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Higher vitamin D levels linked to risk for basal cell carcinoma

Last Updated: 2010-01-18 11:45:12 -0400 (Reuters Health)

January 19, 2010

NEW YORK (Reuters Health) - Even years after measurement, high serum levels of vitamin D (25(OH)D) are associated with an elevated risk of basal cell carcinoma, findings from a nested case-control study suggest.

According to the report in the December 31 advanced online issue of the Journal of Investigative Dermatology, "The same spectrum of UV radiation causes both DNA damage to keratinocytes and vitamin D synthesis by these cells."

This could mean that "vitamin D formation in keratinocytes may be an innate protective mechanism against UV damage," according to the authors. On the other hand, they add, in vitro and in vivo evidence suggests that vitamin D and its receptor are involved in cutaneous carcinogenesis.

But until now, no one has directly examined the relationship between serum vitamin D levels and basal cell carcinoma in humans.

Lead author Dr. Maryam M. Asgari and colleagues did just that, using a Kaiser Permanente electronic database of pathology specimens of basal cell carcinomas. The pathology reports were matched with data on each patient's serum level of 25(OH)D before the skin cancer developed.

In the 220 Caucasian patients and 220 controls, 25(OH)D had been measured between 1968 and 1970. Cancer cases were diagnosed between 1974 and 1979. The mean time between measurement and diagnosis was 8.74 years.

Dr. Asgari, from Kaiser Permanente Northern California, Oakland, and her team found that for every 1 ng/mL rise in serum 25(OH)D levels, the risk of basal cell carcinoma rose by 3%. For subjects with levels in the highest quintile, the unadjusted odds ratio was 2.32 compared with the lowest quintile (p = 0.03 for trend).

Moreover, individuals who had clinically sufficient 25(OH)D levels (at least 30 ng/mL) were at significantly increased risk compared with those who were deficient (< 10 ng/mL), with an unadjusted odds ratio of 3.98 (p < 0.01).

In multivariate analysis adjusted for body mass index, smoking status, education, estimates of sun exposure, X-ray exposure, and personal history of cancer, the risk of basal cell carcinoma rose by 2% with each ng/mL increase in 25(OH)D. Comparing sufficient with deficient levels still yielded an adjusted odds ratio of 3.61 (p = 0.03).

This analysis was limited by the use of surrogates for sun exposure (e.g., leisure time activities, occupation), none of which was associated with levels of serum 25(OH)D or a significant risk factor for basal cell carcinoma, the authors note. Moreover, the model did not take into account variables such as supplemental vitamin D use or healthcare screening bias.

"Future studies that can accurately measure acute and intermittent sun exposure, supplemental vitamin D use, and other potential confounding factors may be warranted," the research team concludes.

J Invest Dermatol 2009.

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