Association of Obesity with Breast Cancer Clinical and Pathological Factors: Analysis of Turkish National Breast Cancer Registry.

e12657 Background: Obesity is independently associated with breast cancer (BC) recurrence and poor prognosis despite therapy. However there is no data available about the effect of obesity on the natural course of BC in Turkish pts. This analysis focuses on the effect of obesity on the clinicopathological variables of BC. Methods: Pts presenting to medical oncology clinics were prospectively registered after October 2012 in 28 centers. Clinical and pathological characteristics were recorded. Patients were stratified according to body mass index (BMI): non-obese < 30 and obese ≥ 30.The association of BMI with patient demographics and pathologic characteristics were evaluated. Results: BMI of 13749 pts (128 males [0.9%]) were calculated. Obese pts with BMI ≥ 30 were older compared to non-obese pts (mean 51.7±11.7 vs 56.1±10.5 years; p < 0.001). There was no difference in gender in terms of obesity (p = 0.117). Obesity was more prevalent in postmenopausal pts compared to premenopausal women (64% vs 35.5%; p < 0.001). There was no difference in disease stage in obese vs non-obese patients (stage I 15.1% vs 18.5%; stage II 49.2% vs 48.6%; stage III 28% vs 24.6% and stage IV 7.7% vs 8.2%, respectively). Histopathological diagnosis of invasive ductal and lobular cancers were similar (p = 0.965), as well as tumor grades (grade 1: 8.9% vs 8.3%, grade 2: 46.1% vs 45.7%, and grade 3: 30.4% vs 30.3%, respectively) in obese and non-obese pts (p = 0.521). ER and PR status were similar in both groups. However, obese patients had a lower likelihood of Her2 positivity (25.5% vs 29.7%; p < 0.001). Obesity prevalence was not different among patients in BC molecular subgroups of luminal A/B, Her2-enriched and triple-negative (p = 0.186). Conclusions: This was the first large scale study investigating the relationship of obesity with BC clinical and pathological variables in Turkish pts. We showed that Her2 positivity was lower in obese patients. However, there was no association of obesity with ER/PR and BC molecular subtypes. Effect of BMI on patient outcomes will be analyzed separately.