SIR stratified according to treatment category*
| Treatment† | Patients (n) | SIR (95% CI)‡ | SIR p Value‡ | Cyclophosphamide cumulative dose (g), mean (SD)§ | Follow-up (years), mean (SD)¶ | Organ involvement, mean** |
|---|---|---|---|---|---|---|
| Only cyclophosphamide | 119 | 3.10 (2.06 to 4.48) | <0.001 | 7.26 (4.94) | 4.92 (3.10) | 2.11 (1.49) |
| Only rituximab | 41 | 0.67 (0.08 to 2.43) | 0.86 | 0.00 | 6.34 (3.56) | 2.35 (1.09) |
| Both | 114 | 1.01 (0.46 to 1.93) | 1.00 | 11.05 (11.63) | 6.60 (2.84) | 2.56 (1.63) |
| None | 48 | 2.10 (0.77 to 4.56) | 0.14 | 0.00 | 4.20 (2.94) | 1.96 (1.44) |
*Values are reported as means (SD) unless otherwise indicated. The SIR is the ratio of the observed to expected malignancies adjusted for sex, age (per 5-year age group) and calendar time period (per 1-year calendar time period).
†The ‘only cyclophosphamide’ group was treated with cyclophosphamide but not with rituximab. The ‘only rituximab’ group was treated with rituximab but not with cyclophosphamide. ‘Both’ indicates a group that received cyclophosphamide and rituximab. ‘None’ indicates a patient group that neither received cyclophosphamide nor rituximab, but instead had various heterogeneous treatments including glucocorticoids, azathioprine, mycophenolate mofetil and methotrexate. Other immunosuppressive drugs were also administered in all of the groups.
‡Calculated by exact Poisson regression analysis.
§The mean cumulative cyclophosphamide dose differed between the ‘only cyclophosphamide’ and ‘both’ groups (Student's t-test, p=0.002).
¶The mean follow-up duration differed between groups (ANOVA, p<0.001). The mean follow-up duration also differed when the ‘only rituximab’ and ‘both group’ were compared with the ‘only cyclophosphamide’ and ‘none’ group (Student's t-test, p<0.001).
**The mean organ involvement did not differ between groups (ANOVA, p=0.07).
ANOVA, analysis of variance; SIR, standardised incidence ratio.