Comorbid Fibromyalgia Reduces Effectiveness of Biologics in Psoriatic Arthritis

Comorbid fibromyalgia, the female sex, and obesity may be the worst prognostic factors of clinical outcomes of biologics in patients with psoriatic arthritis (PsA), according to study results published in Rheumatology. 

Researchers investigated the effect of comorbid fibromyalgia and PsA on biologic treatment outcomes and determined the potential of fibromyalgia as a “predictor of an early clinical response.” They analyzed outcomes for patients with PsA starting treatment with a biologic drug or apremilast at a clinic at Bari University in Italy. Of the 238 patients seen between January 1, 2010 and June 30, 2017, 58 were diagnosed with fibromyalgia. All patients were biologic-naive prior to first biologic treatment initiation and demographics, disease features, and comorbidities (eg, anxiety/depression, hypertension, diabetes, liver disease, and anemia) were recorded at baseline.

The study’s primary end point was survival on the first biologic drug (adalimumab, etanercept, golimumab, infliximab, certolizumab, ustekinumab, secukinumab, or apremilast). The secondary end point was achievement of low disease activity or remission, and minimal disease activity was assessed at 3-, 6-, 12-, and 24-month follow-ups.

The majority of patients with PsA and fibromyalgia were women (74%; P =.0001). Significant differences in mean body mass index scores were observed in the comparison of patients with and without fibromyalgia (28.5 vs 26.3 kg/m², respectively; P =.006). Another area of reported significance was in clinical phenotype with the peripheral polyarticular subset being more prevalent in patients with PsA and fibromyalgia than in those without fibromyalgia (83% vs 40%; P =.0001). 

Patients with fibromyalgia and PsA experienced significantly lower biologic drug survival rates (50%; mean survival time [MST], 32 months; 95% CI, 25-38 months) than patients with PsA without fibromyalgia (74%; MST, 42 months; 95% CI, 38-45 months; P =.0001). Patients with PsA and fibromyalgia had significant reductions in disease activity at 3 and 6 months, but worsened at 12 months, and showed negligible percentages for disease remission. In patients with PsA without fibromyalgia, significant decreases in disease activity were seen at 6 and 12 months (6.8 and 6.3, respectively; P =.0001). 

Study limitations included the retrospective analysis, which may have introduced unknown biases, and that the cohort was not large enough to assess effectiveness of the different diverse drugs in patients with fibromyalgia and PsA. 

Researchers indicated that patients with PsA and fibromyalgia “were more frequently classified as belonging to the polyarticular subset.” They indicated that this finding “[raises] the question of whether [fibromyalgia]-related tender points may lead to the misclassification of patients [with PsA] with peripheral arthritis.” Finally, the researchers concluded, “gender, obesity, and fibromyalgia are the main determinants influencing the clinical outcomes of PsA in real-life settings.” However, they also noted that comorbidity in this population “is still an open and unanswered question that needs to be addressed in order to successfully treat patients [with PsA] in daily clinical practice.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures. 

Reference

Iannone F, Nivuori M, Fornaro M, Venerito V, Cacciapaglia F, Lopalco G. Comorbid fibromyalgia impairs the effectiveness of biologic drugs in patients with psoriatic arthritis [published online October 25, 2019]. Rheumatology. doi:10.1093/rheumatology/kez505