Using a Steroid Mouthwash to Prevent Mouth Sores During Chemotherapy

The goal of this clinical trial is to learn if a steroid mouthwash (dexamethasone) can prevent mouth sores caused by chemotherapy in adults with cancer. The main questions it aims to answer are: Does using dexamethasone mouthwash before and during chemotherapy lower the chance of getting moderate to severe mouth sores? Can this approach reduce pain and improve comfort during chemotherapy? Researchers will compare patients using the mouthwash to a historical group of patients who received similar chemotherapy but did not use the mouthwash, to see if the mouthwash helps prevent mouth sores. Participants will: Use a steroid mouthwash (4 times daily) for up to 8 weeks during chemotherapy Complete a short weekly survey about mouth discomfort during infusion visits