Eligibility criteria for intraoperative radiotherapy for breast cancer: study employing 12,025 patients treated in two cohorts.

BACKGROUND: We wished to estimate the proportion of patients with breast cancer eligible for an exclusive targeted intraoperative radiotherapy (TARGIT) and to evaluate their survival without local recurrence.

METHODS: We undertook a retrospective study examining two cohorts. The first cohort was multicentric (G3S) and contained 7580 patients. The second cohort was monocentric (cohort 2) comprising 4445 patients. All patients underwent conservative surgery followed by external radiotherapy for invasive breast cancer (T0-T3, N0-N1) between 1980 and 2005. Within each cohort, two groups were isolated according to the inclusion criteria of the TARGIT A study (T group) and RIOP trial (R group).In the multicentric cohort (G3S) eligible patients for TARGIT A and RIOP trials were T1E and R1E subgroups, respectively. In cohort number 2, the corresponding subgroups were T2E and R2E. Similarly, non-eligible patients were T1nE, R1nE and T2nE, and R2nE.The eligible groups in the TARGIT A study that were not eligible in the RIOP trial (TE-RE) were also studied. The proportion of patients eligible for TARGIT was calculated according to the criteria of each study. A comparison was made of the 5-year survival without local or locoregional recurrence between the TE versus TnE, RE versus RnE, and RE versus (TE-RE) groups.

RESULTS: In G3S and cohort 2, the proportion of patients eligible for TARGIT was, respectively, 53.2% and 33.9% according the criteria of the TARGIT A study, and 21% and 8% according the criteria of the RIOP trial. Survival without five-year locoregional recurrence was significantly different between T1E and T1nE groups (97.6% versus 97% [log rank=0.009]), R1E and R1nE groups (98% versus 97.1% [log rank=0.011]), T2E and T2nE groups (96.6% versus 93.1% [log rank<0. 0001]) and R2E and R2nE groups (98.6% versus 94% [log rank=0.001]). In both cohorts, no significant difference was found between RE and (TE-RE) groups.

CONCLUSIONS: Almost 50% of T0-2 N0 patients could be eligible for TARGIT.