Skin cancer is the most common form of cancer in the United States, and Florida has the second highest incidence of melanoma in the U.S., according to the Centers for Disease Control. For decades, melanoma, an aggressive and deadly form of skin cancer, has been challenging to treat. Chemotherapy and radiation proved ineffective. But recently, oncologists have been treating patients with melanoma with immunotherapy, an IV drug that stimulates the immune system to fight the disease. This newer approach is designed to kill cancer cells without damaging healthy ones. Not every patient, however, responds.