Chemotherapy vs transplant as treatment for relapsed ALL
Treatment for relapsed ALL is either chemotherapy/radiation or bone marrow transplant. Low-risk relapsed ALL can be treated with chemotherapy alone, while for high-risk ALL, a bone marrow transplant is the treatment of choice. For patients who fall somewhere between low- and high-risk, the recommended treatment can be either chemotherapy or transplant, and a family might have to decide which route to take. The purpose of this section is to point out some of the pros and cons of each treatment to help parents make a decision.
As discussed in the section on relapse questions COG, BFM, and St Judes have slightly different definitions of standard/intermediate/high risk relapsed ALL. Depending on which institution you consult, your child might fall into a different risk classification. A classification that would track to a bone marrow transplant at one institution might track to chemotherapy only at another institution. Combined BM/EM relapses that occur soon after treatment ends are most likely to fall in the "grey area" of recommended transplant.
What does bone marrow transplant mean?
A transplant basically destroys the bone marrow in an attempt to kill all of the leukemia cells. The dosages of chemotherapy and radiation used in conditioning for transplant would literally kill the patient if the patient was not rescued by the donor's bone marrow. In addition, the donor cells often stimulate a "graft vs leukemia" effect so that the donor cells see the leukemia cells as foreign invaders and attack and kill them.
What about chemotherapy?
If the patient is not to undergo a transplant, the dosage of chemotherapy is not lethal. The treatment usually lasts about two years.
Transplant means a higher cure rate and a shorter treatment time. But: the chemotherapy/radiation treatment incurs a lot more toxicity, more treatment-related mortality, increased possibility of long term effects (for instance, chronic GVHD, sterility, growth inteference, late neurocognitive effects).
Chemotherapy or chemotherapy/radiation (without transplant) means a slightly lower cure rate and two years treatment time. The treatment is not so toxic, it is less likely to cause treatment-related mortality, and causes fewer late effects. But: if your child relapses again, transplant is a must, third remission chances are lowered considerably and your child has to go through everything above anyway with possibly more toxicity involved.
When will the transplant occur (how soon after diagnosis of relapse)?
For early isolated marrow relapses, the goal is to get solid remission, then transplant as quickly as possible because of the fear that the leukemia may come back. For later relapses, most protocols provide an additional month or so after remission before transplant. (Most kids will get into remission by the end of induction on relapse protocols.)
Another consideration: how the cure rate is affected by different types of transplant
The statement in the "Some facts" section that transplants give a slightly higher cure rate must be qualified. Some types of transplant give a higher cure rate than others. The type of transplant (in other words, how well the donor's antigens match your child's antigens, and whether the donor is a sibling, unrelated, or cord blood) that your child will have depends on the availability of a suitable donor, so you do not necessarily have a choice in the type of transplant that can be given.
Fully antigen matched sibling transplant (6/6)
Second best (about 5-15% lower)
One antigen mismatched sibling transplant
Fully matched antigen unrelated donor transplant
One or two antigen mismatched cord blood transplant
Third best (about 5-15% lower than second best)
- Two antigen mismatched sibling transplant: (5-15% lower than the above)
- One antigen mismatched unrelated donor transplant: (5-15% lower than the above)
Cord blood transplants are relatively new and exactly where they fit into this scheme are not known.