A quick update on skin cancer screening and melanoma incidence
Fewer people had skin cancer checks in 2020, due to the COVID response. What impact has this had on melanoma diagnoses?
Back in January, I wrote an article, Skin cancer checks: life-saver or scam? about a paper which found that the biggest risk factor for a diagnosis of melanoma was not sunshine exposure, but the number of doctors conducting skin checks in your area.
The authors’ summary of their findings is quite startling for those who’ve bought into the sunlight-gives-you-cancer narrative:
“In this cross-sectional ecological study of 727 US counties, melanoma incidence was weakly (or unexpectedly negatively) correlated with proxies for UV radiation exposure and was more strongly (and consistently positively) associated with proxies for diagnostic scrutiny.”
That paper drew on melanoma incidence reporting to the Surveillance, Epidemiology, and End Results (SEER) Program covering the period from 2012 to 2016. What has happened to melanoma diagnoses since then?
Well, you might remember this little thing that happened in 2020, when the attention of the entire medical profession and (so-called) health system became myopically focussed on a teeny-tiny virus called SARS-CoV-2 that caused a flu-like illness with an infection fatality rate of 0.07 per cent (that’s 7 deaths per 10 000 infections, for the mathematically challenged) in people under the age of 70. Go on, search your memory banks. I’m sure you’ll be able to recall it.
You might also recall many doctors expressing grave concerns about missed diagnoses that might occur while doctors were too scared to see patients in person. Missed cancer diagnoses were high on their list, because of the widely-held belief that ‘catching cancer early’ through screening and other early detection programs reduces death rates, because early-stage cancer is easier to treat.
While this belief makes intuitive sense, it is almost certainly wrong, as I explained in Major trial finds screening colonoscopy fails to ‘save lives’:
“H. Gilbert Welch uses the ‘barnyard pen of cancers’ analogy to characterise the highly heterogeneous grab-bag of diagnoses collectively labelled ‘cancer’, into three types of animal, with the fence representing screening:
‘Birds’ represent the most lethal type of cancer. No fence can contain them; they simply fly away. By the time ‘bird’ cancers are detected, they’ve already spread around the body, invading vital organs. Conventional cancer treatments hold no hope of cure; at best, life may be prolonged by surgery, chemotherapy, radiation or immunotherapy, but at the cost of side-effects that dramatically reduce quality of life.
‘Rabbits’ could be contained if you build enough fences. Catching ‘rabbits’ is the mainstay of cancer screening. This would be worthwhile if ‘rabbit’ cancers would have gone on to cause life-threatening illness if they had not been detected, but research indicates that this is rarely the case. In the small minority of people in whom screening caught a ‘rabbit’ that would have gone on to kill them, detecting it early would only be of benefit if the treatments for that cancer type were effective at curing it, and did not cause harms that outweigh their benefits. By the time we apply all these criteria, we’re in unicorn land.
‘Turtles’ can easily be contained by fencing, but since they weren’t going anywhere anyway, there’s no point in putting the effort into building the fence.
It’s the ‘turtles’ and ‘rabbits’ that are most likely to be detected by cancer screening. Hence, cancer screening results in considerable overdiagnosis – that is, many people are told that they ‘have cancer’, and undergo aggressive treatment which may lead to lifespan-shortening health problems (including, ironically enough, cancer), for a tumour which would never have led to serious illness or death if it had remained undetected.”
Back to melanoma. Just last week, JAMA Dermatology published a research letter on melanoma incidence in the US in 2020, using data from the same SEER program as used in the earlier article.
The authors were prompted to conduct their analysis by two other papers that “reported an increased relative proportion of advanced melanomas in the US during the COVID-19 pandemic”. That is, these studies claimed that a higher percentage of melanomas were diagnosed at a point where they were more severe and potentially life-threatening, implying that interruption of skin checks during the manufactured COVID crisis had delayed the diagnosis of melanoma, endangering the lives of those who would otherwise have been diagnosed at an earlier stage.
However, analysis of SEER data revealed that only the incidence of stage 1 melanoma (i.e. the earliest, least deadly form) decreased during 2020, while diagnoses of more advanced stages stayed steady. In other words, there was a higher proportion of diagnoses of advanced melanoma in 2020, but the rate was unchanged. In addition, there was no drop in diagnosis of the most common subtype of melanoma in darker skinned populations, acral lentiginous melanoma:
“Incidence rates of superficial spreading melanomas, which are associated with screening, significantly decreased during the pandemic, but acral lentiginous melanoma incidence rates were stable. Similarly, the largest incidence decreases were seen in early-stage and less aggressive melanomas… The relative increase in thick melanomas in 2020 was primarily associated with a marked decrease in thin melanomas, rather than an absolute increase in thicker melanomas.”
The (often dramatic) difference between relative and absolute risks, and relative and absolute risk reduction, is something that I really hammered during my recent Be Your Own Doctor seminar, which you can access here. Grasping this difference is crucial to making informed healthcare choices.
The authors of the research letter acknowledge that it’s too early to tell whether the decline in diagnosis of stage 1 melanoma during the manufactured COVID crisis will impact on the outcome of most concern – the development of potentially life-threatening cancers. There are two possibilities: One is that the interruption of screening for skin cancer in 2020 mostly reduced the overdiagnosis (and subsequent overtreatment) of people whose melanomas were never going to cause much trouble anyway. The other possibility is that many melanomas with life-threatening potential were missed at a stage when they would have been easily treatable, and hence, we will see an increased incidence of advanced melanoma in the years to come:
“If the pandemic primarily influenced diagnosis of indolent early melanomas, the incidence of thick melanoma should increase slightly in 2021 due to missed cases from 2020 subsequently being diagnosed, assuming a stable annual incidence of thick melanomas. However, if the pandemic played a role in missed diagnoses of thin melanomas that progressed to thick melanomas, a substantial future increase in thick melanoma incidence would be expected.”
Unfortunately, data on US melanoma mortality in the post-COVID period are not yet available. However, comparing the American Cancer Society’s estimates of melanoma mortality for the years 2020-2023 (which are based on projections from previous years’ death data) don’t suggest that there has been a sudden surge of deaths from missed melanoma diagnoses that were treatable ‘rabbits’. The ACS estimates the number of melanoma deaths in 2020 at 6850, 2021 at 7180, 2022 at 7650 and 2023 at 7990. Meanwhile, the population has swelled from 331,449,281 in April 2020 to 340,370,140 at the time of writing this article. So far, no apparent tsunami of melanoma deaths.
The final sentence of the research letter is a stellar example of the type of understated language that scientists use when they’re trying to persuade people to stop doing dumb things, without offending anyone:
“Longer-term studies are needed to examine the implications of the pandemic for melanoma incidence and may help inform screening and overdiagnosis efforts.”
Translation: The temporary pause in skin checks that occurred in 2020 should be closely tracked. If there is no rise in the incidence of advanced melanoma, or deaths from melanoma, this will provide strong evidence that actively searching for melanoma through screening programs increases the number of people who are unnecessarily diagnosed with cancer and shunted down a treatment pipeline that causes them net harm.
As emphasised in my previous articles on overdiagnosis of cancer, screening is not the same as diagnosis. If you notice a skin lesion that is rapidly growing, changing colour, causing you pain or irritation, or behaving in any other fashion that causes you concern, get it checked by a competent doctor (preferably one who doesn’t make a sizeable chunk of their income from diagnosing and treating such lesions).
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