Assume you’re life-lusted and are willing to abandon every moral you have just to live. Paying for cancer treatment is also worth prison time to you.
Also assume you’ve exhausted all ethical fundraising options, i.e. GoFundMe, loans, etc. and that insurance won’t cover treatment for whatever reason.
I don’t think stealing would be the hard part. Selling the goods would be. To steal large sum I guess I will drive a stolen car through a jewellery store’s window. I believe this had fairly high success rate with Romanian gangs doing this many times in France and getting away with it. To steel a car I would look for someone leaving it running while and getting out to for a moment. I think I would be able to find one in a couple of weeks. Than smash the widow, grab what I can and run. Risky but if I’m dying anyway it would be worth trying. Turning it into cash would be very difficult though.
You could always hawk it as new on Ebay.
Where I live police monitors those things. They will even check pawn shop inventory for jewellery reported as stolen and you have to show an ID to pawn anything. You would have to sell it to some random guys on the street which would be risky.
Sell it in another country or online.