Six-year outcome of a prospective study evaluating tumor bed boost with intra-operative electron irradiation followed by whole-breast irradiation for early-stage breast cancer.

A prospective study was performed for patients with early-stage breast cancer in which a single fraction of intraoperative electron irradiation (IOERT) was given to the tumor bed, followed by conventional fractionated whole-breast irradiation (WBRT). Patients with T1/T2N0 breast cancer underwent lumpectomy and sentinel lymph node biopsy. A tumor bed boost of 10 Gy of IOERT using 6-12 MeV electrons was administered by a dedicated mobile linear accelerator in the operating room. After adequate wound healing, 48 Gy WBRT was given to the whole breast in 24 fractions. Fifty-two patients were enrolled between February 2003 and January 2005. At a median follow-up of 79 months, there were two local relapses. The 6-year actuarial overall survival and distant control rates were 89% and 96%, respectively. At last follow-up, cosmesis was graded as excellent or good in 45 (87%), fair in five (10%), and poor in two patients (4%), respectively. Difficulty in wound healing occurred in two patients who had additional surgery later. One patient developed significant fibrosis after aspiration of a symptomatic seroma. The result of this pilot study shows the feasibility of using IOERT as the tumor bed boost in lieu of 6-8 days of standard electron beam treatment with good local control and cosmetic results. However, late surgical intervention of the lumpectomy bed may result in more pronounced tissue fibrosis and wound healing difficulty.