Familial risks for eye melanoma and retinoblastoma: results from the Swedish Family-Cancer Database

No systematic population-based studies have been conducted on familial eye cancers. Reliable data on familial risks are important for clinical counselling and cancer genetics. The current analysis was based on the nation-wide Swedish Family-Cancer Database on 10.5 million individuals, containing families with parents and offspring. Cancer data were retrieved from the Swedish Cancer Registry from the years 1958 to 2002, including 3636 patients with any type of eye cancer. Familial risk for offspring was defined using the standardized incidence ratio (SIR), adjusted for many variables. Ocular melanoma was detected in two parent–offspring pairs, but the SIR of 3.90 was not significant. Parental upper aerodigestive tract (2.05), left-sided colon (1.83) and male non-medullary thyroid (6.98) cancers showed an association with ocular melanoma, albeit some with a borderline significance. The SIR for leukaemia was increased when parents were diagnosed with eye melanoma. There was no evidence for the association of ocular melanoma with cutaneous melanoma. The SIR for ocular melanoma was 1.76 when a sister was diagnosed with breast cancer, but there was no increase when a mother was diagnosed with breast cancer. When both a child and the parent presented with retinoblastoma, the SIR was 900. The parents of children with retinoblastoma had an excess of small intestinal and rectal cancers and Hodgkin's disease. The present findings were based on a limited number of cases, but they display a complex and heterogeneous pattern of familial associations in ocular melanoma, including an association with breast cancer through a putative recessive mechanism.