Combined effects of hormone therapy, alcohol consumption and body mass index in relation to postmenopausal breast cancer

Hvidtfeldt, Ulla

Combined effects of hormone therapy, alcohol consumption and body mass index in relation to postmenopausal breast cancer

Wednesday, 20 August 2014: 4:45 PM

Summit Hall, Egan Center Room 3 (Dena'ina Center)

Ulla A Hvidtfeldt, MPH , University of Copenhagen, Copenhagen, Denmark

Anne Tjønneland, PhD , Danish Cancer Society Research Center, Copenhagen, Denmark

Niels Keiding, PhD , University of Copenhagen, Copenhagen, Denmark

Theis Lange, PhD , University of Copenhagen, Copenhagen, Denmark

Ingelise Andersen, PhD , University of Copenhagen, Copenhagen, Denmark

Thorkild Sørensen, PhD , University of Copenhagen, Copenhagen, Denmark

Eva Prescott, PhD , Bispebjerg and Frederiksberg Hospitals, The Capital Region, Copenhagen, Denmark

Åse Marie Hansen, PhD , National Research Centre for the Woking Environment, Copenhagen, Denmark

Morten Grønbæk, PhD , University of Southern Denmark, Copenhagen, Denmark

Stig E Bojesen, PhD , Herlev Hospital, Copenhagen University Hospital, Herlev, Denmark

Finn Diderichsen, PhD , University of Copenhagen, Copenhagen, Denmark

Naja H Rod, PhD , University of Copenhagen, Copenhagen, Denmark

INTRODUCTION: Combined effects of Alcohol consumption, increased body mass index (BMI) and hormone therapy (HT) on postmenopausal breast cancer (BC) are not well understood – but important in order to identify potential “low-risk” users of HT. We investigated interactions as departure from additivity between these risk factors on risk of all BC and according to estrogen receptor (ER) status.

METHODS: Two prospective cohorts were pooled including 30,789 women aged 50+ years. Stratified and joint analyses were performed in adjusted additive hazards models. Joint associations between HT/high BMI and HT/alcohol consumption and serum levels of estradiol and testosterone were estimated in a subsample of approximately 1,000 women.

RESULTS: During 392,938 person-years (pyrs) of follow-up, 1,579 developed BC. In HT non-users, overweight vs. normal weight was associated with 54 (95% CI: 6; 102) additional BC cases per 100,000 pyrs. In contrast, the equivalent estimate in current HT users was -121 (95% CI: -216; -26), p for interaction=0.003. In the joint analyses with normal weight HT non-users as the reference category, the risk of BC was higher in HT users across all BMI-strata. A weekly alcohol consumption of >7 drinks vs. abstinence was associated with 72 (95% CI: 12; 131) additional cases per 100,000 pyrs, whereas the equivalent estimate in HT users was 180 (95% CI: 42; 319), p for interaction=0.02. Thus, a markedly higher risk of BC was observed for alcohol combined with HT use compared to abstinent non-users. The effects of HT, high BMI and alcohol consumption were primarily restricted to ER-positive cases. Combined effects of HT/high BMI and HT/alcohol on serum estradiol and testosterone supported the hypothesis of a hormonal pathway linking these exposures to BC.

CONCLUSIONS: These analyses suggest caution when prescribing HT in general, and especially to women consuming alcohol. Results for HT combined with BMI were inconclusive.