BRCA1 and BRCA2 mutation carriers in the Breast Cancer Family Registry: an open resource for collaborative research

Prediagnosis reproductive factors and all-cause mortality for women with breast cancer in the breast cancer family registry

Studies have examined the prognostic relevance of reproductive factors before breast cancer diagnosis, but most have been small and their overall findings inconclusive. Associations between reproductive risk factors and all-cause mortality after breast cancer diagnosis were assessed with the use of a population-based cohort of 3,107 women of White European ancestry with invasive breast cancer (1,130 from Melbourne and Sydney, Australia; 1,441 from Ontario, Canada; and 536 from Northern California, United States). During follow-up with a median of 8.5 years, 567 deaths occurred. At recruitment, questionnaire data were collected on oral contraceptive use, number of full-term pregnancies, age at first full-term pregnancy, time from last full-term pregnancy to breast cancer diagnosis, breastfeeding, age at menarche, and menopause and menopausal status at breast cancer diagnosis. Hazard ratios for all-cause mortality were estimated with the use of Cox proportional hazards models with and without adjustment for age at diagnosis, study center, education, and body mass index. Compared with nulliparous women, those who had a child up to 2 years, or between 2 and 5 years, before their breast cancer diagnosis were more likely to die. The unadjusted hazard ratio estimates were 2.75 [95% confidence interval (95% CI), 1.98-3.83; P < 0.001] and 2.20 (95% CI, 1.65-2.94; P < 0.001), respectively, and the adjusted estimates were 2.25 (95% CI, 1.59-3.18; P < 0.001) and 1.82 (95% CI, 1.35-2.46; P < 0.001), respectively. When evaluating the prognosis of women recently diagnosed with breast cancer, the time since last full-term pregnancy should be routinely considered along with other established host and tumor prognostic factors, but consideration of other reproductive factors may not be warranted.

Family history of breast cancer and all-cause mortality after breast cancer diagnosis in the Breast Cancer Family Registry

Although having a family history of breast cancer is a well established breast cancer risk factor, it is not known whether it influences mortality after breast cancer diagnosis. We studied 4,153 women with first primary incident invasive breast cancer diagnosed between 1991 and 2000, and enrolled in the Breast Cancer Family Registry through population-based sampling in Northern California, USA; Ontario, Canada; and Melbourne and Sydney, Australia. Cases were oversampled for younger age at diagnosis and/or family history of breast cancer. Carriers of germline mutations in BRCA1 or BRCA2 were excluded. Cases and their relatives completed structured questionnaires assessing breast cancer risk factors and family history of cancer. Cases were followed for a median of 6.5 years, during which 725 deaths occurred. Cox proportional hazards regression was used to evaluate associations between family history of breast cancer at the time of diagnosis and risk of all-cause mortality after breast cancer diagnosis, adjusting for established prognostic factors. The hazard ratios for all-cause mortality were 0.98 (95% confidence interval [CI] = 0.84-1.15) for having at least one first- or second-degree relative with breast cancer, and 0.85 (95% CI = 0.70-1.02) for having at least one first-degree relative with breast cancer, compared with having no such family history. Estimates did not vary appreciably when stratified by case or tumor characteristics. In conclusion, family history of breast cancer is not associated with all-cause mortality after breast cancer diagnosis for women without a known germline mutation in BRCA1 or BRCA2. Therefore, clinical management should not depend on family history of breast cancer.