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Radiation Exposure Affects Non-melanoma Skin Cancers

December 21, 2007

A report, 'Squamous cell and basal cell carcinoma of the skin in relation to radiation therapy and potential modification of risk by sun exposure,' has been recently published in Epidemiology (2007;18(6):776-84). "Epidemiologic studies consistently find enhanced risk of basal cell carcinoma of the skin among individuals exposed to ionizing radiation, but it is unclear whether the radiation effect occurs for squamous cell carcinoma. It is also not known whether subgroups of individuals are at greater risk, eg, those with radiation sensitivity or high ultraviolet radiation exposure," researchers at Norris Cotton Cancer Center report.

"We analyzed data from a case-control study of keratinocyte cancers in New Hampshire. Incident cases diagnosed in 1993-1995 and 1997-2000 were identified through a state-wide skin cancer surveillance system, and controls were identified through the Department of Transportation and Center for Medicare and Medicaid Service Files. We found an association between history of radiation treatment and basal cell carcinoma. The association was especially strong for basal cell carcinomas arising within the radiation treatment field, and among those treated with radiation therapy before age 20, those whose basal cell carcinomas occurred 40 or more years after radiation treatment, and those treated with radiation for acne.

"Similar age and time patterns of risk were observed for squamous cell carcinoma, although generally with smaller odds ratios. For basal cell carcinoma, early exposure to radiation treatment was a risk factor largely among those without a history of severe sunburns, whereas for squamous cell carcinoma, radiation treatment was a risk factor primarily among those with a sun-sensitive skin type (ie, a tendency to sunburn). Radiation treatment, particularly if experienced before age 20, seems to increase the long-term risk of both basal and squamous cell carcinomas of the skin," wrote M.R. Karagas and colleagues, Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center.

The researchers concluded: "These risks may differ by sun exposure or host response to sunlight exposure."