Abstract P6-09-07: Obesity; Not Associated with Risk of Second Malignancy in Early Stage Breast Cancer

Introduction: Early diagnosis and effective local and systemic therapy has reduced the risk of relapse and death from breast cancer; thus, patients are living longer but experience an increased risk for the development of a second malignancy (SM). Risk factors for SM may be genetic, related to environmental or behavioral factors or to breast cancer treatments such as radiotherapy, chemotherapy or hormone therapy. Controversy exists over the role of obesity and breast cancer outcomes, and there is little information on long term survivors. LSUHSC Shreveport provides care for a predominantly indigent population with high rates of obesity. This allows us to study the role of obesity and risk of SM after breast cancer diagnosis. In this study, we sought to determine the incidence and risk factors for SM in women after treatment for early stage breast cancer. Methods: We performed a retrospective analysis of all patients treated for invasive breast cancer from 1980 through 2006 at LSUHSC Shreveport. Patients with stage IV at diagnosis were excluded. Second malignancy was defined as a new diagnosis of primary malignancy at least three months after initial breast cancer diagnosis. We reviewed the demographics, smoking status, BMI at diagnosis of breast cancer, tumor characteristics, breast cancer treatments (surgery, radiotherapy, chemotherapy and hormonal therapy) and site and date of second malignancies. Descriptive statisticswere performed to characterize the group of patients who developed a SM and Cox proportional hazard regression model was used to estimate the relative risk of development of SM. Results: Of the 1214 patients analyzed, 118 (9.72%) patients developed a SM: 54% (n=64) breast cancer, 12.7% (n=15) gynecologic cancer, 8.5% (n=10) GI malignancy, 6.8% (n= 8) lung cancer, 6.8% (n=8) hematologic malignancy and 11% (n=13) various miscellaneous cancers. The median time for the development of SM was 7.6 years. The risk for development of SM increased with longer follow up: the risk at 5 years after breast cancer diagnosis was 2.3%, at 10 years was 10% and at 20 years was 30%. Patients with SM in comparison with patients without it were more likely to be obese (57%, p=0.05) and to have received radiotherapy (60%, p=0.01). No differences were observed with age at diagnosis, race, smoking status, use of chemotherapy, ER status, or use of hormone therapy. In a multivariate analysis using the Cox regression model, after adjusting for race, age, smoking status, use of chemotherapy and ER status, radiotherapy was a significant predictor of SM (HR=2.8, p=0.01). Obesity was not associated with an increased risk of SM (HR=0.91, p=0.82). Conclusions: Our study has some limitations typical of retrospective studies and the generalization of the results may be limited. We found that obesity at diagnosis of breast cancer did not adversely affect the rate of SM while radiotherapy represents a significant risk factor. Further studies are needed to define the role of lifestyle and cancer treatments on develop of SM in patients with early stage breast cancer. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-09-07.