title: Body mass index, weight change, and risk of second primary breast cancer in the WECARE study: influence of estrogen receptor status of the first breast cancer.
abstract: Studies examining the relationship between body mass index (BMI) and risk of contralateral breast cancer (CBC) have reported mixed findings. We previously showed that obese postmenopausal women with estrogen receptor (ER)-negative breast cancer have a fivefold higher risk of CBC compared with normal weight women. In the current analysis, we reexamined this relationship in the expanded Women's Environmental Cancer and Radiation Epidemiology (WECARE) Study, focusing on the impact of menopausal status and ER status of the first breast cancer. The WECARE Study is a population-based case-control study of young women with CBC (cases, N = 1386) and with unilateral breast cancer (controls, N = 2045). Rate ratios (RR) and 95% confidence intervals (CI) were calculated to assess the relationship between BMI and risk of CBC stratified by menopausal and ER status. Positive associations with obesity and weight gain were limited to women who became postmenopausal following their first primary breast cancer. Among those with an ER-negative first breast cancer, obesity (vs. normal weight) at first diagnosis was associated with an increased risk of CBC (RR = 1.9, 95% CI: 1.02, 3.4). Also, weight gain of ≥10 kg after first diagnosis was associated with an almost twofold increased risk of CBC (RR = 1.9, 95% CI: 0.99, 3.8). These results suggest that women with an ER-negative first primary cancer who are obese at first primary diagnosis or who experience a large weight gain afterward may benefit from heightened surveillance. Future studies are needed to address the impact of weight loss interventions on risk of CBC.
authors.affiliation: University of Toronto, Dalla Lana School of Public Health Sciences, Toronto, Canada.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Brooks
authors.affiliation: Cancer Prevention Institute of California, Fremont, California.|Department of Health Research and Policy (Epidemiology), Stanford University School of Medicine, Stanford, California.
authors.forename: Esther M
authors.initials: EM
authors.lastname: John
authors.affiliation: Danish Cancer Society Research Center, Copenhagen, Denmark.
authors.forename: Lene
authors.initials: L
authors.lastname: Mellemkjaer
authors.affiliation: University of Iowa, Iowa City, Iowa.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Lynch
authors.affiliation: University of Toronto, Dalla Lana School of Public Health Sciences, Toronto, Canada.|Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Knight
authors.affiliation: Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Malone
authors.affiliation: Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Reiner
authors.affiliation: Beckman Research Institute, City of Hope National Medical Center, Duarte, California.
authors.forename: Leslie
authors.initials: L
authors.lastname: Bernstein
authors.affiliation: Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Liang
authors.affiliation: Department of Population Health, New York University School of Medicine, New York, New York.
authors.forename: Roy E
authors.initials: RE
authors.lastname: Shore
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Stovall
authors.affiliation: Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Jonine L
authors.initials: JL
authors.lastname: Bernstein
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001835:Body Weight; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D016609:Neoplasms, Second Primary / Q000453:epidemiology* / Q000209:etiology*; D011159:Population Surveillance; D011960:Receptors, Estrogen / Q000378:metabolism; D012306:Risk; D018426:SEER Program; D055815:Young Adult
chemical_list: D011960:Receptors, Estrogen
keywords: Body mass index; contralateral breast cancer; estrogen receptor