Abstract PD09-07: Breast Cancer Patients with WHO Class II Obesity or Greater (BMI ≥35) Have Poorer Overall Survival after Receiving Chemotherapy Compared to Similar Patients with Lower Body Mass Index

Abstract

Background: Breast cancer (BCa) is the most common non-cutaneous malignancy and the second leading cause of cancer-related mortality among US women. Obesity has commonly been associated with increased risk for malignancy. There have been few studies looking at the effect of obesity on prognosis in BCa patients receiving chemotherapy (ctx). This retrospective study, conducted at the Medical College of Georgia utilizing tumor registry data, assesses the correlation between body mass index (BMI) and overall survival (OS) in BCa patients receiving ctx. Methods: Data were obtained from the MCG Tumor Registry (Augusta, GA). Inclusion criteria were all BCa patients receiving ctx between 1997 and 2006. The estimated hazard ratio (HR) from Cox regression was used to measure the association between BMI and OS among these patients. Race, age at diagnosis, stage at diagnosis, and body surface area were considered for inclusion as covariates in the regression model. Results: Data on height and weight from the first day of ctx were collected for a sample of 259 women who received ctx for breast cancer. BMI values were calculated based on these data and categorized using WHO BMI classification parameters. The initial analysis examined women with BMI ≥25 (WHO criteria of overweight or more), which classified 186 women (71.8%) as overweight or more and 73 women (28.2%) as under/normal weight. This analysis did not yield a significant association with OS (unadjusted HR, 1.12; 95% CI, 0.69-1.82; p = 0.652). The next analysis examined women with BMI ≥30 (WHO criteria of class I obesity or more), which classified 115 women (44.4%) as class I obese or more and 144 (55.6%) as non-obese. This cut off demonstrated a decreased OS for the obese patients, but the results were not statistically significant (unadjusted HR, 1.10; 95% CI, 0.72-1.69; p = 0.650). The final analysis examined women with BMI ≥35 (WHO criteria of class II obesity or more); this yielded 67 women (25.9%) classified as class II obese or more and 192 women (74.1%) classified as less than class II obese. This analysis demonstrated a decreased OS for class II obese or more patients (unadjusted HR, 1.56; 95% CI, 1.00-2.43; p = 0.049). The only other factor that was significantly associated with OS was stage at diagnosis. When the HR for class II obese or more patients was adjusted for stage, statistical significance was retained (HR, 1.57; 95% CI, 1.00-2.44; p = 0.048). Discussion: Women with BCa treated with ctx who are WHO class II obese (BMI ≥35) or more have significantly lower overall survival than women with BMI < 35 regardless of race or age at diagnosis. The statistical significance for OS was also retained when adjusted for stage. A primary limitation of our study was a small sample size. Adjustments to ctx dosing in patients with BMI ≥35 may also affect survival outcomes. Future studies will examine the effect of the type and dosing of ctx regimens used, comorbidities, and actual cause of death in this cohort of patients. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD09-07.