Body mass index and breast cancer survival: a Mendelian randomization analysis

Qi Guo, Stephen Burgess, Constance Turman, Manjeet K Bolla, Qin Wang, Michael Lush, Jean Abraham, Kristiina Aittomäki, Irene L Andrulis, Carmel Apicella, Volker Arndt, Myrto Barrdahl, Javier Benitez, Christine D Berg, Carl Blomqvist, Stig E Bojesen, Bernardo Bonanni, Judith S Brand, Hermann Brenner, Annegien BroeksBarbara Burwinkel, Carlos Caldas, Daniele Campa, Federico Canzian, Jenny Chang-Claude, Stephen J Chanock, Suet-Feung Chin, Fergus J Couch, Angela Cox, Simon S Cross, Cezary Cybulski, Kamila Czene, Hatef Darabi, Peter Devilee, W Ryan Diver, Alison M Dunning, Helena M Earl, Diana M Eccles, Arif B Ekici, Mikael Eriksson, D Gareth Evans, Peter A Fasching, Jonine Figueroa, Dieter Flesch-Janys, Henrik Flyger, Susan M Gapstur, Mia M Gaudet, Graham G Giles, Gord Glendon, Mervi Grip, kConFab/AOCS Investigators, Ian Tomlinson

Research output: Contribution to journalArticlepeer-review

Abstract

Background: There is increasing evidence that elevated body mass index (BMI) is associated with reduced survival for women with breast cancer. However, the underlying reasons remain unclear. We conducted a Mendelian randomization analysis to investigate a possible causal role of BMI in survival from breast cancer.

Methods: We used individual-level data from six large breast cancer case-cohorts including a total of 36 210 individuals (2475 events) of European ancestry. We created a BMI genetic risk score (GRS) based on genotypes at 94 known BMI-associated genetic variants. Association between the BMI genetic score and breast cancer survival was analysed by Cox regression for each study separately. Study-specific hazard ratios were pooled using fixed-effect meta-analysis.

Results: BMI genetic score was found to be associated with reduced breast cancer-specific survival for estrogen receptor (ER)-positive cases [hazard ratio (HR) = 1.11, per one-unit increment of GRS, 95% confidence interval (CI) 1.01-1.22, P = 0.03). We observed no association for ER-negative cases (HR = 1.00, per one-unit increment of GRS, 95% CI 0.89-1.13, P = 0.95).

Conclusions: Our findings suggest a causal effect of increased BMI on reduced breast cancer survival for ER-positive breast cancer. There is no evidence of a causal effect of higher BMI on survival for ER-negative breast cancer cases.

Original languageEnglish
Pages (from-to)1814-1822
Number of pages9
JournalInternational Journal of Epidemiology
Volume46
Issue number6
Early online date9 Oct 2017
DOIs
Publication statusPublished - 1 Dec 2017

Keywords

  • Journal Article

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