Optimal radiotherapy after breast-conserving surgery for early breast cancer: A network meta-analysis of 23,418 patients

Purpose: In order to explore whether partial breast irradiation can replace hypofractionated whole breast irradiation and whether the former two are superior to conventional fractionated whole breast irradiation, we conducted a network meta-analysis based on the data from the latest randomized controlled trials to evaluate the efficacy of these radiotherapy modalities. Material and methods: Data from eligible studies were analyzed to determine the published events for ipsilateral breast tumor recurrence, distant metastasis, total deaths, and non-breast cancer-related deaths. In the case of low or high heterogeneity, the fixed-effect or random-effect model was used for statistical analysis respectively. NMA was performed by using the node-splitting model for two-category data among three radiotherapies based on a Bayesian method. Results: A total of 23,418 patients were included in 16 studies. For ipsilateral breast tumor recurrence, both pairwise (OR=1.9; CI95%: 1.2 -2.8; p<0.05) and indirect (OR=1.7; CI95%: 1.2 -2.4; p<0.05) comparison of three radiotherapies by network meta-analysis showed that conventional fractionated whole breast irradiation was significantly better than partial breast irradiation. Indirect comparison of three radiotherapies by network meta-analysis showed that hypofractionated whole breast irradiation was significantly better than partial breast irradiation (OR=1.6; CI95%: 1.0 -2.5; p<0.05). Network and paired meta-analyses found no significant differences in other endpoints among the three radiotherapies. Conclusion: Overall, this network meta-analysis showed that partial breast irradiation was related to the increase of ipsilateral breast tumor recurrence compared with hypofractionated or conventional fractionated whole breast irradiation in patients with early-stage breast cancer.