Basal Cell Carcinoma in United States Radiologic Technologists
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Date
2014-06-13
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Johns Hopkins University
Abstract
Abstract
Background: High doses of ionizing radiation (IR) are a known risk factor for basal cell carcinoma (BCC). Few studies have analyzed protracted low doses of IR exposure (<100 mGy)
and excess BCC risk, and important factors such as ultraviolet radiation (UVR) exposure and anatomic location of BCCs have not been included in these studies.
Objective: To determine risk for incident BCC from cumulative low dose IR in US radiologic technologists, with adjustment for potential confounders; and to examine potential effect modifiers.
Methods: In a prospective cohort study design, we studied 65,719 cancer free technologists who answered at least two questionnaires between 1983 and 2008. We used Cox proportional hazards and Poisson regression models. We also assessed risk by sun-exposed versus sun-
shielded anatomic tumor location.
Results: The cumulative mean absorbed dose (to the skin of the head, neck and arms) was 55.8 mGy (maximum: 1,735 mGy). There was no evidence of an association between cumulative IR dose and BCC; the multivariate adjusted excess relative risk per Gy (ERR/Gy) was -0.01 (95% CI: -0.43, 0.52); although depending on the age-adjustment used, some models yielded significant increasing trends with dose. Exposure which occurred under age 30 was associated with a statistically significant increased BCC risk (ERR/Gy = 0.78; 95% CI: 0.09, 1.61) adjusted by gender and age, with lower risk at older ages (likelihood ratio test p=0.006); multivariate adjustment (including host factors and sun exposure) did not materially affect the results. Exposure in earlier decades (before 1960) was associated with a dose-related increased risk (p<0.001), although cautious interpretation is warranted considering the unusually high estimates. There was no significant modifying effect of time since exposure. There was no difference in radiation-associated risk by sun-exposed compared to sun-shielded skin.
Conclusions: Consistent with expectation, there was evidence that low dose occupational IR
exposure at younger ages was associated with excess risk for BCC, with lower risk for exposures at older ages. We found no evidence of effect modification by sun exposure. Because of large uncertainties in dosimetry and sensitivity to model specification, these findings should be interpreted with caution.
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Keywords
Basal Cell Carcinoma, Ionizing Radiation, Occupational Health