Carcinoid Tumor Response to Fibroblast Interferon

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