Recurrence with treatment questions

I was diagnosed with stage 3 bladder cancer back in 2015.Underwent 4 months of chemo then major surgery to remove bladder as well as prostate and surrounding lymph nodes then had a neo bladder constructed.All was fine and check ups ok until I began to have symptoms occur which ranged from constant back/torso pain as well as intermittent blood clots. This past Thursday had a bronchoscopy performed and was verified that cancer had returned in lymph nodes in both lungs and oncologist did classify it to be stage 4 at this time. Am now preparing under his advisement to begin mvac chemo with four treatments over the next several weeks then will test to see if any change and was discussed that if no effect then immunotherapy would be next step. I am not familiar with immunotherapy at all so am very curious to get any info/insight into this and am also very much wanting to look into any and all possibilities as far as alternative medicines/care including any input in regards to the medicinal marijuana debate as far as pros/cons involved. Any info/input I can get is greatly appreciated!