Incidence of Urogenital Cancers in Gunma Prefecture, Japan: A 10‐Year Summary

Background: Although the incidence of urogenital cancers in Japan is lower than that of other cancers, it is increasing steadily. Thus, an epidemiologic study was necessary to determine the measures that would decrease the mortality rate associated with these cancers. Methods: The subjects were 4759 patients with urogenital cancer who were living in Gunma Prefecture and who were newly diagnosed between 1985 and 1994. The data were analyzed by year and by patients' ages. The incidence rates of each disease were expressed as the number of cases per 100,000/year, and age-adjusted rates were adjusted to the world population. Results: The number of males and females afflicted by urogenital cancers increased over the 10-year period. The increase in age-adjusted incidence rates was sharpest for prostate, renal cell, and testicular cancers among males, and for renal cell, renal pelvic and ureter cancers among females. When age-specific rates were plotted against age on double logarithmic scales, the cancers were classified as type 1 (linear), type 2 (linear until a certain age, then flattening out or decreasing), or type 3 (irregular) based on the slope of the line. The magnitude of increase in the age-specific incidence rates of type 1 cancers with age was on the order of the 12th power for prostate cancer and the 5th power for bladder cancer. When the 10 years were divided into 2 periods (earlier and later), the age-specific incidence rates of prostate and renal cell cancers increased in all age groups, whereas the age-specific incidence rates of cancers that increased less sharply remained stable or even declined in some age groups. Conclusion: These epidemiologic data should be useful in reducing the mortality rates associated with these cancers.