Early response to COX-2 inhibitors as a predictor of overall response in osteoarthritis: pooled results from two identical trials comparing etoricoxib, celecoxib and placebo

Objective. We evaluated whether early response to NSAIDs predicted later response, and when this was established. Methods. We evaluated pooled data from two identical 26-week, double-blind, randomized trials comparing once-daily etoricoxib 30 mg (n=475), celecoxib 200 mg (n=488) and placebo (n=244) in patients with knee or hip OA. The present analysis was limited to the 12-week placebo-controlled period. Patient-level OMERACT-OARSI response was determined at 2, 4, 8 and 12 weeks. The proportion of patients who maintained response status between these times was determined from binomial distribution using the exact method. Results. After 12 weeks of treatment, there were significantly more responders in the etoricoxib (59.8%) and celecoxib (57%) groups compared with placebo (34%; P<0.001 for etoricoxib or celecoxib vs placebo). About 77.2% of the patients receiving etoricoxib, 75.4% celecoxib and 58% placebo (P=0.001 vs etoricoxib; P=0.003 vs celecoxib) who were responders at 2 weeks were also responders at 12 weeks. When comparing response agreement (responder or non-responder) at 2 weeks and 12 weeks, 74.3% of the patients receiving etoricoxib, 73.2% celecoxib and 71.3% placebo had the same response status (,c-coefficient 0.459, 0.449 and 0.357, respectively). There were small incremental increases in agreement between Weeks 4 and 8 and 12 weeks. Logistic regression showed that agreement was not affected by index joint (P=0.965). Conclusions. The overwhelming majority of the patients who responded to treatment by 2 weeks remained responders at 12 weeks, with response status largely established within 2 weeks of treatment initiation. Early identification of NSAID response or non-response may allow clinicians to better and more rapidly adjust symptomatic OA management.