Menopausal hormone therapy and subsequent risk of specific invasive breast cancer subtypes in the California Teachers Study.
BACKGROUND
Although it is well established that combined estrogen-progestin therapy (EPT) increases breast cancer risk, questions remain regarding the effect of different formulations of hormones, whether certain women are at particularly high risk, and whether risk varies by tumor subtype.


METHODS
We investigated hormone therapy (HT) use in relation to breast cancer risk in the California Teachers Study cohort; after a mean follow-up of 9.8 years, 2,857 invasive breast cancers were diagnosed.


RESULTS
Compared with women who had never used HT, women who reported 15 or more years of estrogen therapy (ET) use had a 19% greater risk of breast cancer (95% confidence interval, 1.03-1.37), whereas women using EPT for 15 or more years had an 83% greater risk (95% confidence interval, 1.48-2.26). Breast cancer risk was highest among women using continuous combined EPT regimens. Risks associated with EPT and ET use were increased with duration of HT use for women with a body mass index (BMI) of <29.9 kg/m(2) but not for women with BMI of >or=30 kg/m(2). Elevated risks associated with EPT and ET use were confined to tumors that were positive for both estrogen and progesterone receptors and those that were HER2+ but were slightly diminished for HER2- tumors.


CONCLUSIONS
Breast cancer risks increased with longer duration of ET and EPT use, and risks were highest for continuous-combined EPT use. Furthermore, risks varied by BMI and tumor subtype.


CONCLUSIONS
These findings underscore the need for personalized risk-benefit discussions with women contemplating HT use.
Saxena
Tanmai
T
Department of Preventive Medicine, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California, USA.
Lee
Eunjung
E
Henderson
Katherine D
KD
Clarke
Christina A
CA
West
Dee
D
Marshall
Sarah F
SF
Deapen
Dennis
D
Bernstein
Leslie
L
Ursin
Giske
G
D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology* / Q000473:pathology; D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D012307:Risk Factors