Skin cancer: An epidemic or case of better diagnosis?

Posted on Jul 9, 2015 in Medical Rewind

Listen to what Dr. Rashid A. Buttar and Robert Scott Bell have to say about this article on the May 25th Medical Rewind Show

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Skin cancer continues to be diagnosed worldwide at a faster rate than any other major cancer. But does a rise in the number of melanoma cases indicate an epidemic or are doctors more aggressively diagnosing precancerous skin lesions as melanoma?

Vancouver dermatologist Dr. Jason Rivers, and Dr. Darrell Rigel, a dermatologist from New York, say the melanoma epidemic is real as data shows the number of cases steadily climbing in many countries, However, Dr. Earl Glusac, who specializes in dermatopathology in New Haven, CT., argues that epidemic is an illusion, created by increased skin cancer screening.

He cautions that overdiagnosis of melanoma could lead to unnecessary anxiety, as patients may believe they are going to die from cancer when they may not.

The three top specialists debated the decade-old controversy on the final day of the 2015 World Congress of Dermatology, which began June 8 and wrapped up Saturday at the Vancouver Convention Centre.

Melanoma is a malignant (meaning it can spread or metastasize) tumour that starts in melanocytes, a type of cell that makes the pigment melanin. Cells in the skin sometimes change and cause non-cancerous, or benign, tumours such as dermatofibromas, epidermal cysts or moles (also called nevi.)

But changes can also cause cancer. When melanocytes change and become abnormal, they can cause precancerous conditions. This means that the cells are not yet cancer but there is a higher chance these abnormal changes may become cancer, according to the Canadian Cancer Society.

An atypical mole, or dysplastic nevus, is a precancerous condition of the skin that is more likely than ordinary moles to develop into melanoma, the society says.

Glusac’s argument against a melanoma epidemic rests largely on a study by Dr. H. Gilbert Welch, whose research, which was published in the British Medical Journal in 2005, showed that skin biopsies rose by 250 per cent since 1986, but there was no change in the melanoma death rate or the incidence of advanced disease.

“Are we doing a great job stamping out melanoma or are we overdiagnosing? Overdiagnosis is the diagnoses of disease that will never cause symptoms or death,” Glusac said to members of the Congress.

Welch argued that if there was an epidemic of melanoma, scientists should see increases in cancers at all stages.

“With Lung cancer mortality went up along with incidents, and that’s what was expected in an epidemic of cancer,” said Glusac.

He questioned whether doctors are applying the same criteria to thin lesions as thick lesions. In the past, he said physicians didn’t sample anything smaller than a nickel, but now they are sampling lesions smaller than an aspirin.

He also argued the fear of error is contributing to the rise.

A skin cancer lesion the size of pea could kill a patient, while a lesion of similar size in the breast, colon or thyroid, if removed, is generally cured, he said.

“So there is a tremendous incentive not to miss a melanoma.” But some melanomas look like nevus, and so many doctors are overdiagnosing nevus as melanoma.”

This leads to what he called a “reservoir of pseudo-malignant disease.” He compared the reservoir to how prostate PSA screening is leading to more men being treated for tumours deemed malignant but with a very low risk of malignancy. In some cases, treatment for prostate cancer can lead to incontinence and impotence.

“Unfortunately, melanoma is like prostate cancer. The harder you look for it, the more you screen for it, the more you biopsy it, the more you seem to find it, but without the morbidity and mortality,” he said.

A melanoma diagnosis can cause significant problems with insurance, anxiety, fear, and lead people to make tough life decisions, such as not having any more children, Glusac said.

But Rivers and Rigel said early detection and screening remains the best defence in lowering mortality, and argue that because melanoma can be so deadly, the best practice is to remove melanomas before they spread.

“I agree there is a reservoir of cases out there, but the reality is the incidents of thick melanomas are still rising,” said Rigel.

Rivers said there are more than two million cases of skin cancer diagnosed in the U.S. each year, with 73,000 of those new cases of melanoma. He added that every hour someone dies from melanoma in North America,

“Can you tell which melanoma is going to kill and not kill? I can’t,” said Rivers.

The rate of melanoma has climbed to 26 people per 1,000 population from 18 over 20 years in the U.S. The rates are going up and there is an increase among young women, which Rivers noted has been linked to indoor tanning.

Rivers also presented data from Canada, England, France, Norway, Finland and Australia, where overall the number of melanoma cases have gone up over the past decade. Though he said rates of melanoma are rising rapidly in older populations and slowing among younger people between ages 15 and 24, presumably because of public education about skin cancer.

“Let’s face it if there was an increase of overdiagnosis, then we should see this in all age groups and not just older groups,” said Rivers.

Source:  Vancouver Sun