Here's one more benefit of exercise: 

Mice who spent their free time on a running wheel were better able to shrink tumors (a 50 percent reduction in tumor size) compared to their less active counterparts. Researchers found that the surge of adrenaline that comes with a high-intensity workout helped to move cancer-killing immune (NK) cells toward lung, liver, or skin tumors implanted into the mice.

Reddit comment is that the authors note that exercise:

• Protects against certain cancers and protects against disease recurrence cite 1/cite 2

• Improves patient-reported outcomes cite

• May directly suppress tumor growth cite

Source and more:

https://reddit.com/r/science/comments/46872s/mice_who_spent_their_free_time_on_a_running_wheel/