Dermatology itself slammed the Mayo Clinic’s one-county skin cancer registry as not representing the rest of the nation — a point many in the American news media did not pick up on Monday when reports about Mayo’s latest one-county skin cancer study made national headlines.

Mayo on Monday alleged that melanoma in women 18-39 increased eight-fold in Olmsted County, Minn., from 1970-2008 — a finding that is not consistent with national data, which show a decrease in mortality in that age group and in increase in incidence that simply matches the increase in the number of dermatologists per capita nationwide. Mayo also alleged their registry is somehow more accurate than the National Cancer Institute’s much-larger national registry and that indoor tanning is to blame for the alleged increase, even though the data-set does not have any information on indoor tanning.

Simply put: There was no way to know if any of the 256 patients in Olmsted County who had melanoma over the 40-year-period of Mayo’s study ever used a sunbed at all.

But now it turns out the same data-set used to create Mayo’s unfounded attack on indoor tanning Monday was actually attacked in a published journal article in 2006 by the dermatology industry itself, which said Mayo’s assertions from the same one-county data set could not be applied on the national level. In a peer-reviewed study published in the journal Dermatologic Surgery, researchers from The Center for Dermatology at the Wake Forest University School of Medicine questioned Mayo’s 2005 assertion that non-melanoma skin cancer was increasing in women under age 40.

“Our results indicated that there is no significant increase in the incidence of non-melanoma skin cancer among patients younger than 40 years in the United States,” the Wake Forest group wrote. “Further, findings that young women were at higher risk for NMSC were not confirmed at national level.” The Wake Forest group looked at doctor visits logged nationwide from 1979-2003.

Smart Tan pointed out on Monday that Mayo failed to disclose that Olmsted County has 15 times more dermatologists per capita than the national average — a huge disparity which fully explains: (1) why that county’s database is detecting more skin cancers, (2) why the alleged increase is only in the thinnest, almost-always-benign lesions and (3) why the mortality rate in that age group actually dropped over the same period.

It is statistically impossible for incidence of a disease to increase if mortality is decreasing. While Mayo told the American media yesterday that better detection lowered the death rate, that explanation is ridiculous, according to those who follow cancer statistics. (Click here to read “Overdiagnosis in Cancer” from the National Cancer Institute).

“The 2006 Mayo paper, and the subsequent criticism of that dataset, raise even more questions about the accuracy of Monday’s Mayo paper,” Smart Tan Vice President Joseph Levy said. “Mayo Dermatology appears to be hiding information that conflicts with its statements. That’s not science. It’s politics.”

Smart Tan will continue to report on the Mayo paper.

Click here to read the Smart Tan response to the Mayo paper.

Click here to read the Wake Forest critique of the 2005 Mayo paper.