Impact of obesity in postmenopausal early breast cancer patients receiving frontline adjuvant aromatase inhibitors.

Abstract

e11020 Background: Aromatase inhibitors (AIs), anastrozole (ANA) and letrozole (LET), have been shown to be more effective than tamoxifen in the adjuvant treatment of postmenopausal hormone receptor positive breast cancer. However, data from preclinical studies and subgroup analyses of some major clinical trials suggest differring efficacy among AIs. Yet the best clinical choice is still not very clear. This retrospective study aims at comparing the results of treatment with either AI among different subgroups of patients, especially among the obese patients. Methods: Between 2006-2011, 335 women with stage I to IIIC hormone receptor positive postmenopausal breast cancer treated with either ANA or LET as adjuvant treatment were included. Body mass index (BMI), estrogen and progesterone receptor (ER and PR) and HER-2 status at the time of diagnosis were recorded. Patients were grouped as BMI ≤ 30 and BMI > 30. The Kaplan-Meier survival estimates were calculated. Subgroups were compared with the log rank test. A 5 % type-I error was used to infer statistical significance. Results: The percentage of patients receiving ANA or LET were 47.2% and 57.8%, respectively. Median age at diagnosis was 58 (42-84) and lower in the ANA group (p=0.04). Stage II to IIIC disease was present in 76.8 % and the distribution was similar between ANA and LET (p=0.84). Median time of follow-up was 29 months (6-124) and median duration of hormonotherapy was 29 months (3-68) and similar between two groups (p=0.52 and p=0.55, respectively). Of the patients 41.2 % had a BMI of > 30. There was no significant difference in overall (OS) and progression-free (PFS) survivals between ANA and LET (p=0.08 and p=0.94, respectively). However, among patients with a BMI of > 30 a statistically insignificant benefit in PFS was observed with LET (p=0.1). ER, PR and HER2 status had no significant impact on OS and PFS. Conclusions: In a median follow-up of 29 months letrozole and anastrozole yielded similar OS and PFS. However, among patients with a BMI of > 30, LET might bring about a PFS advantage. In selected obese patients LET might be a reasonable choice in this setting. Larger studies with long term follow-up are needed to reach an exact conclusion.