Familial risks by proband status and age are useful for clinical counseling, and they can be used to calculate population-attributable fractions (PAFs), which show the proportion of disease that could be prevented if the cause could be removed.
The authors used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and 182,104 fathers and 3710 sons with medically verified prostate carcinoma to calculate age specific familial standardized incidence ratios (SIRs) with 95% confidence intervals (95%CI) and familial PAFs for prostate carcinoma in sons ages 0–66 years.
The incidence of prostate carcinoma was doubled between the years 1961 and 1998. The familial SIRs for prostate carcinoma were 2.38 (95%CI, 2.18–2.59) for men with prostate carcinoma in the father only, 3.75 (95%CI, 2.73–4.95) for men with prostate carcinoma in a brother only, and 9.44 (95%CI, 5.76–14.03) for men with prostate carcinoma in both a father and a brother. The corresponding familial PAFs were 8.86%, 1.78%, and 0.99%, respectively, yielding a total PAF of 11.63%. Age specific risks were shown for the same proband histories. The SIR was 8.05 for prostate carcinoma before age 55 if a brother had been diagnosed before that age. If, in addition, a father was diagnosed at any age, then the SIR was 33.09.
The authors recommend that having a brother who is diagnosed with prostate carcinoma before age 55 years or having a brother and father who are diagnosed at any age are indications to screen for prostate carcinoma. The familial PAF of prostate carcinoma among a population of sons ages 0–66 years was 11.63%. Cancer 2002;95:1346–53. © 2002 American Cancer Society.