The number needed to treat for adalimumab, etanercept, and infliximab based on ACR50 response in three randomized controlled trials on established rheumatoid arthritis: a systematic literature review

Objective: To compare the efficacy of adalimumab, etanercept, and infliximab in patients with established rheumatoid arthritis (RA) taking concomitant methotrexate (MTX) by calculating the number needed to treat (NNT) using three different methods. Methods: A systematic literature search of the Cochrane Library, MEDLINE, and EMBASE was conducted from inception to 30 June 2006. Two pairs of investigators, a Danish and a Swedish pair, independently conducted a structured literature review. The reviewers selected any published randomized, double-blind, MTX controlled study of adalimumab, etanercept, and infliximab, presenting the American College of Rheumatology 50% response (ACR50) after 12 months in RA patients with a mean disease duration of at least 5 years. The two review groups independently extracted the estimates necessary to calculate the NNT. Results: The reviewers consistently selected the same three randomized, controlled trials (RCTs), one for each of the drugs, and extracted equal data for the number of patients completing the 12-month intervention, and the corresponding number of ACR50 responding patients after therapy. Some baseline differences were noted: patients in the etanercept trial had a shorter disease duration and did not receive MTX prior to inclusion; patients in the adalimumab study had lower Health Assessment Questionnaire (HAQ) scores. The calculated NNTs varied slightly depending on the method used. The fully adjusted NNTs (95% confidence intervals) for adalimumab, etanercept, infliximab standard dosage and infliximab double dosage were 4 (3-6), 4 (3-6), 8 (4-66), and 4 (3-11) patients, respectively. Conclusion: This study indicates equal efficacy of the three anti-tumour necrosis factor (TNF) therapies.