Fortunately Non-Hodgkin's Lymphoma tends toe be non fatal, unless left for a very long time [20 years or more]. The only downside to non fatal Cancers like Lymphoma is that they tend to come back [I speak from experience as I've had 3 bouts of Non Hodgkin's Lymphoma]

The Chemotherapy [and/or radiation] treatments will wreck him more than the Cancer will.