['To investigate the risk factors and prognosis for locoregional recurrence (LRR) after breast conserving treatment (BCT) in women with early breast cancer.', 'Women who had undergone BCT from 1998 to 2005 at Chang Gung Memorial Hospital were retrospectively reviewed. LRR was defined as the reappearance of invasive carcinoma in the treated breast and/or ipsilateral axillary lymph node (ALN). The appearance of carcinoma outside this area was defined as distant metastasis (DM). Patient characteristics, tumor characteristics, treatment modality, and follow-up clinical evaluations were analyzed. Survival was estimated by the Kaplan-Meier method and compared with the log-rank test. A multivariate model was built by the Cox regression method.', 'This study included 858 patients, and the median follow up time was 36 (range 6-193) months. Twenty seven patients developed LRR for a crude LRR rate of 3.1%. The 5-year cumulative incidence of LRR was 5.0%. The mean age of patients at the primary operation was 45 (+/-9.8) years old. Their median body mass index (BMI) was 23 (range 16-40) kg/m(2). Univariate analysis of locoregional recurrence free survival (LRRFS) revealed that age < or =40 years, a low BMI (< or =24 kg/m(2)) and omission of postoperation radiotherapy were unfavorable factors. Low BMI and young age were independent prognostic factors for LRRFS in multivariate analysis. The five-year overall survival of patients with no recurrence, LRR and DM were 97.4%, 63.2% and 41.6%, respectively (p < 0.001).'] Is low body mass index an independent risk factor of locoregional recurrence in women with breast cancer undergoing breast conserving therapy?