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Dermatopathology: Practical & Conceptual January - March 2008
3. New Heights: Ultraviolet radiation is not the chief cause of basal-cell carcinoma!
Roni Dodiuk-Gad, M.D.
A. Bernard Ackerman, M.D.
“Evidence” on behalf of UVR being chiefly responsible for basal-cell carcinoma (A) and refutation of that “evidence” (B)
Deficiencies serious in the methodology of studies pertinent to UVR and the supposed relationship of it to basal-cell carcinoma:
Evidence on behalf of genetic factors being crucial to development of basal-cell carcinoma:
Exogenous factors capable of inducing basal-cell carcinoma:
Most textbooks of dermatology attribute basal-cell carcinoma (BCC) chiefly to ultraviolet radiation (UVR), especially that from the sun, but without providing any evidence convincing of the relationship purported. Representative of that phenomenon are the statements that follow:
"There is persuasive evidence that each of the three main types of skin cancer, BCC, SCC and melanoma is caused by sun exposure."
(Armstrong, 2001) [
"The prime etiological factor in the development of basal cell carcinoma is exposure to UV."
(Weedon, 2002) [
"Chronic overexposure to sunlight is the cause of 95 percent of all basal cell carcinomas."
(Turkington, 2002) [
"Exposure to ultraviolet radiation is the main causative factor in the pathogenesis of basal cell carcinoma."
(Wong, 2003) [
"UVR is now recognized as by far the most important and best understood risk factor for [non-melanoma skin cancer] development."
(Mackie, 2004) [
"In the development of BCC in the skin, sunlight exposure is the most important causative factor."
(Bae, 2005) [
"It is an undisputed fact that the main risk factor for nonmelanoma skin cancer is directly related to ultraviolet exposure."
(Petrou, 2006) [
"The etiologies of skin cancer are multiple . . . the most important exogenous factor is UVR from sunlight."
(Mehrany, 2007) [
Some authors, however, have called into question the reputed link between UVR and BCC. [
] This is how they expressed it:
"In this study we were able to assess individual cumulative exposures to UVB form the first time . . . previous studies used indirect measures of UVB."
"One important finding in our study that needs to be investigated further is the failure to find an association between UVB exposure and BCC. If in fact UVB is important in the occurrence of BCC, our study group should have had more BCC cases then observed because clearly there was sufficient UVB dose to induce BCC development . . . The carcinogenic effect of UV exposure differs significantly between BCC and SCC. Because of this, in future epidemiologic and biologic research on nonmelanoma skin cancer, SCC, and BCC should be investigated separately."
"The direct evidence linking sun exposure and skin cancer is weak with few well-conducted studies of sun exposure in individuals. Mostly, studies of total sun exposure have not found statistically significant positive associations...many questions remain about the relationship between sun exposure and skin cancer."
"The lack of association between relative UVR exposure on the eyelids and BCC location indicates that UVR exposure only partially explains the aetiology of periorbital BCC, and there are probably other, yet unidentified, factors that contribute to the development of these tumours."
(Lindgren, 1998) [
"We assessed potential risk factors for BCC . . . indexes of sun exposure for both recreational and occupational purposes gave inconclusive results."
(Naldi, 2000) [
"Site-specific cumulative UV exposure alone is a poor predictor of frequency or histologic features of BCC."
(Heckmann, 2002) [
"Sun exposure only partly explains the etiology of periorbital BCC."
(Erbagci, 2003) [
"The relationship between the cumulative dose of UV and the development of BCCs is still controversial."
(Zak-Prelich, 2004) [
In the following we will assess the "evidence" (A) on behalf of UVR being chiefly responsible for basal-cell carcinoma and we will present refutation (B) of that "evidence."
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