Right, same concept to break up kidney stones but for tumors. It was mostly theoretical/concept phase when I was involved but that was several years ago.
Ultrasound (well, high frequency sound) is a treatment for some forms of prostate cancer, I believe. The idea is the tumor cells are more fragile and can be disrupted before the surrounding healthy tissue is damaged beyond repair. Not really that different than x-ray treatments or some forms of chemo, really, the goal is to kill the tumor faster than it kills the normal stuff around it.
www.mayoclinic.org
The "holy grail" for cancer treatments are therapies that ONLY target tumor cells, nothing else, and can kill EVERY tumor cell while leaving the rest of the body intact. Very, very, few treatments offer this hope though, even the highly specific monoclonal antibody, CAR-T, or gene therapies always have some off target effect, possible tumor resistance, or residual disease possibility, though certainly some folks can achieve 100% remission for the rest of their natural lives. Given the multitude of ways "cancer" presents, it's just the way it is that each cancer really needs it's own specific therapy, there really is no "all cancer cure-all", it would be like trying to develop a protective suit that could "prevent all trauma".