Risk of death for some melanomas less than 1%: Study

Research published in CANCER has found evidence that some cases of melanoma are much less likely to cause death, with one subset of patients – comprising a quarter of the study’s 11,592 participants – found to have a less than 1% risk of dying.
 
The study is the latest in a slew of new research investigating ‘non-harmful melanomas’ and has renewed concerns regarding overdiagnosis, but GP and skin cancer expert Adjunct Associate Professor Jeremy Hudson says the new findings should not prompt a change in clinical practice.
 
‘Overdiagnosis is a very poorly defined word in general,’ he said.
 
‘From an epidemiological point of view, it means treating something that would not have harmed the patient. A good example of overdiagnosis is small pulmonary emboli now picked up on high resolution CT, which will not kill patients.
 
‘The problem is when laypeople or poorly informed policymakers think overdiagnosis means doctors are deliberately overtreating.
 
‘Doctors still need to diagnose and excise all early melanomas. A certain number may not kill patients, but we lack the ability to tell which ones.’
 
The US study analysed 11,592 patients using a cancer registry and identified a subset of 25% of patients that had a risk of dying from melanoma below 1%. The overall seven-year mortality rate was 2.5%.
 
The analysed patients had stage one melanoma that was 1.0 mm or less in thickness and had not spread to the lymph nodes. Models were developed to identify patients with a very low risk of dying of melanoma.
 
Attributes of the lower risk group included younger age at diagnosis, Clark level II, Breslow thickness below 0.4 mm, absence of mitogenicity, absence of ulceration and female sex.
 
To differentiate the ‘low risk’ cases from other more dangerous melanomas, the researchers suggested the creation of a new classification called ‘melanocytic neoplasm of low malignant potential’.
 
However, Associate Professor Hudson, who is Clinical Director of the North Queensland Skin Centre and Chair of RACGP Specific Interests Dermatology, believes the wording is unnecessary.
 
‘I would prefer to be direct and just tell my patients they had a low-risk melanoma and give them precise numbers if they prefer it. Australians are quite cluey about melanomas,’ he said.
 
‘There have been several recent studies suggesting that some early melanomas may not kill people if left alone and finding these would technically be overdiagnosis … [but] the safest current approach is surgical removal as per guidelines.’
 
Supporting Associate Professor Hudson’s point is the fact that in addition to those unlikely to die from melanoma, the researchers also found a small subset of high-risk patients who had a mortality risk in excess of 20%.
 
Australia has the highest rate of melanoma in the world, recording 1300 deaths from the approximately 16,800 people diagnosed each year. But this prevalence has also helped position it as a world leader in terms of treatment – in the past decade alone, 50-year survival rates nationwide have increased from below 10% to over 50%.
 
‘Australia … leads the gold standard in detection. Most melanomas are diagnosed by GPs, with Queensland GPs diagnosing the earliest melanomas on average,’ Associate Professor Hudson said.
 
‘Everyone currently needs their melanoma removed, but what this study shows is that the current American system – where all T1b [0.8–1 mm Breslow] melanomas get sentinel lymph node biopsy – can have further subtlety with its application based on demographics and tumour features.
 
‘We are already doing this in Australia using Australian-based data and software such as the melanoma nomogram, which unlike the American study incorporates mitotic rate, and I’d highly recommend its use for GPs.’
 
Meanwhile, ongoing research into genetics and molecular medicine may help further refine future management options and may even determine which melanomas can be treated differently.
 
Associate Professor Hudson also says there are emerging trends using artificial intelligence for early diagnosis, and that a lot of good work is already being done in Australia, with primary care being shown to be particularly effective and cost efficient.
 
‘We are [predicted] to have a large increase in melanomas by 2030, with general practice expected to take the majority of this work,’ he said.
 
‘Research and policy is still done with a focus on tertiary centres and I’d like to see greater incorporation and support for GPs. Some GPs do an amazing job working long hours as well as generating research.
 
‘Given appropriate support, we can achieve great things with collaborative research with other specialisations.’
 
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