Three-Fraction Accelerated Partial Breast Irradiation (APBI) Delivered With Brachytherapy Applicators Is Feasible and Safe: First Results From the TRIUMPH-T Trial

Abstract

Shorter courses of accelerated partial-breast irradiation delivered as single-fraction intraoperative therapy are now offered as an alternative to 4 to 6weeks of whole-breast irradiation after lumpectomy. However, this approach has potential shortcomings in patient selection and target volume definition and in dosimetric, radiobiological, and logistical issues. We designed a prospective, phase 2, multi-institution clinical trial to study 2- or 3-day accelerated partial breast irradiation delivered with brachytherapy applicators. This trial treats select breast cancers after breast-conserving surgery with brachytherapy applicators that deliver 22.5Gy in 3 fractions of 7.5Gy. The planning treatment volume was 1 to 1.5cm beyond the surgical cavity. Eligible women were aged ≥45years with unicentric invasive or in situ tumors ≤3.0cm with positive estrogen or progesterone receptors and no metastasis to axillary nodes that have been excised with negative margins. Strict dosimetric parameters were required to be met before acceptance into the trial. A group of 200 patients was prospectively enrolled and followed for a minimum of 6months. Two- or 3-day brachytherapy was associated with low acute or subacute toxicity, 97.25% excellent or good cosmetic outcomes, and excellent local control in select breast cancers. Ultrashort breast brachytherapy is dosimetrically feasible and can be delivered with excellent short-term tolerance and low toxicity.