There is early research testing Ivermectin (among hundreds of other things) in-vitro against prostate cancer cells, but that's a very long way from knowing if it will eventually work on humans, much less determining *which* cancer situations it will make better or worse, or what the optimal treatment would be.

I wouldn't use it off-label to treat prostate cancer in 2025 unless you want to risk your health and life as a human lab rat in an uncontrolled experiment, but maybe 5–10 years from now they'll know more.