Purpose: The increasing incidence of obesity throughout the world will result in expansion of the number of women at risk for developing breast cancer. Obesity is associated with adverse outcomes in postmenopausal women with breast cancer. In premenopausal women, the association is less clear. We investigated the impact of obesity on tumor features, hormonal status, recurrence and mortality in premenopausal breast cancer patients, classified according to molecular subtypes.
Methods: 818 premenopausal women with nonmetastatic breast cancer were analysed. Patients were classified into 3 groups according to body mass index (BMI): i) normal body weight (BMI: 18.5-24.9 kg/m(2)); ii) overweight (BMI: 25-29.9 kg/ m(2)); and iii) obese (BMI:>30 kg/ m(2)). Clinocopathologic characteristics and survival rates were analyzed for triple negative, HER-2 overexpressing and luminal subtypes.
Results: Obese patients compared with normal-weight women were older at diagnosis (p<0.001) and more often had high grade tumor (57.1 vs 42.3%; p=0.04) with lymphovascular invasion (79.5 vs 63.9%; p=0.03). The median follow-up period after diagnosis was 29 months. According to the molecular subtypes, overall survival (OS) and disease free survival (DFS) were significantly shorter in obese patients with triple negative breast cancer (TNBC) (p=0.001 and p=0.006, respectively). Obesity (HR 1.4; 95% CI 1.0-2.1; p=0.04) and lymphovascular invasion (HR 2.1; 95% CI 1.3- 3.3; p=0.02) were found to be independent prognostic factors for TNBC mortality.
Conclusion: Obesity is associated with estrogen (ER) and progesterone receptor (PR) negative tumors and poor OS in premenopausal women with breast cancer.