I can't speak to for all states, but in South Carolina there are a number of programs for cancer screening of uninsured patients such as the
Best Chance Network and community programs for prostate screening for men. Once a cancer is diagnosed, if patients live in the central area of SC, they are usually referred to my oncology group where they are treated for free in exactly the same way they would be if they had insurance. Pharmaceutical companies replace the chemo drugs we use for free, and we have a charitable foundation that picks up ancillary costs for pain meds, nausea meds, transportation, etc. The physician's time, nurses salaries, IV tubing, lab tests, x-rays, radiation treatments, etc. are donated by my group.