A renowned cancer expert says we need a different approach to finding treatments for rare cancers.

Professor Ian Olver has written an editorial for the Medical Journal of Australia that says rare cancers account for 30 per cent of cancer deaths, yet less than 20 per cent of cancer research funding in Australia goes towards these cancers.

Professor Olver, director of the University of South Australia’s Sansom Institute for Health Research, said an audit published by Cancer Australia in 2014 showed more than 80 per cent of cancer research funding went to blood cancers and five solid cancers (breast, colorectal, prostate, melanoma and lung cancers).

Meanwhile, rare cancers such as pancreatic, ovarian and brain cancer received a much smaller slice of the funding pie.

Rare cancers are defined as those with an incidence of less than six cases per 100,000 people per year.

“If less research is being performed to provide data, and the low incidence of rare cancers makes large randomised clinical trials impractical, there are few evidence-based guidelines regarding rarer cancers to which clinicians can refer,” Prof Olver says.

The expert poses the question: If we are to prioritise research to improve the outcomes in less common cancers, what needs to be done?

He suggests ovarian cancer is a good example of how approaches to rare cancer treatment need to evolve.

“One feature of common cancers like breast cancer or bowel cancer, where survival has been significantly improved over recent years, is that there is a screening test for early detection,” he said.

“The heterogeneity of ovarian cancer suggests that a population screening test based on a panel of biomarkers will be difficult to achieve.”

However, he noted there are similarities between ovarian subtypes and other cancers, which he says will be helpful in identifying targets for new treatments. For example, high-grade serous carcinoma of the ovary shares similarities with triple-negative breast cancers.

Drugs used for metastatic breast cancer are now being trialled in patients with ovarian cancer.

“Our approach to clinical trials will need to be different in rare cancers where large randomised trials are impractical,” he says.

“Reassessing research into cancers or cancer subtypes classified as histologically rare may involve finding molecular and genetic similarities across a range of cancers which suggest that a targeted therapy in one may be successfully trialled in another.

“This requires national and international collaboration and linking datasets from biobanks and registries.”