The cancer prediction we’ve been getting wrong


THE risk of being diagnosed with and dying of cancer has been overestimated, prompting calls to overhaul the estimation methods, according to new research published today.

The Australian Institue of Health and Welfare (AIHW) estimates the lifetime risks of cancer diagnosis and mortality but its method assumes there are no competing causes of death, which could over-estimate the risks according to new research in the Medical Journal of Australia.

Research led by West Moreton Hospital and Health Service's Dr Anthea Bach and Westmead Hospital's Dr Kelvin Lo analysed AIHW data on age-specific cancer incidence and mortality for breast, colorectal, prostate, melanoma and lung cancers and mortality between 1982 -2013.

Researchers calculated the lifetime risks of cancer diagnosis and cancer-specific deaths and competing mortality, comparing estimates with risks published by the AIHW.

"AIHW estimates were consistently higher than our competing mortality-adjusted estimates of lifetime risks of diagnosis and death for all five cancers," authors said.

"Differences between AIHW and adjusted estimates declined with time for breast, prostate, colorectal, and men's lung cancers but remained steady for women's lung cancer and melanoma of the skin."

The research showed that the AIHW's lifetime risk of diagnosis compared with the adjusted risk respectively was 12.7% and 12.1% for breast cancer, 18.7% and 16.2% for prostate cancer, and 9% and 7% for men and 6.4% and 5.5% for women for colorectal cancer.

And the risk for skin melanoma was 7.5% and 6.0% for men and 4.4% and 4.0% for women, and for lung cancer 7.6 per cent compared with 5.8 % for men and 4.5 per cent and 3.9% for women.

"Our results indicate that cancer agencies, including the AIHW, may over-estimate the risks of people being diagnosed with or dying from a particular cancer."

"As lifetime risk estimates are widely cited in health promotion campaigns, they may cause public misperceptions of the risk of a cancer diagnosis or death,'' the authors wrote.

"Australian agencies should consider adopting methods for adjusting for competing mortality when estimating lifetime risks, as currently employed in North America and the United Kingdom, to increase the accuracy of their estimates."

AIHW's Head of Health Group, Mr Richard Juckes said while the competing mortality method used by the research had advantages, the AIHW's method was best suited for international comparisons and backed by the World Health Organisation and the International Association of Cancer Registries.

"For the purpose of international comparisons it is better to have Australian estimates calculated on the same basis as other countries than to use estimates that aren't as comparable," he said.

"The AIHW regularly consults with its Cancer Monitoring Advisory Group which provides expert advice to the institute in relation to cancer monitoring and reporting."

"This group hasn't recommended a change to the methodology used by the AIHW to calculate cancer risk, however, the AIHW plans to seek their advice in relation to this issue."