The threonine-to-methionine substitution at amino acid position 790 (T790M) of the epidermal growth factor receptor (EGFR) gene has been reported in progressing lesions after gefitinib treatment in non-small cell lung cancer (NSCLC) that causes sensitive tumors to become resistant to gefitinib. Alternatively, the EGFR T790M mutation might be present in small fractions of tumor cells before drug treatment, and the tumor cells harboring the T790M mutation might be enriched during the proliferation after drug treatment. We developed a mutant-enriched PCR assay to detect small fractions of cells with T790M mutation and used this technique to detect mutations in 280 NSCLCs, including gefitinib-treated 95 cases. Although the direct sequencing detected only 1 T790M mutant case, the mutant-enriched PCR (confirmed to enrich one mutant out of 1 Â 10 3 wild-type alleles) detected 9 additional cases among 280 cases. As linkage to clinicopathologic factors, the T790M mutation showed no bias for sex, smoking status, or histology but was significantly more frequent in advanced tumors (9 of 111 cases) than in early-stage tumors (1 of 169 cases; P = 0.0013). Among gefitinib-treated cases, gefitinib-sensitive mutations were found in 30 cases. The T790M mutation was present in 3 of 7 no-responders with the gefitinib-sensitive mutation and was not present in 19 responders (P = 0.014). Our results indicate that the T790M mutation is sometimes present in a minor population of tumor cells during the development of NSCLC and suggest that the detection of small fractions of T790M mutant alleles may be useful for predicting gefitinib resistance of NSCLCs with sensitive EGFR mutations. (Cancer Res 2006; 66(16): 7854-8)

This study revealed the frequencies and periods of development from PGGNs and HGGNs into part-solid nodules. Invasive adenocarcinomas were diagnosed only among the part-solid nodules, corresponding to 1% of all 1229 SSNs.

EGFR and KRAS mutations occur early during the multistage pathogenesis of peripheral lung adenocarcinomas. By contrast, increased EGFR copy number is a late event during tumor development and plays a role in the progression of lung adenocarcinoma independent of the initiating molecular events.

The excision repair cross-complementation group 1 (ERCC1) and BRCA1 have been identified as predictors of clinical outcomes among patients with non-small-cell lung cancer (NSCLC) treated with cisplatin-based chemotherapy. In this study, we immunohistochemically examined the ERCC1 and BRCA1 protein expression levels in 35 patients with metastatic mediastinal lymph nodes obtained prior to treatment as retrospective study. These patients had been enrolled in our studies on neoadjuvant chemotherapy with cisplatin and irinotecan (15 patients) or chemoradiotherapy with cisplatin and docetaxel plus concurrent thoracic radiation (20 patients). The relations between the ERCC1 or BRCA1 protein expression and the clinical outcomes of the patients were then examined. The rates of radiological response and pathological effectiveness were significantly higher among patients with ERCC1-negative tumors, compared with those with positive tumors in the neoadjuvant chemotherapy group (radiological response rates; 100% vs. 42.8%, P=0.013; pathological effectiveness; 100% vs. 47.1%, P=0.038), but no associations were observed in the neoadjuvant chemoradiotherapy group. Regarding survival, no significant differences in overall survival or disease-free survival were observed between patients with ERCC1-negative and positive tumors in both the neoadjuvant chemotherapy and chemoradiotherapy groups. In summary, we showed that a ERCC1-negative protein status was significantly related to tumor responsiveness to neoadjuvant chemotherapy with cisplatin and irinotecan, but such a status was not a clear prognostic predictor to cisplatin-based neoadjuvant therapy in NSCLC patients. Further study is needed to clarify the value of molecular predictors for customizing therapy for patients with NSCLC.