Session Item

Comparative outcome data after intraoperative radiotherapy(IORT) and whole breast irradiation (WBI) for breast cancer at >10ys median follow-up are rare. We present a large, mature single-institution matched-pair comparison reporting survival and relapse rates in patients treated with either modality.

Complete datasets for 258 IORT patients treated between 2000 and 2010 were matched with 258 patients postoperatively treated with WBI by age/histology/tumor size, grading/lymph-node-status/hormone receptors/type of adjuvant therapy/surgical margins and treatment date. WBI was performed with 2 tangential fields to the whole breast (50Gy/25 fractions) and with a 9-12MeV direct-electron-field boost to the tumor bed (10-16Gy/5-8 fractions). IORT was performed on a non-dedicated Linac (green-line-setup) with direct 8-12MeV electron fields (21Gy prescribed to 90%-isodose). Relapse at surgical intervention site was classified as true local recurrence (LR). All recurrences in the treated breast (any quadrant) were classified as Ipsilateral Recurrence (IR).

Median follow-up was 157 months (12-251) for the IORT group, 154 months (31-246) for the WBI group. IR were 26 after IORT and 12 after WBI. LR for IORT and WBI groups were 16 and 6, respectively. Cumulative incidence of IR at 5, 10 and 15 years was 2.4%, 7.9% and 12.7% for IORT and 1.2%, 4.1% and 5.0% for WBI (p=0.02, HR 2.2 CI 95% 1.1-4.4). Cumulative incidence of LR at 5, 10 and 15 years was 1.6%, 5.1% and 8.3% for IORT and 0.4%, 2.1% and 2.5% for EBRT (p=0.02, HR 2.8 CI 95% 1.1-7.0). Overall survival (OS) at 5, 10 and 15 years was 96.9%, 91.7% and 78.9% for IORT and 96.1%, 90.2% and 76.6% for WBI (n.s.). Disease-free survival (DFS) at 5, 10 and 15 years was 95.3%, 89.5% and 74.6% for IORT and 94.1%, 86.6% and 75.0% for WBI (n.s.). No differences in non-breast-cancer-related deaths, second-cancer-incidence and cardiac events (arrhythmia or ischemic disease) were recorded in both treatment groups. When analyzed according to ASTRO-criteria for accelerated partial breast irradiation (APBI), outcome was better in the APBI-suitable group than in the entire cohort and the APBI-unsuitable group (IR/LR cumulative incidence at 5, 10 15 years of 0%/0%, 6.2%/3.3% and 7.3/3.3% for IORT and 0%/0%, 2%/2% and 3.1%/2% for WBI in “suitable” patients).

According with published randomized trial data, IR-rate was higher after IORT than after WBI if no stringent patient selection was performed. Second-cancer-incidence and cardiac events did not differ between IORT and WBI. In patients suitable for APBI according to ASTRO-criteria, similar IR-, LR- and OS-data indicate that IORT is a viable alternative to WBI.