SummaryThe relationship between interleukin 6 (IL-6) levels and clinical parameters was studied in 25 patients with malignant pleural mesothelioma. The serum levels of IL-6, C-reactive protein, a,-acid glycoprotein and fibrinogen were significantly higher in mesothelioma than in lung adenocarcinoma with cytology-positive pleural effusion. Serum IL-6 levels correlated with the levels of the acute-phase proteins. We demonstrated a high incidence of thrombocytosis (48%) and a significant correlation between platelet count and the serum IL-6 level. The level of IL-6 in the pleural fluid of patients with mesothelioma was significantly higher than in the pleural fluid of patients with adenocarcinoma, and was about 60-1400 times higher than in the serum. However, even higher levels of IL-6 in the pleural fluid and of thrombocytosis were found in patients with tuberculous pleurisy. These results indicate that large amounts of IL-6 from the pleural fluid of patients with mesothelioma leak into the systemic circulation and induce clinical inflammatory reactions. These profiles are not specific to mesothelioma as similar profiles are found in patients with tuberculous pleurisy. However, the detection of a markedly increased level of IL-6 in pleural fluid argues against a diagnosis of adenocarcinoma.

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The combination of cisplatin and CPT-11 had definite activity against malignant pleural mesothelioma and was well tolerated. The intravenous administration of CPT-11 produced adequate distribution of CPT-11 and its active metabolite SN-38 into the pleural fluid and allowed a higher concentration of the more active SN-38 to make contact with mesothelioma cells in the thoracic cavity. These results warrant further clinical evaluation of this combination chemotherapy for the treatment of malignant pleural mesothelioma in a confirmatory Phase II trial.