Long term outcome for onabotulinumtoxinA (Botox) therapy in chronic migraine: A 2-year prospective follow-up audit of patients attending the Hull (UK) migraine clinic

Objective: The objective of this prospective audit was to determine the long term outcome of patients diagnosed with chronic migraine who were treated with onabotulinumtoxinA for the prevention of chronic migraine. Background: While long term and real-world studies have confirmed the safety and efficacy of onabotulinumtoxinA in CM, there remains limited information from large patient numbers on the number of cycles and duration of onabotulinumtoxinA needed to successfully convert chronic migraine to episodic migraine, development of resistance to treatment and sustainability of response after stopping treatment. Methods: A total of 655 adult patients diagnosed with chronic migraine who received onabotulinumtoxinA at the Hull Migraine Clinic were followed up prospectively for a minimum of 2 years. OnabotulinumtoxinA was delivered as per the PREEMPT study protocol and patients were asked to keep a headache diary for at least 30 days prior to and continuously after receiving onabotulinumtoxinA. The primary outcome assessed in this prospective real-world audit was either the number of patients who achieved a ≥50% reduction in headache days or migraine days or an increment in crystal clear days twice that of baseline in a 30-day period. Patients were also assessed for analgesic medication overuse. Results: Treatment data were available for 655 patients who commenced treatment between July 2010 and October 2016 and followed for at least 2 years (24–70 months), with the last follow-up taking place in September 2018. Of the 655 patients, 380 patients responded to treatment after two cycles and went on to receive the third cycle. Of these, 152 patients were still on active treatment at 2 years. A further 61 patients had relapsed and were on treatment at 2 years. Of the 228 patients who stopped treatment, 112 were successfully converted to episodic migraine and showed a sustained response, 28 reverted to chronic migraine after the initial response despite continuing treatment (developed resistance), 14 were lost to follow up and 61 patients after achieving remission relapsed after a mean of 9 months (range 4–24 months) and recommenced treatment with onabotulinumtoxinA. Conclusion: After a minimum of 2 years, 29.4% of patients with chronic migraine who initially responded to treatment were successfully converted to episodic migraine and maintained a sustained response. Forty percent of the initial cohort of responders continued therapy with onabotulinumtoxinA to manage their chronic migraine.