Sometimes, yes. It depends on the type of cancer and the type of stem cell. Bone marrow transplants to treat leukaemia are a type of stem cell treatment. Chemo- and radiation therapy are used to kill the faulty blood cells in the patient, then new healthy ones are put back. Different types of blood cell can be made from the cells put back, so they do act as a type of stem cell.
There are certainly people working on other ideas about using different types of stem cells to treat different cancers, but I don’t know of any others actually in use yet.