title: Body size, physical activity, and risk of triple-negative and estrogen receptor-positive breast cancer.
abstract: BACKGROUND
  Triple-negative breast cancer, characterized by a lack of hormone receptor and HER2 expression, is associated with a particularly poor prognosis. Focusing on potentially modifiable breast cancer risk factors, we examined the relationship between body size, physical activity, and triple-negative disease risk.
  
  
  METHODS
  Using data from 155,723 women enrolled in the Women's Health Initiative (median follow-up, 7.9 years), we assessed associations between baseline body mass index (BMI), BMI in earlier adulthood, waist and hip circumference, waist-hip ratio, recreational physical activity, and risk of triple-negative (n=307) and estrogen receptor-positive (ER+, n=2,610) breast cancers.
  
  
  RESULTS
  Women in the highest versus lowest BMI quartile had 1.35-fold (95% CI, 0.92-1.99) and 1.39-fold (95% CI, 1.22-1.58) increased risks of triple-negative and ER+ breast cancers, respectively. Waist and hip circumferences were positively associated with risk of ER+ breast cancer (Ptrend=0.01 for both measures) but were not associated with triple-negative breast cancer. Compared with women who reported no recreational physical activity, women in the highest activity tertile had similarly lower risks of triple-negative and ER+ breast cancers (HR=0.77; 95% CI, 0.51-1.13; and HR=0.85; 95% CI, 0.74-0.98, respectively).
  
  
  CONCLUSIONS
  Despite biological and clinical differences, triple-negative and ER+ breast cancers are similarly associated with BMI and recreational physical activity in postmenopausal women. The biological mechanisms underlying these similarities are uncertain and these modest associations require further investigation.
  
  
  CONCLUSIONS
  If confirmed, these results suggest potential ways postmenopausal women might modify their risk of both ER+ and triple-negative breast cancers.
authors.affiliation: Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., M4-B402, P.O. Box 19024, Seattle, WA 98109-1024, USA. aphipps@fhcrc.org
authors.forename: Amanda I
authors.initials: AI
authors.lastname: Phipps
authors.forename: Rowan T
authors.initials: RT
authors.lastname: Chlebowski
authors.forename: Ross
authors.initials: R
authors.lastname: Prentice
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
authors.forename: Marcia L
authors.initials: ML
authors.lastname: Stefanick
authors.forename: Jean
authors.initials: J
authors.lastname: Wactawski-Wende
authors.forename: Lewis H
authors.initials: LH
authors.lastname: Kuller
authors.forename: Lucile L
authors.initials: LL
authors.lastname: Adams-Campbell
authors.forename: Dorothy
authors.initials: D
authors.lastname: Lane
authors.forename: Mara
authors.initials: M
authors.lastname: Vitolins
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Kabat
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rohan
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Li
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D049628:Body Size; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D016032:Randomized Controlled Trials as Topic; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D049629:Waist-Hip Ratio
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone