TY - JOUR
T1 - Reproductive factors and risk of premenopausal breast cancer by age at diagnosis
T2 - Are there differences before and after age 40?
AU - Warner, Erica T.
AU - Colditz, Graham A.
AU - Palmer, Julie R.
AU - Partridge, Ann H.
AU - Rosner, Bernard A.
AU - Tamimi, Rulla M.
N1 - Funding Information:
Acknowledgments Financial supports were received under Grants P01CA87969, and UM1CA176726 from the National Cancer Institute, the National Institutes of Health, Department of Health and Human Services. Dr. Colditz was supported in part by an American Cancer Society Cissy Hornung Clinical Research Professorship. Dr. Warner was supported by the National Institute of General Medical Sciences Grant 2R25GM055353-13 and the National Cancer Institute Grant 5T32CA009001-36. The authors would like to thank the participants and the staff of Nurses’ Health Study and Nurses’ Health Study II for their valuable contributions as well as the following state cancer registries for their help: AL, AZ, AR, CA, CO, CT, DE, FL, GA, ID, IL, IN, IA, KY, LA, ME, MD, MA, MI, NE, NH, NJ, NY, NC, ND, OH, OK, OR, PA, RI, SC, TN, TX, VA, WA, and WY. In addition, this study was approved by the Connecticut Department of Public Health (DPH) Human Investigations Committee. Certain data
PY - 2013/11
Y1 - 2013/11
N2 - We examined the relationship between reproductive factors and risk of premenopausal breast cancer among women less than age 40 compared with older premenopausal women. We documented 374 incident cases of breast cancer diagnosed before age 40, and 2,533 cases diagnosed at age 40 and older among premenopausal women in the Nurses' Health Study cohorts. Biennial questionnaires were used to determine age at menarche, age at first birth, parity, breastfeeding, and other reproductive factors. Multivariate relative risks (RR) and 95 % confidence intervals (CI) were calculated using Cox proportional hazards models within age at diagnosis groups. Tumors in younger women were significantly more likely to be higher grade, larger size, and hormone receptor negative than were tumors in older premenopausal women (p < 0.0001). There was no significant heterogeneity according to age in associations between reproductive factors and risk of premenopausal breast cancer. First birth at age 30 or older increased breast cancer risk in both age groups (age <40: RR 1.10, 95 % CI 0.80-1.50; age ≥40: RR 1.16, 95 % CI 1.02-1.32; p-heterogeneity = 0.44). Risk of premenopausal breast cancer decreased with each additional year of age at menarche in both age groups (age <40: RR 0.93, 95 % CI 0.87-0.99; p trend = 0.02; age ≥40: RR 0.94, 95 % CI 0.91-0.97; p trend = <0.0001). Among premenopausal parous women, breastfeeding was protective regardless of age at diagnosis (age <40: RR 0.84, 95 % CI 0.57-1.22; age ≥40: RR 0.85, 95 % CI 0.72-0.99; p-heterogeneity = 0.79). In the largest prospective examination of reproductive risk factors and risk of breast cancer before and after age 40, we found that younger women were more likely to develop tumors with less favorable prognostic characteristics. However, associations between reproductive factors and risk of breast cancer were similar regardless of age at diagnosis of premenopausal breast cancer.
AB - We examined the relationship between reproductive factors and risk of premenopausal breast cancer among women less than age 40 compared with older premenopausal women. We documented 374 incident cases of breast cancer diagnosed before age 40, and 2,533 cases diagnosed at age 40 and older among premenopausal women in the Nurses' Health Study cohorts. Biennial questionnaires were used to determine age at menarche, age at first birth, parity, breastfeeding, and other reproductive factors. Multivariate relative risks (RR) and 95 % confidence intervals (CI) were calculated using Cox proportional hazards models within age at diagnosis groups. Tumors in younger women were significantly more likely to be higher grade, larger size, and hormone receptor negative than were tumors in older premenopausal women (p < 0.0001). There was no significant heterogeneity according to age in associations between reproductive factors and risk of premenopausal breast cancer. First birth at age 30 or older increased breast cancer risk in both age groups (age <40: RR 1.10, 95 % CI 0.80-1.50; age ≥40: RR 1.16, 95 % CI 1.02-1.32; p-heterogeneity = 0.44). Risk of premenopausal breast cancer decreased with each additional year of age at menarche in both age groups (age <40: RR 0.93, 95 % CI 0.87-0.99; p trend = 0.02; age ≥40: RR 0.94, 95 % CI 0.91-0.97; p trend = <0.0001). Among premenopausal parous women, breastfeeding was protective regardless of age at diagnosis (age <40: RR 0.84, 95 % CI 0.57-1.22; age ≥40: RR 0.85, 95 % CI 0.72-0.99; p-heterogeneity = 0.79). In the largest prospective examination of reproductive risk factors and risk of breast cancer before and after age 40, we found that younger women were more likely to develop tumors with less favorable prognostic characteristics. However, associations between reproductive factors and risk of breast cancer were similar regardless of age at diagnosis of premenopausal breast cancer.
KW - Age at diagnosis
KW - Breast cancer
KW - Reproductive factors
KW - Young women
UR - http://www.scopus.com/inward/record.url?scp=84888270339&partnerID=8YFLogxK
U2 - 10.1007/s10549-013-2721-9
DO - 10.1007/s10549-013-2721-9
M3 - Article
C2 - 24136668
AN - SCOPUS:84888270339
SN - 0167-6806
VL - 142
SP - 165
EP - 175
JO - Breast Cancer Research and Treatment
JF - Breast Cancer Research and Treatment
IS - 1
ER -