Well,
when a patient has gone into remission,it usually means that the cancer has gone,died,or is at bay for the time being......it is a good sign that he will be ending treatment soon

.....it doesn't mean the cancer has fully gone away however.
Doctors in the Oncology field who have dealt with this type of cancer tend to estimate how long of treatment someone must go through in order to kill the cancer cells and they determine it by other cases and studies recorded to see if his case is similar or needs more time.