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A multicenter, randomized phase III maintenance study of thalidomide (arm A) versus observation (arm B) in patients with malignant pleural mesothelioma (MPM) after induction chemotherapy.

7006 Background: Standard chemotherapy treatment does not lead to long-term survival; new treatment approaches are required. MPM is known for its high vessel count and levels of vascular growth factors. Suppression of the neo-vasculature by adding thalidomide in the maintenance setting might lead to improved progression free survival (PFS). We here report the final results of PFS, overall survival (OS) and toxicity.


METHODS
Patients with pemetrexed (500 mg/m2) and carboplatin (AUC 5) or cisplatin (75mg/m2)(q3) for ≥ 4 courses and no signs of progression were eligible. After obtaining informed consent patients were randomized to receive thalidomide 200 mg/day orally (A) or no treatment (B). CT scanning of the thorax and physical examination was performed every 2 months or earlier. PFS and OS were calculated from start of randomization. A number of 190 events were required to show an improvement of 50% in PFS.


RESULTS
From 05/2004 until 12/2009 222 patients from 8 Dutch and 4 Australian centers were included (111 in each arm). Median age: 64 yrs (range 41-82); 86% epithelial type; 215 WHO 0-1 and 6 WHO 2.


TOXICITY
Data of 216 (108 arm A; 108 arm B) patients showed few grade III-IV toxicities. Low platelet count was observed in 6 patients in arm A and 11 in arm B (p=0.31). Leukopenia in 2 patients in arm A and 3 in arm B. In arm A, 2 patients experienced constipation and 2 neurosensory problems. Cardiovascular events were seen in 2 cases arm A and 3 in arm B, none being considered treatment related. Based on the physician reported outcome there were 207 progressions observed, with median PFS of 16 weeks in arm A compared to 15 weeks in arm B (p=0.83) HR 1.0 CI 0.8-1.4. Median OS was 11 months in arm A and 13 months in arm B (p=0.09) HR 0.78 CI 0.57-1.1.


CONCLUSIONS
This is the largest maintenance study in patients with MPM reported so far. There is minimal toxicity associated with the use of thalidomide, however there is also no evidence of benefit in PFS or OS.