5-day dosing schedule of temozolomide in relapsed sensitive or refractory small cell lung cancer (SCLC) and methyl-guanine-DNA methyltransferase (MGMT) analysis in a phase II trial.

7052 Background: MGMT promoter methylation and loss of MGMT activity are associated with improved sensitivity to alkylating agents. We recently reported that the oral alkylating agent temozolomide is active in 2nd- and 3rd-line treatment of relapsed SCLC at 75mg/m2/day for 21 out of 28 days (Pietanza et al, Clin Can Res 2012). Here we evaluate the 5-day dosing schedule of temozolomide in a second cohort of patients and analyze MGMT activity in both cohorts of patients on the same study. Methods: Patients with disease progression after 1 or 2 prior chemotherapy regimens received temozolomide at 200mg/m2/day for 5 out of 28 days (n=25). Those with sensitive (S-SCLC, n=16) and refractory (R-SCLC, n=9) disease were enrolled to assess safety. Available tumor tissue from patients treated according to either schedule was assessed for MGMT promoter methylation status by PCR and MGMT expression by immunohistochemistry (IHC). Results: An overall response rate of 12% was noted (3 partial responses: 1 S-SCLC, 2 R-SCL...