ROME – Radiographic progression occurs at similar rates in the spines of ankylosing spondylitis patients treated over 2 years with either continuous or on-demand diclofenac, according to results from a randomized, prospective multicenter trial presented at the European Congress of Rheumatology.

In the ENRADAS (Effects of NSAIDs on Radiographic Damage in Ankylosing Spondylitis) trial, Dr. Joachim Sieper of Charite-Universitätsmedizin Berlin and his colleagues compared continuous treatment with at least 50% of the maximum 150-mg daily dose of the NSAID diclofenac and on-demand treatment with diclofenac. During the entire 2 years of the study, no patient received treatment with a tumor necrosis factor blocker or any other drug other than diclofenac.

Dr. Joachim Sieper Mitchel L. Zoler/Frontline Medical News

Dr. Joachim Sieper

The investigators measured radiographic spine progression using the modified Stoke Ankylosing Spondylitis Spinal Score(mSASSS). At baseline, patients randomized to continuous treatment who had complete radiographic follow-up had a mean mSASSS of 10.9, while those randomized to the on-demand arm had a mean mSASSS of 16.4. After 2 years on treatment, the average change in mSASSS from baseline was 1.28 for the 62 patients in the continuous-treatment group and 0.79 for the 60 patients in the on-demand group, a difference that was not statistically significant, Dr. Sieper said.

There also was no statistically significant between-group difference when the analysis focused on the subgroup of patients who were C-reactive protein positive at baseline, 55% and 58% of patients in the groups, respectively, who had their average mSASSS increase by 1.68, compared with 0.96. Similarly, when the analysis focused only on patients who had syndesmophytes at baseline, 53% and 62% of patients, respectively, the average increases in mSASSS were 2.11 and 0.95, a difference that was not statistically significant. Presence of C-reactive protein and syndesmophytes are both known risk factors for radiographic progression.

Patient characteristics were similar in the two groups. NSAID intake over the 2-year study period, measured using a 0-100 composite score based on treatment duration and NSAID doses and intervals, was a mean of 76 vs. 44 for the continuous and on-demand groups, respectively. At the study’s end, 77% of patients remained on diclofenac and had not switched to another NSAID.

Side effects were similar in both groups, with 19 serious adverse events in the continuous-treatment patients and 21 serious adverse events in the on-demand patients.

Previous studies have suggested that NSAIDs given continuously over 2 years reduce radiographic progression, compared with on-demand therapy, in ankylosing spondylitis patients. Similar effects were seen in a prospective cohort.

“In our study, continuous vs. on-demand treatment … did not prevent radiographic progression in [ankylosing spondylitis]. It is highly unlikely that the results would have been different with a higher number of patients, because we found a trend for less progression in the on-demand group,” Dr. Sieper said.

Additional study is needed to determine whether an NSAID other than diclofenac, specifically a COX-2 selective drug, would have a different effect on radiographic progression, he said.

Dr. Sieper reported receiving honorarium for consultancies, speaker’s bureaus, or grants from AbbVie, Janssen, Merck, Lily, Novartis, Pfizer, and UCB.