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Experimental studies have showed that hepatocellular carcinoma (HCC) cells are susceptible to cytolysis of interleukin (IL)-2-activated lymphocytes. Moreover, our previous studies demonstrated that the pineal neurohormone melatonin (MLT) may enhance IL-2 efficacy. On this basis, a study was started with low-dose IL-2 (3 million U/day subcutaneously for 6 days/week for 4 weeks) plus MLT (50 mg/day orally every day given in the evening) as a first-line therapy of unresectable HCC. The study included 14 patients. Objective tumour regressions were obtained in 5/14 (36%) patients (one complete response, four partial responses), with a median duration of 7+ months. 6 patients had stable disease, while the other 3 progressed. Toxicity was low in all cases. This study shows that the neuroimmunotherapy with low-dose IL-2 plus MLT is a new well-tolerated and effective therapy of advanced HCC.

The advanced tumours of the digestive tract are generally less responsive to conventional chemotherapies. Moreover, preliminary results with IL-2 immunotherapy also seem to show a low efficacy. On the basis of our previous studies suggesting s synergistic action between IL-2 and some neurohormones, such as the pineal indole MLT, a clinical trial was performed to investigate the clinical efficacy and tolerability of an immunotherapy with IL-2 plus MLT in patients with advanced neoplasms of the digestive tract. The study included 35 patients (colorectal cancer: 14; gastric cancer: 8; hepatocarcinoma: 6; pancreas adenocarcinoma: 7). Distant organ metastases were present in 31/35 patients. MLT was given orally at a daily dose of 50 mg at 8.00 p.m., starting 7 days before IL-2, which was given subcutaneously at a dose of 3 million IU/day at 8.00 p.m. for 6 days/week for 4 weeks, corresponding to one cycle of immunotherapy. In nonprogressed patients, a second cycle was given after a 21-day rest period. A complete response was achieved in two patients (gastric cancer: 1; hepatocarcinoma: 1). Six other patients obtained a partial response: (gastric cancer: 2; hepatocarcinoma: 2; colon cancer: 1; pancreas cancer: 1). Therefore, the overall response rate was 8/35 (23%). Stable disease was obtained in 11/35 (31%) patients, whereas the remaining 16 patients (46%) progressed. The response rate was significantly higher in untreated patients than in those previously treated with chemotherapy. Toxicity was low in all patients, who received the treatment as a home therapy. This study shows that the immunotherapy with low-dose IL-2 plus the pineal hormone MLT is a new well tolerated and effective therapy of advanced tumours of the digestive tract, mainly in gastric cancer and hepatocarcinoma.