How would a 19 year old male with relapsed all leukemia progress if he decides to stop treatment entirely? how long would he last?

ALL: Acute lymphoblastic leukemia is treatable on relapse however without treatment often is rapidly fatal. There are many excellent centers that treat all and adolescents and young adults. I would strongly urge him to seek a second opinion at one of those centers.

It's impossible....: To know. I've had patients who i thought would succumb to their disease quickly survive for over a year without treatment while other patients who appeared well and i thought would survive for a while died quickly. The leukemia is part of the picture, but risks for life threatening infection, acute and chronic end organ failure, etc. Further complicate the clinical picture.