AUSTRALIAN scientists hope to find a way of blocking the re-growth of an aggressive type of lung cancer.

In a study released today, researchers say the discovery of a mechanism that causes the regrowth of small-cell lung cancer after chemotherapy offers hope for the creation of new therapies.

Monash Institute of Medical Research Professor Neil Watkins, who led the study, said many cancer treatments and trials focused on shrinking existing tumours using chemotherapy but this research focused on the potential for blocking a signal pathway to stop regrowth.

That signal pathway is known as Hedgehog.

"This discovery gives us important clues for designing new treatment approaches," Prof Watkins said.

"By using drugs to inhibit the Hedgehog signalling, we should be able to increase the effectiveness of chemotherapy and reduce the risk of cancer relapse."

In healthy cells, those signals control organ development and repair.

Lung cancer is the most common cause of cancer-related death in Australia, and the small-cell form makes up between 15 and 20 per cent of all cases.

Prof Watkins said the study, conducted by an international team of researchers across three universities and published in the journal Nature Medicine, would change the focus of cancer trials away from cancer shrinkage.

In another study released today, Queensland researchers reveal they have discovered two genetic variants that increase the risk of melanoma.

Lead researcher Dr Stuart MacGregor said the discovery of the variants would increase the ability to predict who is most at risk of developing the potentially deadly disease.

"This in turn means people will be better informed and can take the right precautions to avoid developing this increasingly common cancer," he said.

Unlike other risk variants found so far, Dr MacGregor said these new variants did not act by changing skin pigmentation or mole count.

"One variant appears to play a role in how DNA is repaired following damage by UV radiation, while the other variant may play a role in tumour formation," he said.

Melanoma is the least-common skin cancer type but the most dangerous.