The difference between maintenance therapies and IRTs?
Background
There are two main treatment philosophies when it comes to treating MS with DMTs; maintenance-escalation vs. immune reconstitution therapies (IRTs).
What is an IRT?
By definition an IRT is given as a short course, i.e. as a one-off treatment in the case of HSCT or intermittently as in the case of alemtuzumab, cladribine or mitoxantrone. IRTs are not given continuously and additional courses of the therapy are only given if there is a recurrence of MS inflammatory activity. IRTs have the ability to induce long-term remission and, arguably, in some cases a potential cure. Cynics would argue that none of our treatments cure MS, but unless we define what constitutes a cure and look for it we won’t find it.
What is a "cure" for MS?
One attempt defines an MS cure as no evident disease activity (NEDA) 15 years after the administration of an IRT. I justify using 15 years as it is the most commonly accepted time-point for defining 'benign MS' and happens to be beyond average time to the onset of secondary progressive MS in natural history studies.
What is a maintenance therapy?
In comparison, a maintenance therapy by definition is given continuously without an interruption in dosing. Although maintenance therapies have the ability to induce long-term remission, i.e. NEDA, they cannot by definition result in a cure. With maintenance therapies the recurrence of, or ongoing, inflammatory activity, is an indication that there is a suboptimal response to treatment and typically results in a treatment switch. Ideally this switch should be to a more effective class of DMTs, hence the term escalation.
What would I recommend?
I can't choose for you. The debate between being treated with a maintenance therapy and an IRT is complex and depends on many factors. The table embedded in this slideshow below highlights key differentiators. The best way to understand the complexities around the choice between these two options is to review some of the case studies presented on this site. It is vital to understand the difference between continuous long term and short-term intermittent immunosuppression.
