title: Use of thiopurines in the treatment of inflammatory bowel disease is associated with an increased risk of non-melanoma skin cancer in an at-risk population: a cohort study.
abstract: OBJECTIVE
  The thiopurines azathioprine and 6-mercaptopurine are effective in the management of patients with inflammatory bowel disease (IBD) in whom aminosalicylates, antibiotics and corticosteroids have failed to induce or maintain remission. Long-term use of these agents has been linked to a greatly increased risk of non-melanoma skin cancer and lymphatic cancer in organ transplant recipients. There is some evidence to suggest that IBD patients receiving thiopurines might be at increased risk of cancer. Our aim was to determine the incidence of cancer in a cohort of patients with IBD managed in our clinic, and to relate this to thiopurine exposure.
  
  
  METHODS
  We conducted a retrospective study based on the clinical and pathology records of patients attending a specialist IBD clinic at Groote Schuur Hospital, Cape Town, South Africa between 1960 and 2007.
  
  
  RESULTS
  We analyzed the records of 1084 patients. A total of 123 subjects (11.5%) had received thiopurine therapy. Cancer was identified in 51 patients (4.7%), including colorectal cancer (15 patients), melanoma (two patients), non-melanoma skin cancer (seven patients) and non-Hodgkin's lymphoma (five patients). A diagnosis of non-melanoma skin cancer was significantly associated with thiopurine exposure (odds ratio 5.0, 95% confidence interval 1.1-22.8). Six of seven non-melanoma skin cancers occurred in Caucasian patients, with a highly significant association with thiopurine use (odds ratio 12.4, 95% confidence interval 2.3-67.4).
  
  
  CONCLUSIONS
  Patients with IBD who receive thiopurines are at increased risk of non-melanoma skin cancer. The risk is highest in Caucasian patients, and is negligible in other groups.
authors.affiliation: Division of Gastroenterology, Department of Medicine, University of Cape Town, South Africa.
authors.forename: Mashiko
authors.initials: M
authors.lastname: Setshedi
authors.forename: David
authors.initials: D
authors.lastname: Epstein
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Winter
authors.forename: Landon
authors.initials: L
authors.lastname: Myer
authors.forename: Gillian
authors.initials: G
authors.lastname: Watermeyer
authors.forename: Richard
authors.initials: R
authors.lastname: Hift
mesh_terms: D000328:Adult; D000893:Anti-Inflammatory Agents / Q000009:adverse effects*; D001379:Azathioprine / Q000009:adverse effects*; D005260:Female; D005765:Gastrointestinal Agents / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy* / Q000208:ethnology; D008297:Male; D015122:Mercaptopurine / Q000009:adverse effects*; D008875:Middle Aged; D016017:Odds Ratio; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012878:Skin Neoplasms / Q000139:chemically induced* / Q000208:ethnology; D012880:Skin Pigmentation; D013019:South Africa / Q000453:epidemiology; D013472:Sunlight / Q000009:adverse effects; D013997:Time Factors; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D000893:Anti-Inflammatory Agents; D005765:Gastrointestinal Agents; D015122:Mercaptopurine; D001379:Azathioprine