Toxicity and clinical outcomes of partial breast irradiation (PBI) compared to whole breast irradiation (WBI) for early stage breast cancer: A systematic review and meta-analysis

Abstract

Background: There is uncertainty about efficacy and toxicity differences between adjuvant PBI and WBI in women with early-stage breast cancer treated with breast conservation. Methods: We identified randomized trials that compared PBI to WBI in early-stage invasive breast cancer using PubMed. Odds ratios (ORs), 95% confidence intervals (CI) and absolute risks were computed for pre-specified efficacy and toxicity outcomes including cosmetics. Subgroup analysis evaluated the effect of PBI modality (external beam radiation treatment [EBRT], intraoperative radiation treatment [IORT] or brachytherapy) on efficacy. Meta-regression analysis explored the influence of median follow- up as well as patients and tumor characteristics on results. Results: Eight trials comprising 10298 patients were included. Efficacy results, weighted absolute differences and subgroup analysis are shown in the table. PBI was associated with increased odds of local recurrence compared to WBI. However, PBI was associated with reduced odds of death without breast cancer recurrence and improved overall survival (OS). Subgroup analysis showed the effect on local recurrence was influenced by modality of radiation; odds of local recurrence were increased with IORT and brachytherapy, but not with EBRT. Nodal involvement was associated with higher local recurrence risk while larger tumors were associated with lesser improvement in death without breast cancer recurrence and OS. PBI was associated with higher odds of fat necrosis (p=0.002). Worse cosmetic outcome with PBI approached significance (p=0.06). Conclusions: Compared to WBI, PBI is associated with higher odds for local recurrence and toxicity, but less death without breast cancer recurrence and improved OS. The balance between benefit and risk of PBI appears optimal for women with smaller ER positive tumors and without nodal involvement. (Table Presented) .