Impact of Obesity on Breast Cancer

Background: Obesity is linked with a high risk of breast cancer and affects prognosis as it is correlated with different molecular subtypes. Method: All breast cancer patients referred to Kasr Alainy Oncology Center of Clinical Oncology and Nuclear Medicine (NEMROCK) from 2004 to2014 were recruited in this retrospective study. They were divided into three groups according to body mass index (BMI): non-obese (BMI < 30), obese (BMI= 30-34.9) and severely obese (BMI ≥ 35). Results: There were 950 breast cancer patients with a median follow-up of 4.2 years. The mean age was 50.1 years, and BMI was assessed in 760 cases. Obesity was observed in 63.29% of the cases (23.82% obese and 39.47% severely obese). There was a statistically significant difference between non-obese and severely obese patients as regards age (52 vs. 48 years, P < 0.001), menopausal status (31.3 vs. 46.9%, P < 0.001), molecular types (non- luminal; 25 vs. 50%, P < 0.011), Her2 status (44.4 vs. 27.2%, P = 0.014), and hormonal therapy (Tamoxifen alone, 44.3 vs. 30.4%, P = 0.001). High BMI >30 had a worse mean overall survival (OS) (80, 88, and 102.5 months in obese, severely obese, and non-obese patients, respectively, P=0.019); however, this did not affect the disease-free survival (P = 0.40). In multivariate analysis, the factors that also had a significant effect on OS were lymph node stage (P <0.001; odds ratio (OR): 1; 95% confidence interval (CI): 0.07-0.46), BMI (P = 0.001; odds ratio (OR): 1; 95% CI: 0.14-0.61), and hormonal treatment (tamoxifen alone, P = 0.001; OR: 1; 95% CI: 1.4-16.4). Conclusion: Severe obesity (BMI >35) had a poor OS with no influence on disease-free survival.