Abstract P1-12-11: Prospective study of aromatase inhibitor-induced bone loss and lipid levels in early hormone sensitive breast cancer treated with AI during 8 years

Abstract

Abstract Introduction: AI’s are the preferred adjuvant hormonal treatment for postmenopausal(PM) estrogen receptor positive (ER+) disease because of the improved efficacy over tamoxifen in terms of disease free survival and reduction in distant recurrence. AI’s have been associated with increased bone loss by blocking peripheral tissue estrogen synthesis, arthralgia and a negative effect on lipid metabolism. In this prospective study we wanted to assess the amount of bone loss and the changes in lipid levels in early breast cancer(EBC) patients (pts) treated with 3yrs of extended letrozole as part of the SOLE study after 5 yrs of adjuvant AI. Objectives: the primary objective of the study is to calculate the mean percentage change in bone mineral density(BMD)(g/cm2) after 8 yrs of letrozole and to compare between the continuous(C) and intermittent(I) intake of letrozole. The secondary objectives are to correlate the mean change in BMD with the initial value, BMI and to describe the evolution of the lipid levels in both groups. Patients and methods: BMD was measured at the lumbar spine (L2-4) and hip by dual energy X-ray absorptiometry (DEXA) in PM pts. with ER+ EBC. We also measured the fasting lipid levels baseline and after 8 yrs of an AI. Differences between the two groups were assessed by the independent samples T-test and the correlation by the linear regression analysis. Results: Fifty four pts were included in the study with a mean age of 62.5 yrs(+/-8.6 yrs). Seventeen pts are too early to be evaluable, 8 pts stopped letrozole due to adverse events and 2 pts had no baseline DEXA values. Two pts received tamoxifen 2 to 5 yrs before inclusion in the SOLE study. The remaining 25 pts showed a mean change in BMD for the lumbar spine of -1.1 (10.6SD) and for the hip -4.4 (7.04SD). Currently 13 pts in the C arm demonstrated a mean decrease in BMD for the (LS) of -2.7(10.2SD), and for the hip of -2.7(5.5SD). Twelve pts included in the I arm experienced a mean increase in BMD for the LS of 0.65(SD11.2) and a mean decrease in BMD for the hip of -4.9(9.1SD). The difference between the two treatment groups was not significant for the LS measurements after 8yrs (p=0.4) nor for the hip (p=0.23) neither was it at baseline (p=0.9; 0.1). Only three pts had fractures due to trauma. The overall fracture rate was only 0.05%.There was no correlation with the BMI, but there was a significant correlation with baseline BMD.(p=0.002)The mean fasting cholesterol levels at 8yrs in the C arm was 214mg/dl(41.3SD) and in the I arm was 218mg/dl(35.6SD)and was not significantly different(p=0.8), nor was it at baseline(p=0.5). Conclusion: This first prospective long term BMD and lipid follow-up study in PM EBC pts taking adjuvant letrozole beyond 5 yrs shows a decline in BMD. Until now no significant differences were observed between continuous and intermittent letrozole. An updated and detailed follow-up on more patients will be presented. Citation Format: Christel Fontaine, Lore Decoster, Denis Schallier, Leen Vanacker, Jacques De Grève, Marian Vanhoeij, Guy Verfaillie, Jan Lamote. Prospective study of aromatase inhibitor-induced bone loss and lipid levels in early hormone sensitive breast cancer treated with AI during 8 years [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-12-11.