CANCÚN, MEXICO – Most ankylosing spondylitis patients who have elevated disease activity and inflammatory back pain that is not controlled with conventional therapy have been shown to respond to anti–tumor necrosis factor therapy, according to findings from a recent study.
Importantly, "disease activity will most likely not result in improvement," Dr. Nathan Vastesaeger reported at the annual meeting of the Canadian Rheumatology Association. As such, "the treating physician should consider a defined trial period with a TNF inhibitor if disease activity is not controlled with conventional therapy," he said.
Specifically, patient age, peripheral enthesitis measure, C-reactive protein (CRP) level, functionality, and human leukocyte antigen B27 (HLA-B27) genotype are also associated with the likelihood that a patient with ankylosing spondylitis (AS) will respond to anti-TNF treatment, reported Dr. Vastesaeger.
The findings are based on analysis of data, separately and combined, from two randomized controlled trials to model the probability of achieving response or remission after initiating anti-TNF therapy or continuing conventional therapy with NSAIDs, disease-modifying anti-rheumatic drugs (DMARDs), or corticosteroids for AS, said Dr. Vastesaeger of Schering-Plough.
The two studies included in the analysis were the ASSERT (Ankylosing Spondylitis Study for the Evaluation of Recombinant Infliximab Therapy) trial and the GO-RAISE (Golimumab – A Randomized Study in Ankylosing Spondylitis Subjects of a Novel Anti-TNF mAB Injection Given Every Four Weeks) trial.
The two studies combined comprised 479 AS patients treated with anti-TNF drugs and 156 AS patients treated with placebo and continued conventional therapy. All of the patients included in the analysis had Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores of at least 4 and spinal pain assessment scores of at least 4, Dr. Vastesaeger reported.
The prediction model incorporated patient age, enthesitis score, CRP level, Bath AS Functional Index (BASFI) score, and HLA-B27 genotype. The mean age of the patients included in the analysis was 39.5 years, and the mean BASFI, CRP, and enthesitis measures were 5.4, 2.1, and 2.4, respectively.
For the ASSERT, GO-RAISE, and combined data, the area under the ROC curve for 50% improvement in BASDAI score (BASDAI50) at 12 weeks was 82%, 75%, and 77%, respectively, and for Assessment in AS (ASAS) partial remission at 24 weeks was 80%, 77%, and 78%, according to Dr. Vastesaeger. When the data were categorized by age (40 years or younger vs. older than 40 years), enthesitis score (0 vs. greater than 0), CRP level (0.6 mg/dL or less, greater than 0.6-2 mg/dL, and greater than 2 mg/dL), and BASFI score (4.5 or less, greater than 4.5-6.5, and greater than 6.5), "the area under the curve of the combined data set prediction model was 80% for [BASDAI50] response and 77% for [ASAS] partial remission," Dr. Vastesaeger reported. "This suggests a good prediction model according to the academic point system."
In a matrix model designed to represent increasing proportion of BASDAI50 response and ASAS partial remission with respect to baseline characteristics, "only 2% of patients who did not have BASDAI50 response at week 12 had ASAS partial remission at week 24," said Dr. Vastesaeger.
The development of the matrix model was reported by Dr. Vastesaeger and his colleagues online March 14 in Annals of the Rheumatic Diseases (Ann. Rheum. Dis. 2011 March 14 [doi:10.1136/ard.2010.147744]).
On the basis of the model, the investigators determined that patients younger than 40 years and those without enthesitis, in particular, demonstrated the highest likelihood of responding to TNF inhibition, and that these variables, along with CRP, functionality, and HLA-B27 status, are useful in the assessment of probable treatment response. The model, as an adjunct to expert opinion, "may help clinicians choose more appropriate therapies for patients in daily practice and may also help improve patient selection and protocol design for clinical studies," Dr. Vastesaeger concluded.
Dr. Vastesaeger is an employee of Schering-Plough. He reported having no conflicts of interest with respect to this presentation.