7201 Background: Malignant pleural mesothelioma (MPM) is a rare and aggressive neoplasm of the lining of the lung. Only case reports are available for treatment and outcome of AbM. Pemetrexed (ALIMTA™) is a novel antifolate targeting key enzymes in purine and pyrimidine synthesis. Recently data from a randomized phase III trial have shown superior efficacy of pemetrexed/DDP vs DDP alone in MPM, however, no data of pemetrexed in AbM are available. METHODS In an open label trial, efficacy and safety data of pemetrexed (500 mg/m2) +/-DDP (75 mg/m2) or carboplatin (AUC 5) were studied to obtain data for AbM and MPM. A total of 49 mesothelioma pts with stage III/IV were observed between 12/02 and 11/03. Pts received pemetrexed based therapy including dexamethasone prophylaxis for skin rash on day -1 to+2 additionally. Folic acid 400 μg po daily, prior to and during study, and vitamin B 12 1000 μg i.m. q 9 wks in addition was administered to prevent adverse events. Study endpoints were response (RR), time to progression (TTP) and safety. RESULTS Four pts (1 AbM, 1 MPM, 2 MPM+AbM) were excluded due to renal impairment (n=1) or death prior to chemotherapy (n=3). 45 mesothelioma pts (34 m/11 f) were treated with pemetrexed. Staging revealed AbM in 11 pts, MPM in 30 pts, while 4 pts had malignant mesothelioma on both sites of the diaphragma. Initial combination was with DDP in all pts with AbM, while this was DDP in 23, and carboplatin in 11 of the remaining 34 pts. Pemetrexed was administered a median of 6 cycles (range 1-13). Major toxicities (WHO >°III/IV) were nausea and neutropenia (2/11). Up to 11/03 death has been reported due to PD in 19 out of 49 pts, including 5 of 11 pts with AbM. Treatment and response data are given in the table below. Data regarding TTP will be presented at the meeting. CONCLUSIONS Pemetrexed in combination with DDP is a well tolerable and active regimen for advanced peritoneal malignant mesothelioma. [Figure: see text] No significant financial relationships to disclose.