Increased body mass index (BMI) is known to be a strong risk factor for breast cancer in postmenopausal women. The purpose of this study was: 1) to determine the association between high BMI and diagnosis of either inflammatory breast cancer (IBC) or non-IBC-LABC; 2) to determine the prognostic value of high BMI in the overall cohort of LABC and in both subsets.
Patient and Methods
We retrospectively identified patients who had LABC (stage III) treated in prospective clinical trials at the M D Anderson Cancer Center between 1974 and 2000. BMI was divided into three groups: Group 1 < =24.9 (normal or underweight), Group 2 =< 25.0 - 29.9 (overweight), Group 3 >=30 (obese). Overall survival (OS) was calculated from start of treatment to death or last follow up. Recurrence-free survival (RFS) was calculated from start of treatment to date of recurrence or last follow up. Kaplan-Meier limit method was used to estimate survival outcomes. Cox proportional hazards were used to determine associations between survival and BMI and to test for an interaction between BMI and breast cancer type.
Nine hundred and thirteen patients were identified who had LABC of which 613 had available BMI data recorded at diagnosis and were included in the analyses. Five hundred and two (82%) had non IBC-LABC and 111 (18%) had IBC. Two hundred and eight patients (34%) were identified in group 1, 194 patients (32%) were in group 2, and 204 patients (34%) were in group 3. A higher incidence of patients with IBC were identified in group 3 compared to non IBC-LABC (p=0.01). Median follow-up among all patients was 6.1 years (range 0.1 - 30.6) and median follow-up among patients still alive at their last follow-up was 9.9 years (range 1.5 - 30.6). Median OS and RFS were 8.8 years and 5.9 years, respectively, for all patients. Overall, Groups 2 and 3 had worse OS and RFS than group 1 (p=0.001). In a univariate model group 2 and 3 non-IBC-LABC patients had worse OS and RFS than group 1. OS and RFS were similar for all three groups amongst IBC patients. In a multivariable model RFS was better for non-IBC-LABC than IBC patients (HR = 1.43, 95% CI 1.04-1.96, p=0.03) however, OS was not statistically different between the two types. There was no significant interaction between BMI and non-IBC-LABC/IBC. Ten year cumulative visceral recurrence rates for non IBC-LABC were 21%, 33%, 33% for groups 1, 2 and 3, respectively. Ten-year cumulative visceral recurrence rates for IBC was 18%, 51% and 30% for group 1, 2 and 3 respectively.
Patients with LABC and high BMI have a worse prognosis compared to those with low BMI. Furthermore, IBC is more frequently associated with obesity. The small number of patients may explain the lack of survival difference among the three groups in the IBC subset. A prospective assessment of serum markers of obesity, leptin and insulin like growth factors (IGF-1 and IGFP-3) in IBC is currently underway and preliminary data will be presented at the meeting.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA