An analysis reported from the Nurses’ Health Study (NHS) shows that weight gain in premenopause years is an independent risk factor for postmenopausal breast cancer.1 This adds to the already well-documented studies showing that weight gain after menopause positively correlates with postmenopausal breast cancer.2,3

“There have been very few studies that have looked at premenopausal weight gain and breast cancer. Our study adds new insights on weight gain during premenopausal years and risk for postmenopausal breast cancer,” corresponding author Bernard Rosner, PhD, from the Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts told Cancer Therapy Advisor.

The NHS cohort was established in 1976; 121,701 female US registered nurses (aged 30 to 55 years) responded to a mail questionnaire on risk factors for breast cancer (reproductive factors, hormone therapy, anthropometric variable, benign breast disease, and family history of breast cancer). Responses were updated every 2 years up to the time of data analysis. Weight at age 18 was collected in 1980.

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Information on breast cancer diagnosis was also obtained. Estrogen receptor (ER) and progesterone receptor (PR) status of breast cancer was obtained from pathology reports. All cases of invasive breast cancer were included in this analysis.

Overall, 4965 cases of invasive breast cancer were reported for 74,177 women followed from 1980 to 2012. Of these, 2412 were ER+/PR+, 662 were ER-/PR-, and 598 were ER+/PR-.

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The investigators used a log-incidence model of breast cancer, which included 10 established non-modifiable risk factors; components of weight and weight change were added to this model.4-6