Guo, QiBurgess, StephenTurman, ConstanceBolla, Manjeet KWang, QinLush, MichaelAbraham, JeanAittomäki, KristiinaAndrulis, Irene LApicella, CarmelArndt, VolkerBarrdahl, MyrtoBenitez, JavierBerg, Christine DBlomqvist, CarlBojesen, Stig EBonanni, BernardoBrand, Judith SBrenner, HermannBroeks, AnnegienBurwinkel, BarbaraCaldas, CarlosCampa, DanieleCanzian, FedericoChang-Claude, JennyChanock, Stephen JChin, Suet-FeungCouch, Fergus JCox, AngelaCross, Simon SCybulski, CezaryCzene, KamilaDarabi, HatefDevilee, PeterDiver, W RyanDunning, Alison MEarl, Helena MEccles, Diana MEkici, Arif BEriksson, MikaelEvans, D GarethFasching, Peter AFigueroa, JonineFlesch-Janys, DieterFlyger, HenrikGapstur, Susan MGaudet, Mia MGiles, Graham GGlendon, GordGrip, MerviGronwald, JacekHaeberle, LotharHaiman, Christopher AHall, PerHamann, UteHankinson, SusanHartikainen, Jaana MHein, AlexanderHiller, LouiseHogervorst, Frans BHolleczek, BerndHooning, Maartje JHoover, Robert NHumphreys, KeithHunter, DavidHüsing, AnikaJakubowska, AnnaJukkola-Vuorinen, ArjaKaaks, RudolfKabisch, MariaKataja, VesaKnight, Julia AKoppert, Linetta BKosma, Veli-MattiKristensen, Vessela NLambrechts, DietherLe Marchand, LoicLi, JingmeiLindblom, AnnikaLindström, SaraLissowska, JolantaLubinski, JanMachiela, Mitchell JMannermaa, ArtoManoukian, SiranoushMargolin, SaraMarme, FederikMartens, John WMMcLean, CatrionaMenéndez, PrimitivaMilne, Roger LMarie Mulligan, AnnaMuranen, Taru ANevanlinna, HeliNeven, PatrickNielsen, Sune FNordestgaard, Børge GOlson, Janet EPerez, Jose IAPeterlongo, PaoloPhillips, Kelly-AnnePoole, Christopher JPylkäs, KatriRadice, PaoloRahman, NazneenRüdiger, ThomasRudolph, AnjaSawyer, Elinor JSchumacher, FredrickSeibold, PetraSeynaeve, CarolineShah, MitulSmeets, AnnSouthey, Melissa CTollenaar, Rob A E MTomlinson, IanTsimiklis, HelenUlmer, Hans-UlrichVachon, Celinevan den Ouweland, Ans MWVan’t Veer, Laura JWildiers, HansWillett, WalterWinqvist, RobertZamora, M PilarChenevix-Trench, GeorgiaDörk, ThiloEaston, Douglas FGarcía-Closas, MontserratKraft, PhillipHopper, John LZheng, WeiSchmidt, Marjanka KPharoah, Paul DP2018-04-192017Guo, Q., S. Burgess, C. Turman, M. K. Bolla, Q. Wang, M. Lush, J. Abraham, et al. 2017. “Body mass index and breast cancer survival: a Mendelian randomization analysis.” International Journal of Epidemiology 46 (6): 1814-1822. doi:10.1093/ije/dyx131. http://dx.doi.org/10.1093/ije/dyx131.http://nrs.harvard.edu/urn-3:HUL.InstRepos:35982170Abstract 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.en-USBody mass indexbreast cancer survivalMendelian randomizationepidemiologygeneticsJournal Article2018-04-1910.1093/ije/dyx131