Single-center long-term follow-up after intraoperative radiotherapy as a boost during breast-conserving surgery using low-kilovoltage x-rays.

BACKGROUND: Intraoperative radiotherapy (IORT) during breast-conserving surgery as a boost followed by whole-breast radiotherapy is increasingly used.
METHODS: Between February 2002 and December 2008, a total of 197 patients were treated with IORT as a boost (20 Gy, 50 kV x-rays; Intrabeam System, Carl Zeiss Surgical, Oberkochen, Germany) during breast-conserving surgery, followed by whole-breast radiotherapy (46-50 Gy). Systemic therapy was provided according to the St. Gallen consensus. Patients were recalled every 6-12 months for follow-up. Findings were scored according to the LENT-SOMA scale.
RESULTS: Median age was 61.8 (range 30-84) years, and median follow-up was 37 (range 5-91) months. There were T1, T2, and Tx tumors in 129, 67, and 1 patients, respectively, and N0, N1, N2, and N3 disease in 144, 36, 15, and 2 patients, respectively. Until December 2009, 5 local invasive relapses, 1 local ductal carcinoma-in-situ, 1 axillary relapse, 6 secondary cancers, and 11 distant metastases were seen, resulting in a 5-year disease-free survival of 81.0% and an overall survival of 91.3%. Local relapse-free survival (invasive cancers) at 3 and 5 years was 97.0%. After a follow-up of 5 years (n =58), only 8 patients (13.8%) had chronic skin toxicities, and 2 patients (3.4%) had a marked increase in density (fibrosis III), while 62.0% had no/barely palpable fibrosis 0-I. Other toxicities observed included severe pain (n = 4, 6.9%), retraction (n =17, 29.3%), edema of the breast (n =1, 1.7%), and lymphedema in general (n =2, 3.4%).
CONCLUSIONS: After IORT as a tumor bed boost with low-kilovoltage x-rays followed by whole-breast radiotherapy, low local recurrence and chronic toxicity rates were seen after 5-year follow-up.