Lower breast cancer survival in mothers of children with a malignancy: a national study.

As it is unclear if hereditary factors affect breast cancer survival, this was compared using fertility and cancer registry data, among all women so diagnosed during 1961-1999 in Sweden, having a child with childhood cancer (<or=20 years of age; n=254) and with that of other women (n=74,781). Those having a child with a childhood malignancy had a significantly worse survival than other women, relative risk (RR)=1.25, 95% CI 1.02-1.55, P<0.04, adjusted for age at diagnosis, year of diagnosis, parity and time since last pregnancy. Childhood sarcomas or acute myeloid leukaemia seemed to be most associated with a worse survival in the mother (RR=1.38 and 1.69, respectively). The lower survival of the mother was present for breast cancer diagnosed both before and after 50 years of age. The Li-Fraumeni syndrome and possibly other genetic disorders may lower breast cancer survival.