Treatment of malignant carcinoid tumors with human leukocyte interferon: long-term results.

Thirty-six patients with malignant carcinoid tumors were treated with human leukocyte interferon (IFN) im at doses of 3-6 megaunits/day. The origins of the primary tumors were as follows: mid-gut (29 patients); pulmonary (four); rectal (one); ovarian (one); and unknown (one). Nineteen of the 36 patients had previously been treated with cytotoxic agents, streptozocin plus 5-fluorouracil or doxorubicin, but showed progressive disease. With IFN objective tumor responses were seen in 17 of the 36 patients (47%): in 14 of the 29 patients with mid-gut carcinoids (48%) and in three of the four patients with lung carcinoids (75%). The median duration of response was 34 months. Stable disease was noted in 14 of 36 patients (39%), all presenting mid-gut carcinoids. The median duration of stable disease was 25 months. Progressive disease from the start of IFN therapy was seen in five patients (14%). All responders except one had a greater than 50% reduction of urinary 5-hydroxyindoleacetic acid or alpha-human chorionic gonadotropin, whereas four patients also had a significant reduction of tumor size on computerized tomographic scan or at laparotomy. Two patients achieved complete remission. Improvement of clinical manifestations of the carcinoid syndrome was seen in all patients with objective response. Adverse effects including influenza-like syndrome, reduction of blood cells, chemical signs of liver dysfunction, and disturbed lipid metabolism occurred but were reversible or could be circumvented by dose reduction. Autoimmune phenomena were also noted such as development of thyroid autoantibodies with thyroiditis, SLE syndrome with antinuclear factors, and parietal cell antibodies with pernicious anemia. IFN therapy seems to be very effective in controlling tumor-secreted substances and thus giving relief of clinical symptoms. It also arrests tumor growth for extended time periods (median, 2 years). The adverse effects are surmountable and less severe than with cytotoxic therapy.