The success of checkpoint inhibitors in reducing Australia’s death rates from melanoma may eventually lead to non-melanoma skin cancers causing more deaths, according to a Victorian dermatologist.
While mortality rates from melanoma have declined since 2011, the incidence of non-melanoma skin cancers continues to increase at a concerning rate, says Dr Douglas Czarnecki, of the Department of Dermatology, Doctors’ Care Centre, Melbourne.
Writing in the International Journal of Dermatology, he notes that age standardised mortality rates for melanoma rose steadily from 1981 to a peak in 2011 but have since been in decline.
Figures from the Australian Institute of Health and Welfare show that melanoma crude mortality rates doubled from 4.2/100,000 in 1981 to 8.7/100,000 in 2011 then fell to 7.0/100,000. The total number of melanoma deaths per year over the same period rose from 571 to 1545, then declined to 1281 in 2016. For non-melnoma skin cancers the absolute numbers rose from 192 in 1981 to 679 in 2016.
The decline in melanoma deaths is presumably due to the increasing availability of effective treatments for metastatic melanoma treatment such as immune checkpoint inhibitors, says Dr Czarnecki.
But with the Australian population expanding with a higher proportion of low risk people from Asia, the Middle East, the Pacific Islands, and Africa, there may be a continuing rise in incidence of melanoma in susceptible high risk people, he believes.
“[The decrease in mortality] is not due to early detection of melanoma since the number of invasive melanomas excised from Australians is increasing by an average of 11% a year and the incidence of thick melanomas (>4 mm) is also increasing,” he notes.
Other cancer epidemiologists have said the ‘population dilution’ effect overestimates the effect on melanoma incidence and they maintain that public health skin cancer prevention campaigns have been effective in reducing the incidence of melanoma in younger Australians.
However Dr Czarnecki also warns the mortality rate for non-melanoma skin cancers shows no sign of easing and is increasing by an average 8% a year, almost tripling between 1981 and 2016.
“If this trend continues, non-melanoma skin cancers will soon kill more Australians than melanoma. The rising rate of mortality is more evidence that public health campaigns that have been running in Australia since 1981 are not having their desired outcome,” he concludes.