Feasibility of breast preserving therapy with single fraction in situ radiotherapy delivered intraoperatively.

Background: Accelerated partial breast irradiation (APBI) has gained widespread interest as a means of improving the convenience and availability of breast conserving radiotherapy. Intraoperative radiation therapy (IORT) is an APBI technique that delivers breast radiotherapy as a single dose at the time of partial mastectomy. We adapted the technique of Veronesi to deliver IORT prior to tumor excision to improve delivery to the region at risk and reduce the volume of normal tissue irradiated.
Methods: Patients age >or=55 with ultrasonographically defined tumors <or=3 cm and invasive ductal carcinoma confirmed by core biopsy were eligible. Pre-operative ultrasound was performed at the time of needle localization and radiocolloid injection. IORT treatment planning was performed prior to surgery using ultrasound tumor definition, selecting cone size and electron energy to optimize dose distribution. In the operating room, the surgeon retracted the skin over the tumor, cone was placed and radiotherapy delivered. Standard partial mastectomy was then performed.
Results: Twenty-three patients were enrolled in the study. Eighteen patients completed IORT with 10 patients having successful IORT no additional local therapy necessary. In five patients, the intraoperative radiation therapy served as the boost and in three patients unsuspected larger tumors or multicentric disease necessitated a mastectomy. The majority of patients had a good to excellent cosmetic result.
Conclusions: Single fraction in situ IORT prior to partial mastectomy is feasible for patients with small breast cancers in achieving a good to excellent cosmetic result. Based on this early preliminary data, we plan to expand our feasibility trial.