Early studies of patients with IBD reported conflicting results regarding the risks for NMSC and the importance of immunosuppressive medications.

One series of IBD patients reported increasing risks of NMSC, but immunosuppression as a causative factor was not specifically evaluated.7,8 In contrast, a prospective cohort study did not find an increase in skin cancer incidence in patients with ulcerative colitis.9 More recent epidemiological studies Selleckchem R788 continue to report contradictory results: Long and colleagues found that recent and ongoing exposure to thiopurines was associated with increased risk of NMSC,10 while a Dutch study of 2887 patients reported that thiopurine use was not associated with increased risk of NMSC.11 A recent meta-analysis, which included a number of population-based studies consisting of IBD patients on thiopurines, reported an overall increased incidence of NMSC.12 This is supported

by a CESAME study from France, which prospectively studied a cohort of nearly 20 000 patients over a median period of 35 months and showed that ongoing thiopurine treatment (hazard ratio, 5.9; 95% confidence interval, 2.1–16.4, P = 0.0006) and past thiopurine exposure (HR, 3.9; 95% CI, 1.3–12.1, P = 0.02) were risk factors for NMSC.13 This study also found that drug-induced immunosuppression selleck chemical reverses the ratio of squamous-cell to basal-cell carcinoma. In this issue of Journal of Gastroenterology and Hepatology,14 Shetsedi and colleagues retrospectively reviewed records of IBD patients between 1960 and 2007 and concluded that patients with IBD who receive thiopurines are at increased risk of NMSC; further, the risk is highest among Caucasian patients. This study was conducted in Cape Town, South Africa, a place with high incidence of skin cancers. However the majority in the study were of mixed ethnicity. Out of a total cohort of 1084, 11% of patients were on thiopurines; the duration of thiopurine exposure and the temporal relationship between

thiopurine use and diagnosis of NMSC was not explored. Interestingly this study did not find the known increased aminophylline risk of lymphoma among those treated with thiopurines that has been found in other bigger studies. However, the results of the present study do confirm the findings of the recent largest prospective CESAME cohort,13 that NMSC is increased with immunosuppression. An understanding of the “photobiology” of thiopurines helps explain the increased risk of non-melanotic skin cancer, while the risk of solid cancers other than lymphoma may be reduced.15 The major components of the ultraviolet spectrum are UVB (wavelength 280–320 nm) and UVA (320–400 nm) light; visible light is above 400 nm. The carcinogenic effects of UV radiation are mainly attributable to UVB,16 which can cause direct DNA damage and is responsible for sunburn.