Chemotherapy resistance and oncogene expression in non-small cell lung cancer

Empiric chemotherapy for patients with non-small cell lung cancer who have undergone resection is recommended without knowledge of the tumor's specific biologic characteristics, and many patients may not benefit. In vitro chemotherapy resistance is associated with clinical unresponsiveness in some tumors, and in lung cancer, chemotherapy resistance is prevalent. Multiple-agent chemotherapy resistance and association of chemotherapy resistance with molecular markers are described.

Chemotherapy resistance to doublets--carboplatin and paclitaxel, cisplatin and navelbline, cisplatin and docetaxel, and cisplatin and gemcitabine--was analyzed in 4571 non-small cell lung cancer tumors with the extreme drug resistance assay. Chemotherapy resistance is defined as follows: extreme drug resistance, 1 SD above the median chemotherapy resistance; intermediate drug resistance, between the median and extreme drug resistances; and low drug resistance, 1 SD below the median. Chemotherapy resistance was compared with DNA ploidy measured by flow cytometry, and markers p53 and epithelial growth factor receptor were assayed by immunohistochemistry.

Tumors with extreme or intermediate drug resistance were noted in 30% to carboplatin-paclitaxel, in 24% to cisplatin-navelbline, in 42% to cisplatin-gemcitabine, and in 27% to cisplatin-docetaxel. Extreme or intermediate drug resistance to at least one drug occurred in 74% to carboplatin-paclitaxel, in 68% to cisplatin-navelbline, in 88% to cisplatin-gemcitabine, and in 68% to cisplatin-docetaxel. More intermediate plus extreme chemotherapy resistances occurred in aneuploid tumors to etoposide (53% vs 36%, P = .0002) and topotecan (48% vs 36%, P = .0094), with less intermediate or extreme chemotherapy resistance to gemcitabine (88% vs 81%, P = .0345). p53-Positive tumors had more intermediate or extreme resistance to etoposide (57% vs 44%, P = .0009) and doxorubicin (73% vs. 58%, P = .0324) and less intermediate or extreme resistance to cisplatin (44% vs 54%, P = .0125), to carboplatin (47% vs 57%, P = .0129), to taxol (47% vs 57%, P = .0056), and to gemcitabine (78% vs 87%, P = .0108). Fewer epithelial growth factor receptor-positive tumors were extremely drug resistant to cisplatin (13% vs 26%, P = .0074) and carboplatin (13% v. 30%, P = .0008).

Multi-drug chemotherapy resistance in non-small cell lung cancer tumor cultures is common, and associations between molecular markers and in vitro chemotherapy resistance are noted. Clinical validation through integration of such testing into clinical trials seems warranted.