Trends by anatomic site in the incidence of cutaneous malignant melanoma in Canada, 1969-93.

Trends in melanoma incidence by anatomic site were examined in Canada where ascertainment of cancer has been of a high standard. The analysis included 41,239 malignant melanomas registered between 1969 and 1993 and used an age, period and cohort modeling approach. The estimated annual increase was 4.8% for males and 3.1% for females but slowed appreciably in the later years. The lifetime risk of melanoma appeared to have peaked with women born about 1934 and men born about 1944. The age-standardized rates have now stabilized for women and are expected to plateau for men in the near future. The largest relative increases occurred for the upper limbs followed by the trunk for both sexes. Comparable generation effects were observed for intermittently exposed sites but the patterns of trend differed between sites for men and women. This supports effects due to sex- and site-specific pattern of sun exposure. The evidence, for the first time, of more favorable trends among post-World War II generations is thought to reflect reduced exposure to UV rays. This may possibly be the earliest signs of the impact of primary prevention programs, particularly if UV radiation also acts as a tumor promoter.