Obesity ‘should not influence’ choice between TNF, non-TNF therapies in RA
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In patients with rheumatoid arthritis initiating either TNF inhibitors or non-TNF inhibitor biologic therapies, severe obesity and low BMI each impeded treatment response, according to data published in Arthritis Care & Research.
The researchers additionally found the efficacy of TNF inhibitor and non-TNF inhibitor therapies to be statistically similar across the range of body mass.
“To date, there has been some question about whether certain therapies are less effective in patients with obesity,” Joshua F. Baker, MD, MSCE, of the University of Pennsylvania, in Philadelphia, told Healio. “In particular, there has been some concern that TNF inhibitors might be less effective.”
To compare TNF inhibitors to non-TNF inhibitor biologic therapies in patients with RA, as well as examine whether BMI impacts treatment response in each therapy, Baker and colleagues analyzed data from the CorEvitas database. Formerly known as Corrona, the CorEvitas registry is the largest independent database in North America collecting standardized outcome measures from rheumatologists and patients every 3 to 6 months, according to the researchers. For their study, Baker and colleagues obtained data 5,901 treatment initiations among 5,050 unique patients with RA.
Among the included patients, 2,721 — about 46% — were either obese or severely obese at the time of treatment initiation, with a mean group BMI of 30.5. The total study sample included 2,891 TNF-inhibitor initiators and 3,010 who received non-TNF-inhibitor biologics. The researchers analyzed three clinical outcomes based on the Clinical Disease Activity Index (CDAI) at 6 months from therapy initiation — low disease activity, change as large as the minimal clinically important difference (MCID), and absolute change.
The analysis included restricted cubic splines, to assess non-linear associations, as well as linear and logistic regression to evaluate associations with response, adjusting for confounders. In addition, the researchers examined interactions between BMI and class of therapy to determine whether comparative effectiveness of therapy varied by body mass.
According to the researchers, among all treatment initiators, those with severe obesity demonstrated lower odds of achieving LDA or MCID, and less improvement in CDAI. However, these associations were attenuated with adjustment. Meanwhile, low BMI was associated with reduced response rates in the adjusted models, including lower odds of LDA (OR = 0.32; 95% CI, 0.15-0.71).
In addition, an analysis stratified by treatment type found no differences between TNF-inhibitor and non-TNF-inhibitor therapies in clinical response rates across BMI categories (all P for interaction > .05). Estimates for non-TNF inhibitor biologics fit within the 95% confidence interval for TNF inhibitors.
“In our study, which included thousands of patients, obesity was indeed associated with lower response rates — underweight too,” Baker said. “However, there was no evidence to suggest one therapy was worse than another based on the patient's weight. This study provides some of the most convincing evidence to date that the presence of obesity should not influence a provider's choice of therapy for RA. While obesity appeared to lower rates of response, this was the same regardless of the class of treatment.”
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