Phase I Trial of Cisplatin, Pemetrexed, and Imatinib Mesylate in Chemonaive Patients With Unresectable Malignant Pleural Mesothelioma

BackgroundWe conducted a phase I trial of cisplatin/pemetrexed/imatinib mesylate, an oral platelet-derived growth factor receptor (PDGFR) inhibitor, in chemonaive patients with malignant pleural mesothelioma (MPM).MethodsA standard 3 + 3 dose-escalating trial was used with the end points of maximum tolerated dose (MTD), response rate, survival, safety/toxicity, and tumor PDGFR levels.ResultsSeventeen patients with MPM were enrolled. The most common (any grade) side effects were nausea, fatigue, hypomagnesemia, and anemia. The MTD was established at dose level 3 (imatinib 600 mg) with a dose-limiting toxicity (DLT) of nausea and vomiting. The median progression-free survival (PFS) was 7.9 months and the median overall survival (OS) was 8.8 months. Patients with a sarcomatoid subtype had worse PFS (P = .01) and OS (P = .009), whereas they had a better Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-1 predicted for improved OS (P = .001) and PFS (P = .013). The 6 patients who completed all 6 treatment cycles had better OS (P = .006); the median PFS was 9.6 months and the OS was 22.4 months. In the translational studies, 14 patients had adequate tumor tissue that could be assessed for immunohistochemical (IHC) analysis and fluorescence in situ hybridization (FISH). Patients with higher than median p-PDGFRα IHC expression had a better OS (P = .013). When assessed as a continuous variable, higher p-PDGFRα in tumor cells correlated with an improved OS (P = .045). None of the other 4 IHC biomarkers were predictive or prognostic for survival. Twelve patients had successful PDGFRB FISH results, but none met the criteria of ≥ 4 copies of the PDGFRB gene; thus a correlation with clinical outcomes could not be done.ConclusionThe cisplatin/pemetrexed/imatinib mesylate combination had clinical benefit in some patients with MPM but was not well tolerated. Further investigation into alternative antiangiogenic agents, including PDGFRα inhibitors, is warranted.