Background: Amplification of the c-myc gene has been reported in non-small cell lung cancer (NSCLC). We investigated the c-myc gene amplification and the numerical aberration of chromosome 8 by dual color fluorescence in situ hybridization (FISH) to evaluate the relation between possible genetic abnormalities, pathological factors and prognosis.
Methods: Tumor tissue samples were obtained from 31 patients with NSCLC who underwent lobectomy with mediastinal lymph node dissection. Samples were analyzed by FISH using 8 alpha satellite DNA probe and c-myc gene cosmid probe. The relation between genetic abnormalities, pathological factors (T factor, tumor size, and N factor), and prognostic factors was evaluated by univariate and multivariate analysis, and by the Kaplan-Meier method and log-rank analysis.
Results: Chromosome 8 aberrations were T1 (n=3), 44.0%; T2 (n=18), 35.7%; T3 (n=7), 40.0%; T4 (n=3), 39.7% (p=NS). The c-myc gene amplifications were T1, 54.3%; T2, 51.1%; T3, 51.0%; T4, 66.3% (p=NS). There was no difference between patients whose tumor was more than 5 cm (n=16), and 5 cm or less (n=15) in the rate of chromosome 8 aberration (39.3%: 36.3%), or the rate of the c-myc gene amplification (52.1%: 53.7%). N factors for chromosome 8 aberrations were N0 (n=18), 35.9%; and N2 (n=11), 44.9% (p=NS). In the c-myc gene amplification, there was a significant difference between N0 and N2 (48.6%, 61.3%, p=0.040). In univariate and multivariate analysis, chromosome 8 aberrations correlated with a poor prognosis (p=0.037 and p=0.041). The 5-year survival rate was 15.4% in patients whose rate of chromosome 8 aberrations was 40% or more (n=13), which was significantly less than that in patients with an aberration rate of less than 40% (n=19, 57.9%, p=0.014).
Conclusion: The c-myc gene amplification correlates with lymph node metastasis. Although there was no significant link between the amplification of the c-myc gene and clinical outcome, the numerical chromosome 8 aberrations was considered to be a factor for survival.