Comparing long-term prognosis following different surgical methods in patients with early stage breast cancer and obesity: a retrospective cohort study in China

Objective Breast-conserving therapy (BCT) includes breast-conserving surgery (BCS) combined with radiation therapy (RT). RT plays a crucial role in improving the prognosis of patients who undergo BCS. However, obesity is a potential risk factor for resistance to radiation. The aim of this study was to evaluate any difference in the long-term prognosis of patients with early stage breast cancer and obesity treated with BCT or total mastectomy (TM).Design, setting and participants This was a retrospective cohort study involving 1125 patients diagnosed with early stage breast cancer and obesity at the Shanghai Cancer Center of Fudan University from 2013 to 2016.Outcome measures Obesity in the Chinese population was defined as a body mass index ≥28 kg/m2. Surgical options included BCT and TM. The primary survival outcomes were overall survival (OS), disease-free survival (DFS) and recurrence-free survival (RFS). Inverse probability of treatment weighting (IPTW) was used to control for the impact of confounding factors on prognosis.Results The median follow-up times in the BCT group and TM group without postoperative RT were 51.1 months (IQR of 40.6–68.1 months) and 61.8 months (IQR of 46.5–76.7 months), respectively. After IPTW, the baseline data were balanced. Compared with those in the TM cohort, patients in the whole IPTW cohort in the BCT cohort had worse DFS (HR 4.280, 95% CI 2.180 to 8.400; p