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.