Table 1

 Summary of studies included in the meta-analysis

Connell14Farrell15Fraser16Kinlen12Korelitz17Lewis1
IBD, inflammatory bowel disease; UC, ulcerative colitis; CD, Crohn’s disease; NHL, non-Hodgkin lymphoma; HD, Hodgkin’s disease; AZA, azathioprine; 6-MP, 6-mercaptopurine; 95% CI, 95% confidence interval.
*Treated with immunomodulators.
†Two additional lymphomas observed in patients treated with methotrexate and ciclosporin.
N/R, not reported.
‡SIR, standardised incidence ratio for lymphoma. Because of rounding of the expected number of lymphomas, SIR does not exactly equal observed number of lymphomas divided by expected number of lymphomas.
Year199420002002198519992001
SettingSingle centreSingle centreSingle centreSingle centreSingle centrePopulation based
Total No of IBD patients755238*6263214861465
    % with CD604643N/R6757
    % with UC405457N/R3343
Mean/median duration of treatment12.5 mo1.82 y2.26 yN/R4.4 y2 y
Medication studiedAZAAZAAZAAZA6-MPAZA
Mean/median dose or range2 mg/kg/day2–2.5 mg/kg/day1.65 mg/kg/dayN/R12.5–100 g/day106 mg/day
Mean/median duration of follow up9 y6.9 y6.9 yN/R5.9 y2.87 y
OutcomeNHLNHLNHL and HDNHLNHL and HDNHL and HD
Expected No of lymphomas0.520.050.650.160.610.64
Observed No of lymphomas02†3231
SIR‡ (95% CI)0 (—)37.5 (3.5–137.7)4.6 (0.9–13.7)12.5 (1.2–46.0)4.9 (0.9–14.5)1.6 (0.0006–9.0)