Practically all data on familial risk in ovarian and other cancers are based on incident cancer, whereas familiality in cancer mortality is largely unknown. If fatal forms of cancer are a highly familial subtype, then familial risk for mortality may exceed that of incidence, which is relevant for clinical decision making and counseling.
Ovarian cancer patients in the nationwide Swedish Family Cancer Database were classified according to fatal and nonfatal (incident) family history. Familial risks for incident and fatal ovarian cancer were calculated for offspring based on their parental or sibling family history of any cancer using standardized incidence ratios (SIRs) for incidence and standardized mortality ratios (SMRs) for mortality. Offspring without family history were referents.
The database included 24,757 mothers and 8138 daughters with ovarian cancer. When a mother had ovarian cancer, the SIR for incident ovarian cancer in daughters was 2.69, and when a sister had ovarian cancer it was 3.49. The SMRs for fatal cancer by fatal cancer in probands were 3.39 and 5.80, respectively. For fatal serous cancers among siblings, the SMR was 6.16, compared with 10.01 for the endometrioid type. Ovarian cancer was associated with maternal (SIR, 1.22; SMR, 1.56) and sororal breast cancer (SIR, 1.27). Another discordant association was between ovarian and paternal prostate cancer (SIR, 1.12; SMR, 1.66).
Fatal familial risks were higher for concordant ovarian, ovarian-breast, and ovarian-prostate cancers than the corresponding incident risks. This may suggest that highly fatal subtypes exist for these cancers, calling for genetic dissection. Cancer 2011. © 2011 American Cancer Society.