Sometimes it's difficult from telling the difference of thrush, which is one of a few candidal infections, from a bacteral or viral infection, and could be a number of things with a compromised immune system with cancer. Just taking a guess that it could be herpes simplex vurus, HSV, brought out by treatment, candidal leuckoplakia with raised, white, or speckled (mixed white, red) plaques, salivary gland dysfunction, speckled leukoplakia.

Good luck. Maybe they can do a throat culture. Good luck.