those of previous Japanese breast-conserving therapy series.