"We're watching it very closely because if the trend continues, New Zealand could eventually shake off its reputation for having the world's highest rate of melanoma."
The optimism comes as another study points to an alarming number of Kiwis failing to slip, slop and slap.
Whiteman warned that was the only cause for possible optimism in New Zealand's otherwise grim melanoma statistics, and the need to keep up messages about the importance of sunscreen.
"People who were teenagers in the 1950s and 60s still have really high rates of melanoma and the number of New Zealanders dying from melanoma – mainly older people – is still really high.
"Death rates from melanoma are higher in New Zealand than in Australia and are still going up."
Whiteman said there's a suspicion that New Zealanders are presenting with melanomas later than Australians for some reason and that their melanomas are thicker.
There are also other differences, particularly the easier availability in Australia of the new generation of drugs, the immune checkpoint inhibitors, that trick the body's immune system into recognising and fighting cancer, he said.
"If these are as effective as people believe, rates of melanoma deaths in Australia should start to fall relatively rapidly.
"If there's no equivalent decline in New Zealand, a link can be made to the lack of availability of the drugs here."
Whiteman said while sunscreen was effective in reducing the risk of melanoma, there is much stronger regulation around sunscreens in Australia than in New Zealand, where they are classified as cosmetics and compliance with the standard is voluntary.
"In Australia, sunscreens come under the Therapeutic Goods Administration (TGA), which polices the regulations heavily and will take products off the shelves that haven't gone through the TGA approval process.
"Australians are sometimes a bit envious of New Zealand's light touch to some areas of regulation. But the downside in relation to sunscreens is that some products sold as 'sunscreens' fail to comply with the standard, so consumers aren't getting the protection they think they are.
"Regulating sunscreens doesn't make them more expensive, but it does protect consumers."