How To Get Cancer Treatment Without Health Insurance (growingfamilybenefits.com)
It is complicated, and specialists themselves are at liberty to get involved or not in many situations. My sister was in the middle of a bad divorce when she was diagnosed with a rare cancer. She had no insurance and no money. The hospital staff themselves assisted her to get emergency coverage using state programs and Medicaid. In the end (which was far too soon) her estate was left with bills that exceeded her assets anyway. It was shocking to me and family that none of the cancer specialists were willing to offer experimental treatments or even engage in studies. We strongly suspect it is due to the minimal nature of her coverage and the certainty of her inability to pay out of pocket for anything declined by Medicaid.
In short things have much improved from the days not long ago when you simply would be turned away, but the system is clumsy and complicated. Knowing exactly who to ask for help and filling out the paperwork right the first time are essential.
Interestingly, years ago when we returned to Miami from a self-funded missionary stint, I was not well (typhoid) and had concerns about some spots that looked suspiciously like skin cancer. I was broke and had no insurance of course. I went to the free clinic and was turned down because I was not an undocumented alien. It's complicated. The clinic was funded privately, and staff were volunteers, with immigrants in focus. I was told to apply for aid in my home state. Fortunately, I had a nurse friend who got me the help I needed.