Many people considering treatment will find it confusing that there are in fact two different types of HSCT available. Learning what differentiates myleoablative from  non-myleoablative HSCT is important in deciding where to be treated and which type is best suited for your specific needs .  On the whole most facilities offering this treatment will opt for one or the other. In more simple terms when considering MYLEOABLATIVE VERSUS NON-MYELOABLATIVE it is important to understand that both forms are  equal in respect of the fact that they both ablate (destroy) the lymphocytes in the body that are self intolerant, and are ultimately responsible for the underlying nerve damage/ destruction. These lymphocytes are the white blood cells that would normally be attentive to destroying bacteria and other harmful substances that make it into our systems, that by becoming rogue are intent on attacking the myelin sheath that surrounds our nerves. Either type of HSCT is designed to get rid of these errant blood cells and replace them with ‘Naive’ ones that are behaving correctly!


Myeloablative HSCT is the more stringent type of treatment. This is designed to almost completely wipe out  both the body’s (autoreactive) lymphocytes that are the cause of MS, as well as the bone marrow. This type of HSCT most commonly incorporates a BEAM (Carmustine, Cytarabine, Etoposide, Melphalan) chemotherapy protocol which is administered over a period of six days often with the addition of ATG for a couple of days as supplementary rather than essential  lymphoablation. This type of HSCT is considered to be the most reliable, as it destroys the lympocytes more completely and ultimately removes the chance of any of the ‘baddies” surviving!


The  Non-myleoablative protocol, varies according to the doctor performing it but on the whole it is a less harsh procedure where the  lymphocyte population is not entirely eliminated but instead “diminished” to a threshold level below which autoimmune-mediated damage occurs. The bone marrow is not completely wiped out,  which makes the treatment less dangerous and allows the patient to recover faster.  This  “gentler” chemotherapy coupled with a  lower mortality rate has the trade off that, compared with the myeloablative protocol, there remains a proportion of patients  (20-25%) that fail to succeed in destroying all of the  lymphocytes needed to halt the disease. This can be dealt with post-transplantation  by using “top-ups” of cyclophosphamide infusions (more chemo) retreatments –  to coax  a treated MS patient that has not responded favourably  back into remission. 
It is the general consensus of opinion that if you have a progressive form of MS (PPMS or SPMS) Myleoablative HSCT is the most effective treatment. The general trend however with treatment is a movement towards non-myleoablative as a more favoured treatment around the world. There are currently no places that offer Myleoablative HSCT that will actually treat progressive cases of MS but as more results become available it is exciting to see marvelously successful results using Non-myleoablative HSCT for PPMS and other progressive cases.  The protocol is being continuously tweaked, and the attractive prospect of a less harsh experience coupled with faster treatment and faster recovery times continue to  popularize this option.