medwireNews: Both underweight and obese people with rheumatoid arthritis (RA) are at increased risk for discontinuing tumor necrosis factor (TNF) inhibitor treatment earlier than their normal weight counterparts, real-world study findings indicate.
The effect was strongest among patients from obesity class III (BMI >40 kg/m2) but was not associated with reported levels of pain, as has been previously suggested, in any BMI category, note Sytske Anne Bergstra (Leiden University Medical Center, the Netherlands) and co-investigators.
The findings, published in RMD Open, are based on data for 5230 individuals with RA from the international METEOR registry.
Of these, 72% stopped treatment with their first TNF inhibitor (etanercept, adalimumab, infliximab, certolizumab pegol, or golimumab) during a maximum 13.5 years of follow-up.
Overall, the median treatment duration was 32.6 months for underweight participants (BMI<18.5 kg/m2; n=153), 34.9 months for those who fell into the normal weight (BMI 18.5–25 kg/m2; n=1897) and preobesity (BMI 25–30 kg/m2; n=1332) categories, 34.7 months for those in obesity class I (BMI 30–35 kg/m2; n=528), 29.7 months in obesity class II (BMI 35–40 kg/m2; n=142), and 21.1 months in obesity class III (n=64).
After adjustment for potential confounders, the researchers found that the risk for discontinuation was a significant 67% higher in people with class III obesity and 28% higher among those with class II obesity, relative to the normal weight participants.
In addition, people who were underweight had a significant 30% higher risk for discontinuation than those who were in the normal weight category.
Reported pain levels were not associated with a significant effect modification, “indicating that the association between BMI and drug survival was similar in patients reporting different levels of pain,” Bergstra et al remark.
“However, we did observe that the last measured DAS28 before stopping treatment was higher for patients in higher BMI categories,” they add.
Separate analyses for adalimumab, etanercept, and infliximab (numbers were too small for certolizumab and golimumab) showed that the effect was strongest for underweight patients on infliximab (hazard ratio [HR] for discontinuation=1.82) and obesity class III participants on etanercept (HR=1.79).
When the analyses were limited to the first year of follow-up, the researchers observed similar results, with the shortest TNF inhibitor survival among participants in the underweight and class III obesity categories, at HRs of 1.37 and 1.40, respectively.
The risk for discontinuation during the first year was particularly high among obesity class II and III individuals on etanercept (HR=1.64 and 2.23, respectively) and underweight people on adalimumab (HR=1.58).
Bergstra and co-authors say that “in clinical practice, differences in treatment survival may be expected for patients with different BMI levels on different TNF [inhibitors].”
“Moreover, underweight patients seem to be a neglected group in research that may require customised treatment,” they add.
And the team concludes: “Whether interventions to stimulate weight loss for instance could lead to a better treatment response in obese patients remains to be elucidated.”
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