Familial aggregation of testicular cancer among early-onset cancer survivors. A prospective observational cohort data from Finland.

Testicular cancer (TC) is the most common form of cancer in men aged 15-35 years. Familial risk for TC is among highest of all cancers.
Material and Methods: A prospective observational cohort of 9111 relatives in 2,188 families of early-onset TC patients, called probands, diagnosed at age ≤40 years in Finland between 1970 and 2012. Standardized incidence ratios (SIR) were used as measures of familial aggregation for early-onset (≤40 years) TC. Follow-up ended at diagnosis of TC, death or 31 December 2014 whichever earliest.
Results: Among first-degree relatives of early-onset TCs, in all 12 early-onset TC cases (0.24%) were diagnosed over the follow-up; the SIR for any first-degree relative was 4.59 (95% confidence interval (CI): 2.37-8.01) and for brothers the SIR was 6.51 (95% CI 3.12-11.96).
Discussion: Familial aggregation of TC shows substantial risk for early-onset TC among first-degree relatives of early-onset TC patients in Finland. This is important to acknowledge to avoid diagnostic delay especially of TC.
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