Interstate differences in incidence and mortality from melanoma. A re-examination of the latitudinal gradient

To investigate the patterns of cutaneous malignant melanoma (CMM) mortality in Australia.

A descriptive analysis of melanoma incidence and mortality in Australia supplemented by a case series analysis of melanoma survival. Melanoma mortality rates were based on tabulations supplied by the Australian Bureau of Statistics for the years 1969-1989. Melanoma incidence rates were based on State cancer registry records for the years 1977-1990. The case series survival analysis was based on detailed individual records from the population-based cancer registries in Tasmania and South Australia.

The level of and rise in melanoma mortality rates during 1969-1989 in Australia; the five-year survival rates for Tasmanian and South Australian cases; and male:female incidence ratios related to latitude.

We found annual increases in melanoma mortality rates of 2.5% in men (P < 0.0001) and 1.1% in women (P < 0.0001) for all Australia. The five-year survival rates (with 95% confidence intervals [CI]) were: 67% (59%-75%) for Tasmanian men; 79% (76%-83%) for South Australian men; 80% (74%-86%) for Tasmanian women and 88% (86%-91%) for South Australian women. A change in the male:female incidence ratio with latitude was also found--women have significantly higher incidence rates at higher latitudes, but similar rates to men at lower latitudes.

The age standardised mortality from CMM for the period 1969 to 1989 shows little variation by State for women, despite a considerable range in latitude. CMM mortality in men is increasing at a faster rate than that in women. Between 1982 and 1987 the male:female incidence ratio in high latitudes in the Southern Hemisphere showed an excess of cases in women, a finding which we believe has not been reported before.