N-cadherin, E-cadherin, ERCC1, and c-kit expression in small cell lung cancer (SCLC) and potential for new therapeutic targets
e22157 Background: Minimal advances have been made in the treatment of SCLC. Molecular markers may allow us to better stratify patients (pts) for new treatment options and drug combinations. The objective of our study was to determine the frequency and potential prognostic significance of N-cadherin (N-cad), E-cadherin (E-cad), ERCC1, and c-kit (CD117) expression in SCLC. Methods: Tissue from 132 pts with SCLC was retrospectively stained for N-cad, E-cad, ERCC1, and c-kit. Frequency of expression (% of tumor cells staining positive) was measured on a scale of 0–4 (freq 0=no expression (<1%), freq 1=1–10%, freq 2=11–35%, freq 3=36–70%, freq 4=71–100%). Charts were reviewed for stage, performance status, date of diagnosis/death, survival, and treatment (type, dates, response). The frequency of molecular markers was correlated with clinical data and overall survival. Results: Age range 42 to 97 years, 65 male:67 female, and 64 had limited and 68 had extensive stage. Of the 132 pts, 75% had tumors that expressed (frequency ≥ 1) N-cad, 58% E-cad, 70% ERCC1, and 55% c-kit. Comparing tumor marker expression with survival using either the Log-Rank Test or the Wilcoxon Test, there was no significant association for N-cad, E-cad, or ERCC1. However, tumors that expressed c-kit with frequency ≥ 3 had a trend toward superior survival compared with frequency < 3. Median survival for c-kit frequency ≥ 3 was 496 days compared to 312 days for frequency < 3 (p = 0.09, Log-Rank Test). Conclusions: In our retrospective study of 132 SCLC pts, we found that all 4 markers were expressed in greater than 50% of specimens, and that higher c-kit expression was associated with marginally significant increase in overall survival. Though previous experience with imatinib alone or with chemotherapy showed limited clinical activity in unselected SCLC pts, given preclinical synergy with cisplatin, it seems reasonable to consider combination therapy with cisplatin/etoposide and imatinib in pts selected for high c-kit expression. [Table: see text] No significant financial relationships to disclose.