I have ALL and I was just wondering at what time it would be most likely to relapse. Am I getting less and less likely to relapse the further I go into treatment, or is it that you're more likely to relapse after all of the treatment is done?

This is a question that many adolescent and young adults with acute lymphoblastic leukemia (ALL) ask.  The short answer to your question is: it depends.  Keep reading for the long answer!

In the past thirty years, the cure rates for ALL have improved from 20% to more than 80%.  Much of this progress can be attributed to enrolling higher risk patients on clinical trials with more intensive therapy and understanding specific risk factors for relapse.  What oncologists have learned is that one of the most accurate predictors of risk for relapse is how well your leukemia responds during the first month of treatment (called induction therapy).  Previously, this was measured by looking at bone marrow under the microscope to see if all of the leukemic cells had gone away during induction.  Now we use a new technique to examine the bone marrow during the first month for leftover leukemic cells called Minimal Residual Disease (MRD).  MRD is 100 times more sensitive than just looking under the microscope.  The sooner a patient's blast cells disappear during induction, the less likely it is that the patient will relapse.  However, it's important to remember this is not 100% and people are still cured even if it takes a long time for their blasts to disappear.  

We also know that a number of other factors may contribute to the risk of relapse in ALL patients.  These risk factors include certain genetic profiles of leukemic cells, being male, being older than 10 years old, having a high white count at presentation, or the presence of disease in the central nervous system.  But again, none of these risks are 100% predictive of relapse.

All of these risk factors are used to determine which risk group a new patient might fall into: low risk, standard risk, high risk, or very high risk.  The low risk group only has about 10-15% chance of relapse, but the very high risk group may have as high as 70% chance.  Relapse can occur anytime after remission has been achieved.  Usually – but not always - the higher risk patients will be the ones who relapse on therapy and the lower risk patients will relapse off therapy.  The longer a patient remains off therapy, usually the less likely he or she will relapse, but we continue to monitor blood counts very closely for the first couple of years because the risk doesn't go away completely.  After five years, the risk of relapse is quite low and we begin to refer to patients as being "cured."  Hopefully, with all of the new therapies and research, this is a category more and more patients will soon reach.