medwireNews: Axial spondyloarthritis (axSpA) patients may be less likely to stop taking tumor necrosis factor (TNF) inhibitor treatment if they receive it in combination with a conventional synthetic (cs)DMARD, EuroSpA registry findings show.
The results, presented at the EULAR 2020 E-Congress, suggest that axSpA patients receiving TNF inhibitor monotherapy have a 12–13% higher risk for treatment discontinuation than patients taking TNF inhibitors in combination with csDMARDs.
A total of 22,196 axSpA patients who started taking a TNF inhibitor for the first time between 2006 and 2017 were identified from 13 European registries. Of these, 14,633 (66%) were taking TNF inhibitor monotherapy and 7563 (34%) a TNF inhibitor in combination with a csDMARD.
“The groups were largely similar apart from disease duration, which was slightly higher in the combination group, there were slightly higher rates of swollen joint counts, and the CRP [C-reactive protein level] was similarly somewhat higher in the combination group,” observed presenter Michael Nissen (University of Geneva, Switzerland).
The crude TNF inhibitor retention rate over 12 months was slightly higher among patients in the combination group, at 80% compared with 78% among patients in the monotherapy group, which Nissen noted was “highly significant, but the small difference may well not be clinically relevant.”
However, when they looked across the various countries, the researchers found that the difference was most notable in those where the TNF inhibitor retention rate is below average, such as Denmark, Finland, Iceland, Norway, Sweden, and Switzerland. For these countries, the average TNF inhibitor retention rate over a year was 77% for patients receiving TNF inhibitor therapy combined with a csDMARD versus 72% for patients receiving TNF inhibitor monotherapy.
In countries where the TNF inhibitor retention rate is above average, including the Czech Republic, Italy, Portugal, Romania, Slovenia, Spain, and Turkey, the rates of TNF inhibitor retention were only slightly different, at 87% for the combination group and 89% for the TNF inhibitor monotherapy group.
Nissen pointed out some significant differences between the countries in terms of treatment, including a higher use of infliximab in the csDMARD plus TNF inhibitor group versus the TNF inhibitor-only group in countries with below average TNF inhibitor retention rates. He said this was “somewhat in relation to the use of methotrexate,” which was also higher in the combination group in these countries, compared with countries with above average retention rates, where sulfasalazine was used more frequently.
Nissen concluded that the next steps are to further explore why there are “considerable differences” in the TNF inhibitor retention rates and the use of combination versus monotherapy across Europe, including whether it relates to the type of csDMARD or TNF inhibitor used, or indeed the gross domestic product per capita, which he pointed out is three times higher in countries were TNF inhibitor retention rates are below versus above average.
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