“The size [of the study], as well as the fact that it confirms what has been seen in multiple other studies, means that this association is unlikely to be attributable to bias,” Therese Bevers, MD, professor of clinical cancer prevention at MD Anderson Cancer Center in Houston, Texas, told Cancer Therapy Advisor. Dr Bevers was not involved in the research. “I see more strengths than concerns, even though it is an indirect study.”

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Hormone receptor status was known for 7812 of the participants who developed breast cancer. An analysis revealed that as BMI increased, the risk for estrogen receptor (ER)-positive and/or progesterone receptor (PR)-positive premenopausal breast cancers decreased across all age groups. A similar inverse association, though weaker, was observed for hormone-receptor negative breast cancer in the youngest age group (18-24 years), but no association was seen in the older groups.

“Certainly the fact that [high BMI] prevents or decreases the risk of ER-/PR-positive breast cancers, but not ER-/PR-negative, suggests there probably is a component of a hormonal mechanism, but what exactly is that?” questioned Dr Bevers. “That seems to fly in the face of what we commonly think.”

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“We need additional research to understand the biological pathways behind the inverse association we report between BMI and premenopausal breast cancer,” concluded Dr Nichols. “These pathways could include hormonal mechanisms, but could also be related to differences in breast tissue composition in women with higher BMI, or alterations to other growth factors.”


  1. Schoemaker MJ, Nichols HB, Wright LB, et al. Association of body mass index and age with subsequent breast cancer risk in premenopausal women [published online June 21, 2018]. JAMA Oncol. doi: 10.1001/jamaoncol.2018.1771