Imatinib For Small Cell Lung Cancer, Aiming For A Target In Vivo

Purpose: To evaluate the clinical efficacy of Imatinib Mesylate in untreated or sensitive relapsed small cell lung carcinoma patients. Secondary endpoints included assessment of the safety and tolerance of Imatinib, and an analysis of KIT expression in tumor samples. Patients and Methods: Patients with previously untreated small cell lung cancer (SCLC) or with a sensitive relapse (one prior regimen with a sustained response for over 60 days) were eligible. Imatinib was delivered at 600 mg on a daily basis. Response was evaluated at 6 weeks using SWOG criteria. Results: As planned in the study design, a total of 19 patients were included in the trial (9 chemonaive patients with extensive disease and 10 sensitive relapse SCLC patients). No objective responses were observed with most previously untreated patients staying on study for less than 30 days. The median time to progression was 1 and 1.2 month in the untreated and sensitive relapse groups, respectively. Only 4 out of 19 tumor samples (21%) stained for KIT by means of immunohistochemistry. Conclusions: No evidence of antitumor activity was observed in this small phase II trial including 19 SCLC patients treated with Imatinib Mesylate. KIT positivity in tumor samples appeared to be far less common than anticipated (21 vs. 70%). Future trials should include a screening procedure to evaluate KIT expression in SCLC samples. A better evaluation of KIT contribution to SCLC tumor progression needs to be achieved.