Objective: To study disease-free survival at 10 years in relation to obesity at the time of diagnosis.
Design: A prospective study of consecutively treated patients with primary breast cancer.
Setting: Memorial Sloan-Kettering Cancer Center, New York.
Patients: Nine hundred twenty-three women treated by mastectomy and axillary dissection.
Main results: Women who were obese (25% or more over optimal weight for height) at the time of primary breast cancer treatment were at significantly greater risk for recurrence (42%) compared with nonobese patients (32%) 10 years after diagnosis (P less than 0.01). In multivariate analyses, obesity remained a statistically significant prognostic factor after controlling for measured tumor size, number of positive axillary lymph nodes, age at diagnosis, and adjuvant chemotherapy with a hazard ratio of 1.29 (95% CI, 1.0 to 1.67). When analyses were restricted to the 557 patients free of lymph node metastases, the hazard ratio of recurrence associated with obesity was 1.59 (CI, 1.06 to 2.39); 32% of obese patients developed recurrent disease compared with 19% of nonobese women.
Conclusions: Obesity at the time of diagnosis is a significant prognostic factor that may limit the reduction in breast cancer mortality attainable through detection at an early stage of disease. Because obesity and the risk for breast cancer increase with age, interventions that encourage weight control may influence breast cancer survival rates.