Birth rates among male cancer survivors and mortality rates among their offspring: a population-based study from Sweden

Background: With improvements in treatment of cancer, more men of fertile age are survivors of cancer. This study evaluates trends in birth rates among male cancer survivors and mortality rates of their offspring. Methods: From the Swedish Multi-generation Register and Cancer Register, we identified 84,752 men ≤70 years with a history of cancer, for which we calculated relative birth rates as compared to the background population(Standardized Birth Ratios, SBRs). We also identified 126,696 offspring of men who had cancer, and compared their risks of death to the background population(Standardized Mortality Ratio, SMRs). Independent factors associated with reduced birth rates and mortality rates were estimated with Poisson modelling. Results: Men with a history of cancer were 23 % less likely to father a child compared to the background population(SBR 0.77, 95 % Confidence Interval[CI] 0.75-0.79). Nulliparous men were significantly more likely to father a child after diagnosis (SBR 0.81, 95 % CI 0.79-0.83) compared to parous men (SBR 0.68, 95 % CI 0.66-0.74). Cancer site(prostate), onset of cancer during childhood or adolescence, parity status at diagnosis(parous), current age(>40 years) and a recent diagnosis were significant and independent predictors of a reduced probability of fathering a child after diagnosis. Of the 126,696 children born to men who have had a diagnosis of cancer, 2604(2.06 %) died during follow up. The overall mortality rate was similar to the background population(SMR of 1.00, 95 %CI 0.96-1.04) and was not affected by the timing of their birth in relation to father's cancer diagnosis. Conclusion: Male cancer survivors are less likely to father a child compared to the background population. This is influenced by cancer site, age of onset and parity status at diagnosis. However, their offspring are not at an increased risk of death.