Introduction: A recent large randomized controlled trial revealed that patients with lung cancer with epidermal growth factor receptor (EGFR) mutations had better prognoses when treated with the EGFR-tyrosine kinase inhibitor, gefitinib, than with cytotoxic chemotherapeutic agents. Lung cancer with EGFR mutations is highly sensitive to EGFR-tyrosine kinase inhibitors. The previous trial implied that EGFR mutations might be predictive of the response to cytotoxic chemotherapy.
Methods: Forty-six tumor tissue specimens (32 adenocarcinomas and 14 nonadenocarcinomas) were obtained from patients with lung cancer who underwent surgical resection. EGFR mutations were detected using polymerase chain reaction-invader assay. A histoculture drug response assay was used as an in vitro drug sensitivity test. The inhibition rates of cisplatin, docetaxel (DOC), vinorelbine, and gemcitabine were measured.
Results: Sensitizing EGFR mutations were detected in samples from 14 patients, all with adenocarcinomas. The inhibition rate of cisplatin in tumors with EGFR mutations (group M) was 34.8 ± 15.5%, which was significantly lower (p = 0.0153) than in wild-type tumors (group W; 46.6 ± 14.0%). The inhibition rate of DOC in group M (18.8 ± 13.4%) was also significantly lower (p = 0.0051) than in group W (35.4 ± 19.1%). There were no significant differences in inhibition rates of gemcitabine and vinorelbine between groups M and W. Inhibition rates of DOC were significantly lower in group M (p = 0.0256) than in group W (32.6 ± 18.4) in samples from patients with adenocarcinoma.
Conclusion: The histoculture drug response assay indicated that lung cancers with EGFR mutations were less sensitive to DOC than EGFR wild-type tumors.