Mitoxantrone in relapsing-remitting and rapidly progressive multiple sclerosis: Ten-year clinical outcomes post-treatment with mitoxantrone

Background: Mitoxantrone (MTX) has been used as an effective disease modifying treatment (DMT) in multiple sclerosis (MS). Evidence from studies demonstrates benefits of reduced relapse rates, MRI disease activity and disability progression in patients treated with MTX. While effective, MTX use has been limited due to potential adverse effects (AE) ranging from mild to potentially life-threatening AEs such as cardiotoxicity, bone marrow suppression and hematological malignancies. In this study we aimed to review the long-term clinical efficacy, tolerability, and AE profile of treatment with MTX in patients both with relapsing-remitting and rapidly progressive MS over a 10-year follow-up period. Methods: We collected prospective data of 70 patients with relapsing-remitting and rapidly progressive MS treated with MTX and followed-up over a 10-year period. Expanded disability status scale (EDSS) scores and annualized relapse rates (ARR) were assessed 1 year prior to MTX treatment, and at different time points (1, 2, 3, 5 and 10 years) during follow-up. We recorded the time to first relapse and 0.5-point EDSS increase to assess efficacy. We also obtained frequency data on AEs and patients withdrawn from treatment. Results: 70 patients were started on treatment with MTX with 53 patients (34 relapsing-remitting MS, 19 progressive disease) completing the course. Mean EDSS progressed from 5.5 to 6.5 in the relapsing-remitting group and 6.7 to 9.0 in the progressive group over the study period. ARR in the RRMS group reduced at all time points from 2.2 prior to MTX to 0.3 by year 10. We reported 3 significant AEs, one chicken pox and subsequent acute promyelocytic leukemia, one left ventricular systolic dysfunction, one pancytopenia. The commonest AE reported was nausea/vomiting in 28 (40%) patients. Seventeen patients (5 relapsing-remitting, 12 progressive disease) stopped treatment. In fifteen (87%) of these this was due to lack of efficacy. In the remaining 2 patients, MTX was stopped due to one patient developing chicken pox and the other developing first-degree heart block. Conclusion: Our study demonstrated that MTX is an effective disease modifying treatment for relapsing-remitting MS with a well-established risk profile. While MTX is now used less frequently, many MS and neurology services continue to follow-up patients who have been treated with MTX previously. Therefore, understanding the longterm effects risks and benefits remains relevant in this patient group. MTX is also a low-cost treatment in comparison to other high efficacy MS disease-modifying treatments and this may be beneficial in low resource settings.