A 66-year-old man presents for evaluation of skin growths on his face. For several years he has had scaly, rough growths on his face, forehead, and scalp. He has had individual lesions frozen off by previous physicians, bud he keeps getting more and more. He has never been diagnosed with skin cancer. He has a long history of sun exposure and multiple sunburns, primarily as a consequence of working outdoors and playing golf. He takes an aspirin a day and pravastatin for high cholesterol. He has no other significant medical history. On examination of his you note multiple 4-7 mm lesions on the face and scalp that are flat, pink, and scaly. They feel rough on palpation. They are all in areas that would be sun exposed. He has several on the dorsal surface of his hands and forearm. You diagnose him as havening multiple actinic keratoses. Along with recommending skin protection from the sun, you prescribe topical 5-fluorouracil (5-FU)