Repair of UV Light-Induced DNA Damage and Risk of Cutaneous Malignant Melanoma.

Background: The mechanism underlying the role of UV light exposure from sunlight in the etiology of cutaneous malignant melanoma (CMM) is unclear. Patients with xeroderma pigmentosum, a disease characterized by severe sensitivity to UV radiation and a defect in nucleotide excision repair, have a high incidence of CMM, which suggests that DNA repair capacity (DRC) plays a role in sunlight-induced CMM in the general population as well. Methods: We conducted a hospital-based case-control study of DRC and CMM among 312 non-Hispanic white CMM patients who had no prior chemotherapy or radiation therapy, and 324 cancer-free control subjects who were frequency-matched to case patients on age, sex, and ethnicity. Information on demographic variables, risk factors, and tumor characteristics was obtained from questionnaires and medical records. We used the hostcell reactivation assay to measure the DRC in study subjects' lymphocytes. All statistical tests were two sided. Results: Case patients had a 19% lower mean (± standard deviation [SD]) DRC (8.5 ± 3.4%) than control subjects (10.5 ± 5.1%), a statistically significant difference (P < .001). DRC that was at or below the median value (i.e., 9.4%) in control subjects was associated with increased risk for CMM after adjustment for age, sex, and other covariates (odds ratio [OR] = 2.02, 95% confidence interval [CI] = 1.45 to 2.82). We observed a dose-response relationship between decreased DRC and increased risk of CMM (P[sub trend] < .001). Patients with tumors on sun-exposed skin had statistically significantly lower DRC than patients with tumors on unexposed skin (8.2 ± 3.3% versus 9.5 ± 3.5%; P = .004). Conclusions: Reduced DRC is an independent risk factor for CMM and may contribute to susceptibility to sunlight-induced CMM among the general population. [ABSTRACT FROM AUTHOR]