The effect of female sex hormones on cancer survival. A register-based study in patients younger than 20 years at diagnosis.

The hypothesis that the female survival advantage in many cancers is dependent on sexual maturity was tested in a population-based cohort. Complete follow-up through 1986 was achieved in virtually all 6262 individuals in Sweden who were diagnosed from 1960 through 1984 as having a malignant disease before the age of 20 years. Proportional hazards analysis revealed a 22% lower death rate overall in females than in males. The difference was unrelated to age at diagnosis for tumors arising in the nervous system and the hematopoietic system (lymphomas and leukemias) but strongly dependent on age for sarcomas and, notably, for all remaining cancers--mostly epithelial. Males and females had similar hazard rates for epithelial cancers before the age of 11 years. At ages 11 to 19 years, the rates in females were 55% to 65% lower than in males. One conceivable explanation for these findings is that female sex hormones prevent the establishment of distant metastases in certain malignant diseases.