Phase II Trial of Temozolomide in Patients with Relapsed Sensitive or Refractory Small Cell Lung Cancer, with Assessment of Methylguanine-DNA Methyltransferase as a Potential Biomarker

PURPOSE: This phase II study was conducted to assess the efficacy of temozolomide in patients with relapsed small cell lung cancer (SCLC). EXPERIMENTAL DESIGN: Patients with disease progression after one or two prior chemotherapy regimens received temozolomide at 75 mg/m(2)/d for 21 days of a 28-day cycle. The primary endpoint was the overall response rate ORR; complete response (CR) plus partial response (PR), which was evaluated separately in sensitive and refractory cohorts. In the available tissue, we assessed O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status by PCR and MGMT expression by immunohistochemistry. RESULTS: Sixty-four patients were accrued: 48 patients in the sensitive cohort and 16 in the refractory group. One CR and 10 PRs were noted in sensitive patients ORR, 23%; 95% confidence interval (CI), 12%-37%. Two PRs were seen in the refractory cohort (ORR, 13%; 95% CI, 2%-38%). As second- and third-line treatment, the ORR was 22% (95% CI, 9%-40%) and 19% (95% CI, 7%-36%), respectively. Among patients with target brain lesions, 38% had a CR or PR (95% CI, 14%-68%). Grade ≥3 thrombocytopenia and neutropenia were observed in nine patients (14%). A greater number of cases with methylated MGMT had a response compared to those with unmethylated MGMT (38% vs. 7%; P = 0.08). CONCLUSION: Temozolomide has activity in relapsed SCLC, particularly for brain metastases. Response to temozolomide may correlate with MGMT methylation in SCLC.