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

This phase II study was conducted to assess the efficacy of temozolomide in patients with relapsed small cell lung cancer (SCLC). 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. 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). Temozolomide has activity in relapsed SCLC, particularly for brain metastases. Response to temozolomide may correlate with MGMT methylation in SCLC.