Background: Family history is a strong risk factor for prostate cancer. The aim of this study was to investigate whether increased diagnostic activity is related to the incidence of prostate cancer among brothers of men with prostate cancer.
Methods: Data were from the nationwide population-based Prostate Cancer Database Sweden (PCBaSe Sweden), which includes data from the National Prostate Cancer Register, the Swedish Cancer Register, the Register of the Total Population, the Multi-Generation Register, and the Census database. We investigated the relationship of tumor characteristics, time from diagnosis of the index patient (i.e., prostate cancer patients in the National Prostate Cancer Register for whom at least one brother and their father could be identified), calendar period, geographic factors, and socioeconomic status to standardized incidence ratios (SIRs) for prostate cancer among 22 511 brothers of 13 975 index patients in PCBaSe Sweden.
Results: Brothers of index patients with prostate cancer were at increased risk for a diagnosis of prostate cancer (SIR = 3.1, 95% confidence interval [CI] = 2.9 to 3.3). Risk was higher for T1c tumors (SIR = 3.4, 95% CI = 3.2 to 3.8) than for metastatic tumors (SIR = 2.0, 95% CI = 1.5 to 2.6), and risk of T1c tumors was especially high during the first year after the diagnosis of the index patient (SIR = 4.3, 95% CI = 3.8 to 4.9), compared with the following years (SIR range = 2.8-3.3), and for brothers of index patients who had a higher socioeconomic status (SIR = 4.2, 95% CI = 3.7 to 4.7), compared with brothers of index patients with lower socioeconomic status (SIR = 2.8, 95% CI = 2.4 to 3.2).
Conclusions: Increased diagnostic activity among men with a family history of prostate cancer appears to contribute to their increased risk of prostate cancer and to lead to detection bias in epidemiological and genetic studies of familial prostate cancer.