The tumor-to-breast volume ratio (TBR) predicts cancer-specific survival in breast cancer patients who underwent modified radical mastectomy.

Breast cancer is the most common cancer in women globally, and tumor size measured as the largest diameter of the tumor focus is currently used in tumor-lymph node-metastasis (TNM) staging for prognosis and treatment decisions. The present study utilized the tumor-to-breast volume ratio (TBR) to evaluate the relative tumor size and determined the prognostic impact of TBR on survival in patients with breast cancer. Two thousand twenty-five consecutive breast cancer patients who underwent modified radical mastectomy between January 2002 and December 2008 at Sun Yat-Sen University Cancer Center were enrolled in this retrospective study. Kaplan-Meier analysis was used to assess the prognostic effect of TBR on cancer-specific survival (CSS), and univariate log-rank test and multivariate Cox proportional hazards regression model were performed to identify independent prognostic factors. The optimal cutoff value of TBR was determined to be 1.70 %, and 1473 and 552 patients were categorized to low-TBR and high-TBR groups, respectively. In the whole patient cohort, CSS was significantly shorter in the high-TBR group (110.2 vs 128.5 months, P < 0.001). Univariate and multivariate analyses revealed that TBR was an independent prognostic factor of CSS in breast cancer patients (hazard ratio (HR) 1.489, 95 % CI 1.130-1.961, P = 0.005). High TBR was independently associated with poor prognosis in breast cancer patients. This variable may serve as a valuable parameter to predict the outcomes of breast cancer.