MDR1 gene expression and treatment outcome in small cell lung cancer: MDR1 gene expression as an independent prognostic factor.

We report a preliminary study to determine whether MDR1 gene expression level in small cell lung cancer (SCLC) tumors is a useful predictor of tumor response to chemotherapy and patient survival in association with myc amplification in the tumor. We analyzed 18 patients with SCLC receiving adriamycin and etoposide combination chemotherapy between August 1989 and November 1991; 16 males and 2 females, median age of 68 years, and 7 with limited disease and 11 with extensive disease. MDR1 mRNA expression level and myc family gene amplification were simultaneously determined by polymerase chain reaction using transbronchial biopsy specimens which were obtained at diagnosis. Patients with tumors expressing low MDR1 mRNA responded more favorably to chemotherapy than those with tumors expressing high MDRI mRNA, however, the difference in tumor response was statistically not significant (84.6% versus 40%). The overall survival was significantly shorter in the latter than in the former (7.2 months versus 11.7 months; p = 0.023). The survival of the 4 patients with tumor showing myc family gene amplification was almost identical to that of patients with tumors showing no amplification of the gene (8.2 months versus 8.8 months; p = 0.73). Multivariate Cox's regression analysis supports the notion that MDR1 may be a useful independent prognostic factor.