To the Editor.—
Recently, Oberg et al1 reported symptomatic relief of carcinoid syndrome and decreases in tumor-associated metabolic products in six of nine patients receiving 3×106 to 6×106 units/day of leukocyte interferon intramuscularly for three months. Interestingly, with regard to possible effects on tumor growth, they were unable to demonstrate any histological changes or decreases in tumor size.Human interferons include proteins derived from fibroblasts and immune cells as well as those derived from leukocytes. The various molecular species differ both in regard to polypeptide sequence and carbohydrate content. Both in vitro2 and in vivo3 studies indicate that these various types of interferons can demonstrate tumor cell specificity.
Report of a Case.—
We recently treated with fibroblast interferon a 51-year-old man with biopsy-proved carcinoid of the rectum with multiple liver metastases. He had no symptoms of the carcinoid syndrome, and a 24-hour urine collection was