Association of parity and ovarian cancer risk by family history of breast or ovarian cancer in a population-based study of postmenopausal women.
Although parity is associated with a decreased risk of ovarian cancer in the general population, this association among women with a family history is less clear. We examined this question in a prospective cohort of 31,377 Iowa women 55-69 years of age at baseline. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated through Cox regression. We identified 181 incident epithelial ovarian cancers through 13 years of follow-up. At baseline, 14% of the women reported breast or ovarian cancer in a first-degree relative, and an additional 12% reported a family history in a second-degree relative. Among women without a family history of breast or ovarian cancer in a first-degree relative, nulliparous women were at slightly increased risk of ovarian cancer (RR = 1.4, 95% CI = 0.9-2.4) compared with parous women, whereas among women with a family history, nulliparous women were at a much higher risk (RR = 2.7, 95% CI = 1.1-6.6) than parous women. Similar results were seen when family history included first- or second-degree relatives with breast or ovarian cancer or a first- or second-degree relative with ovarian cancer only. Nulliparity may be more strongly associated with an increased risk of ovarian cancer among women with a family history of breast or ovarian cancer, compared with women who do not have a family history of those cancers.
Vachon
Celine M
CM
Department of Health Sciences Research, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA. vachon@mayo.edu
Mink
Pamela J
PJ
Janney
Carol A
CA
Sellers
Thomas A
TA
Cerhan
James R
JR
Hartmann
Lynn
L
Folsom
Aaron R
AR
D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D006801:Humans; D015994:Incidence; D007484:Iowa / Q000453:epidemiology; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D010298:Parity; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors