Objective: Data from CD PROBE (Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy), an observational, multicenter, prospective clinical registry, were analyzed to try to identify characteristics and treatment practices that might be predictive of response to onabotulinumtoxinA (onabotA) in patients with CD.

Background: CD PROBE was designed to capture real-world data on the effectiveness and safety of onabotA for treatment of CD.

Methods: In this exploratory analysis, a response was defined as a ≥30% and/or ≥10 point reduction in TWSTRS total score from baseline to final visit. Relationships between onabotA doses, treatment interval, and response were analyzed by linear regression. Disease and treatment characteristics as predictors of response were evaluated using logistic regression.

Results: There were no clinically significant differences in onabotA doses (mean, median, or cumulative), or in treatment time intervals between responders (n=254) and non-responders (n=187). Doses at first treatment were initially greater for responders (188 U) than non-responders (168 U; P=.013), but the difference was only 20 U. By treatment 3, doses were the same in both groups (due to greater dose escalation in non-responders). Logistic regression analysis indicated that those patients with higher TWSTRS total score at baseline had a higher probability of response (P=.007) and those with anterocollis had a significantly lower probability of response (P=.028).

Conclusions: CD patients with higher baseline TWSTRS total score were more likely to respond whereas patients with anterocollis were less likely to respond to treatment with onabotA, consistent with clinical experience. Otherwise, there were no clinically significant differences in onabotA dose or treatment time intervals between treatment responders and non-responders. A major limitation is that the study was not designed to assess predictors. Controlled studies, rather than observational studies, may be necessary to determine treatment response. As there are no reliable predictors of response, treatment of CD with botulinum toxin must be individualized and tailored to the specific needs of each patient.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/predictors-of-onabotulinumtoxina-treatment-response-in-patients-with-cervical-dystonia/