Meta-Analysis of Local Invasive Breast Cancer Recurrence After Electron Intraoperative Radiotherapy

Background Electron intraoperative radiotherapy (IORT) can be used during breast conserving surgery to treat early-stage invasive breast cancer. Using data from current clinical and observational studies, this study aimed to assess the impact of single-fraction electron IORT on local recurrence rates. Methods Studies on single-fraction electron IORT during breast conserving surgery were identified through a search of PubMed and Google Scholar, as well as through secondary referencing. Local recurrence rate was the main outcome of interest. A meta-analysis of proportions using a binomial distribution to model the within-study variability and a random effects model was conducted to estimate a pooled local recurrence rate. To estimate a 5-year recurrence rate, a single-sample Poisson-normal model was applied to model the probability of events occurring during a fixed period (60 months). Results The study identified 13 publications. The analysis demonstrated a pooled monthly local recurrence rate of 0.02% per person-month (95% confidence interval CI 0.00–0.06%) for the studies with a follow-up period shorter than 5 years, 0.03% per person-month (95% CI 0.02–0.06%) for studies with a follow-up period of 5 years or longer, and 0.02% per person-month (95% CI 0.01–0.04%) overall. Based on this model, the predicted 5-year local recurrence rate was 2.7% (range 1.9–3.7%). Conclusions According to the published literature, the rate of breast cancer local recurrence after electron IORT was 0.02% per person-month, with an adjusted 5-year recurrence rate of 2.7%. These findings support the recent guidelines from the American Society for Radiation Oncology (ASTRO) supporting the use of electron IORT for low-risk patients.