Table 2 Factors associated with significant difference favouring experimental treatment^*

Independent variable Adjusted odds ratio (95% CI) P value End point: Overall survival Reference Other time to event 4.7 (1.8 to 12.7) 0.008 Response rate 2.8 (0.8 to 9.5) Data protocol closed to recruitment: 1981-5 Reference 1986-90 4.4 (1.6 to 12.1) 0.009 1991-5 1.7 (0.5 to 5.5) Type of malignancy: Advanced solid tumour Reference Haematological 1.9 (0.7 to 5.0) 0.015 Locoregional solid tumour 5.8 (1.8 to 19.0)

^* Results of logistic regression model evaluating attributes of randomisations in which compared with control arm, experimental arm met statistical criteria for superiority defined in protocol.

Some randomisations report more than one two way comparison of experimental to control arm. Model therefore uses clustering by randomisation to adjust for lack of independence within randomisations.

Use of placebo/observation control and number of patients per arm were not associated with significant difference in favour of experimental arm.