Intraoperative radiotherapy given as a boost after breast-conserving surgery in breast cancer patients

Abstract

Conventional radiotherapy after breast-conserving therapy is confined to 50–55 Gy external beam radiation therapy (EBRT) to the whole breast and 10–16 Gy external boost radiation to the tumour bed or brachytherapy to the tumour bed. Local recurrence rate after breast-conserving surgery varies between 5 and 18%. External boost radiation can partially miss the tumour bed and therefore can result in local failure. Intra-operative radiotherapy (IORT) as a high precision boost can prevent a ‘geographical miss’. From October 1998 to December 2000, 156 patients with stage I and stage II breast cancer were operated upon in a dedicated IORT facility. After local excision of the tumour, the tumour bed was temporarily approximated by sutures to bring the tissue in the radiation planning target volume. A single dose of 9 Gy was applied to the 90% reference isodose with energies ranging from 4 to 15 MeV, using round applicator tubes 4–8 cm in diameter. After wound healing, the patients received additional 51–56 Gy EBRT to the whole breast. No acute complications associated with IORT were observed. In 5 patients, a secondary mastectomy had to be performed because of tumour multicentricity in the final pathological report or excessive intraductal component. 2 patients developed rib necroses. In 7 patients, wound healing problems occurred. After a mean follow-up of 18 months, no local recurrences were observed. Cosmesis of the breast was very good and comparable to patients without IORT. Preliminary data suggest that IORT given as a boost after breast-conserving surgery could be a reliable alternative to conventional postoperative fractionated boost radiation by accurate dose delivery and avoiding geographical misses, by enabling smaller treatment volumes and complete skin-sparing and by reducing postoperative radiation time by 7–14 days.