Background: Nulliparity is an endometrial cancer risk factor, but whether or not this association is due to infertility is unclear. Although there are many underlying infertility causes, few studies have assessed risk relations by specific causes.Methods:We conducted a pooled analysis of 8153 cases and 11 713 controls from 2 cohort and 12 case-control studies. All studies provided self-reported infertility and its causes, except for one study that relied on data from national registries. Logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).Results:Nulliparous women had an elevated endometrial cancer risk compared with parous women, even after adjusting for infertility (OR=1.76; 95% CI: 1.59-1.94). Women who reported infertility had an increased risk compared with those without infertility concerns, even after adjusting for nulliparity (OR=1.22; 95% CI: 1.13-1.33). Among women who reported infertility, none of the individual infertility causes were substantially related to endometrial cancer.Conclusions:Based on mainly self-reported infertility data that used study-specific definitions of infertility, nulliparity and infertility appeared to independently contribute to endometrial cancer risk. Understanding residual endometrial cancer risk related to infertility, its causes and its treatments may benefit from large studies involving detailed data on various infertility parameters.
Bibliographical noteFunding Information:
We thank many individuals who participated and the numerous institutions and their staff who supported the individual studies. We also thank Dr Leah Mechanic at NCI’s Division of Cancer Control and Population Sciences for her support in the E2C2 activities. Individual studies were funded by the following grants and agencies: ALBERTA (Cancer Institute of Canada with funds from the Canadian Cancer Society and the Canadian Institute for Health Research, NIH R01 CA082838, CMF is supported by career awards from Alberta Innovates-Health Solutions and the Alberta Cancer Foundation through the Weekend to End Women’s Cancers Breast Cancer Chair, LSC was supported through the Canada Research Chairs program); ANECS (National Health and Medical Research Council (NHMRC, grant #339435) of Australia and the Cancer Councils of Queensland and Tasmania; PMW and ABS are supported by Fellowships from the NHMRC); CECS (NIH R01 CA098346); EDGE (NIH R01 CA83918; P30CA008748); HAW (NIH P01 CA33619, R01 CA58598, N01 CN67001, N01 PC35137); IWHS (NIH R01 CA39742); NYU (NIH/NCI grants R01 CA098661 and R01 CA08121, and Center grant P30 CA016087); PECS (Intramural Research Funds of the NCI, NIH, Department of Health and Human Services); PEDS; SECS (NIH Grant No. R01 CA092585); TURIN (Italian Association for Research on Cancer and Ricerca Finalizzata Regione Piemonte); US (Intramural Research Funds of the NCI, NIH, the Department of Health and Human Services); USC (NIH R01 CA48774 and P30 CA14089); WLHS (the Swedish Research Council, Swedish Cancer Society and the Hans-Olov Distinguished Professor Award at Karolinska Institutet (Dnr:2368-10-221).
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