Background: Familial risks in kidney cancer and association with second primary malignancies were studied using the nationwide Swedish Family Cancer Database.
Methods: Cancer data were retrieved from the Swedish Cancer Registry from years 1961 to 1998 and included 23,137 cases of kidney cancer. Standardized incidence ratios (SIRs) were used to measure the cancer risks.
Results: Seventy-one families were identified where both a parent and an offspring had kidney cancer, giving a familial risk for offspring of 1.56 (1.22 to 1.95) and population attributable proportion of 0.78%. A risk for kidney cancer from an affected sibling was considerably higher with a SIR of 4.72 (2.28 to 9.20), giving an attributable proportion of 0.77%. The discordant tumor site that was associated with kidney cancer between two generations was hemangioblastoma of central nervous system. Discordant cancer sites that were associated with kidney cancer in siblings were ovaries, endocrine glands and pancreas. There was an over threefold increase of second primary malignancies of the urinary bladder, nervous system and endocrine gland in kidney cancer patients. The risks for second primary hemangioblastoma following kidney cancer or familial kidney cancer was 21.19 (6.69 to 43.83) and 1206 (114 to 3456), respectively.
Conclusions: The high ratio of sibling risk to offspring risk in kidney cancer may reflect a recessive susceptibility. The high risk for second primary cancers in the patients without family history is consistent with a polygenic model and variable degree of environmental modification.