Association of time since last birth, age at first birth and parity with breast cancer survival among parous women; a register- based study from Norway
International Journal of Cancer, 05/07/2012
Alsaker MDK et al. – Reproductive factors were associated with survival from breast cancer diagnosed before, but not after age 50 years. Young women had a particularly poor prognosis throughout the study period.Methods
- We combined information from two population based registries and obtained information on 16 970 parous women with invasive breast cancer.
- Cox regression analysis was used to assess breast cancer survival in relation to age at diagnosis, age at first birth, time since last birth and parity.
- We stratified the analyses by age at diagnosis (<50 and >/= 50 years) as an approximation for menopausal age.
- In women diagnosed before 50 years of age, breast cancer survival was reduced with younger age at diagnosis (p for trend <0.001), whereas in women diagnosed at 50 years or later, survival was reduced with older age at diagnosis (p for trend 0.011).
- For breast cancer diagnosed before 50 years, survival was poorer in women with four or more births compared to women with one or two births (HR 1.3, 95 % CI 1.1-1.6).
- A short time since last birth was associated with reduced survival (p for trend 0.05), but adjustment for stage and grade attenuated the association.
- Among women diagnosed at 50 years or later, we found no association with survival for any of the reproductive factors.