Prostate cancer in Rochester, Minnesota (USA), from 1935 to 1989: increases in incidence related to more complete ascertainment

Prostate cancer incidence among White men in the United States climbed steadily from 45 per 10⁵ person-years (PY) during 1945-54 to 102 per 10⁵ PYs in 1988. To determine whether this increase might be the result of changing diagnostic practices, we examined trends in incidence and method of diagnosis in Rochester, Minnesota (US), from 1935 to 1989. We found a parallel increase in Rochester in non-autopsy diagnoses from 44 (95 percent confidence interval [CI]=29-58) cases per 10⁵ PYs in 1935-44 to 71 (CI=52-89) cases per 10⁵ PYs in 1985-87 which was driven by diagnoses prompted by digital rectal examination. There was no evidence that an increasing proportion of cases was found as the result of procedures to treat the symptoms of benign prostatic hyperplasia. Including autopsy diagnoses, incidence was stable over this extended interval and was 77 per 10⁵ PYs (CI=58-97) in 1935-44 and 72 per 10⁵ PYs (CI=53-91) in 1985-87. Incidence more than doubled after introduction of diagnostic serum prostate-specific antigen (PSA) assay and was 179 per 10⁵ PYs (CI=145-214) in 1988-89. We conclude that prostate-cancer incidence rates are influenced strongly by diagnostic practices and that national increases could reflect, to a large extent, more complete and earlier ascertainment rather than more frequent disease.