Maintained sensitivity to EGFR tyrosine kinase inhibitors in EGFR-mutant lung cancer recurring after adjuvant erlotinib or gefitinib

PURPOSE

Given the unprecedented efficacy of EGFR tyrosine kinase inhibitors (TKI) in advanced EGFR-mutant lung cancer, adjuvant TKI therapy is an appealing strategy. However, there are conflicting findings regarding the potential benefit of adjuvant EGFR-TKI in patients with lung cancer harboring EGFR mutations. To better understand these results, we studied the natural history of lung cancers which recurred despite adjuvant TKI.

EXPERIMENTAL DESIGN

Patients with recurrent EGFR-mutant lung cancer following adjuvant TKI were identified using an Institutional Review Board-approved mechanism. Recurrent cancer specimens were tested for resistance mutations. Sensitivity to retreatment with EGFR-TKI was evaluated.

RESULTS

Twenty-two patients with cancers harboring an EGFR sensitizing mutation received adjuvant erlotinib or gefitinib for a median of 17 months (range 1-37 months). T790M was more common in cancers which recurred while receiving TKI than in those which recurred after stopping TKI (67% vs. 0%, P = 0.011). Fourteen patients who developed recurrence after stopping EGFR-TKI were retreated, with a median time to progression of 10 months and radiographic response seen in 8 of 11 patients with evaluable disease (73%).

CONCLUSIONS

Recurrence of EGFR-mutant lung cancer after stopping adjuvant TKI should not preclude a trial of TKI retreatment; a phase II trial of erlotinib in this setting is underway. Studies of adjuvant EGFR-TKI will underestimate the potential survival benefit of adjuvant TKI for patients with EGFR-mutant lung cancers if retreatment at recurrence is not given.

Impact on disease-free survival of adjuvant erlotinib or gefitinib in patients with resected lung adenocarcinomas that harbor EGFR mutations

BACKGROUND

Patients with stage IV lung adenocarcinoma and epidermal growth factor receptor (EGFR) mutation derive clinical benefit from treatment with EGFR tyrosine kinase inhibitors (TKIs). Whether treatment with TKI improves outcomes in patients with resected lung adenocarcinoma and EGFR mutation is unknown.

METHODS

Data were analyzed from a surgical database of patients with resected lung adenocarcinoma harboring EGFR exon 19 or 21 mutations. In a multivariate analysis, we evaluated the impact of treatment with adjuvant TKI.

RESULTS

The cohort consists of 167 patients with completely resected stages I to III lung adenocarcinoma. Ninety-three patients (56%) had exon 19 del, 74 patients (44%) had exon 21 mutations, and 56 patients (33%) received perioperative TKI. In a multivariate analysis controlling for sex, stage, type of surgery, and adjuvant platinum chemotherapy, the 2-year disease-free survival (DFS) was 89% for patients treated with adjuvant TKI compared with 72% in control group (hazard ratio = 0.53; 95% confidence interval: 0.28-1.03; p = 0.06). The 2-year overall survival was 96% with adjuvant EGFR TKI and 90% in the group that did not receive TKI (hazard ratio: 0.62; 95% confidence interval: 0.26-1.51; p = 0.296).

CONCLUSIONS

Compared with patients who did not receive adjuvant TKI, we observed a trend toward improvement in DFS among individuals with resected stages I to III lung adenocarcinomas harboring mutations in EGFR exon 19 or 21 who received these agents as adjuvant therapy. Based on these data, 320 patients are needed for a randomized trial to prospectively validate this DFS benefit.

EGFR-mutated lung cancer: a paradigm of molecular oncology

The development of EGFR tyrosine kinase inhibitors for clinical use in non-small cell lung cancer and the subsequent discovery of activating EGFR mutations have led to an explosion of knowledge in the fields of EGFR biology, targeted therapeutics and lung cancer research. EGFR-mutated adenocarcinoma of the lung has clearly emerged as a unique clinical entity necessitating the routine introduction of molecular diagnostics into our current diagnostic algorithms and leading to the evidence-based preferential usage of EGFR-targeted agents for patients with EGFR-mutant lung cancers. This review will summarize our current understanding of the functional role of activating mutations, key downstream signaling pathways and regulatory mechanisms, pivotal primary and acquired resistance mechanisms, structure-function relationships and ultimately the incorporation of molecular diagnostics and small molecule EGFR tyrosine kinase inhibitors into our current treatment paradigms.