Predictors of response to etanercept-methotrexate treatment: a post hoc logistic regression analysis of a randomized, open-label study in Latin American patients with rheumatoid arthritis.

Background: Determining potential predictors of clinical response would allow a more personalized rheumatoid arthritis (RA) treatment approach in heterogeneous populations such as Latin American (LA) patients.

Methods: Post hoc analysis to identify baseline characteristics predictive of clinical remission in response to treatment with etanercept (ETN) plus methotrexate (MTX) in LA patients with moderate to severe MTX-resistant RA. We report data from the group of patients who received ETN 50 mg/week plus MTX (ETN + MTX, n = 281) in a clinical trial consisting of an initial 24-week open-label phase, followed by a 104-week extension. Remission was defined as 28-joint Disease Activity Score with erythrocyte sedimentation rate (DAS28-ESR) score < 2.6. Cutoff values to dichotomize baseline variables maximizing the detection of remission were obtained from Receiver Operator Curve analyses. Baseline dichotomized and categorical variables were analyzed altogether in a stepwise logistic regression model. Odds of attaining response at Weeks 24 and 128 were estimated for each significant predictor.

Results: At Week 24 and Week 128, 27% (66/241) and 42% (91/219) of patients in the ETN + MTX group achieved remission. On average, patients achieving remission were younger and had lower baseline ESR, lower Physician Global Assessment (PGA) scores, lower total Health Assessment Questionnaire (HAQ) scores, and lower visual analog scale (VAS) Pain scores compared with patients who did not achieve remission. The best subset of baseline variables predicting Week 24 remission in the stepwise regression model were age ≤ 49 years (odds ratio [OR] 2.93), body mass index (BMI) > 28.5 kg/m (OR 3.24), disease duration > 3.7 years (OR 2.22), ESR ≤ 42 mm/h (OR 2.72), PGA ≤ 6 (OR 3.21), tender joint count ≤ 14 (OR 2.25), and total HAQ score ≤ 1.6 (OR 2.86). At Week 128, age ≤ 42 years (OR 2.21), SF-36 Mental Health Scale score > 39.6 (OR 2.16), White race (OR 4.07), > 18 swollen joints (OR 2.11), and VAS Pain ≤ 41 (OR 6.05) at baseline were the best subset of significant predictors of remission.

Conclusions: In LA patients with RA, younger age, higher BMI, longer disease duration, higher SF-36 Mental Health Scale score, higher swollen joint count, and overall lower disease activity predicted clinical response to ETN + MTX therapy.

Trial Registration: ClinicalTrials.gov Identifier: NCT00848354.