Carcinoma is treated in a patient by administration of Rhodamine-123 (Rh-123) orally or by intravenous injection of a treatment solution of Rh-123, ethyl alcohol, dextrose, and water in an amount sufficient to effect in vivo destruction of cancer cells. The treatment solution is made by mixing a stock solution of Rh-123 in a solution of 95% ethyl alcohol and 5% water (by volume) with a solution of 5% (by weight) dextrose in water. For prostate cancer, treatment is controlled by measuring the level of prostate specific antigen (PSA), or prostate specific acid phosphatase in the blood of the patient.