Background and objective: Both Krebs von den Lungen-6 (KL-6) and carcinoembryonic antigen (CEA) are known to be tumour markers in non-small cell lung cancer (NSCLC). The aim of the present study was to assess whether or not intrabronchial epithelial lining fluid (ELF) levels of these markers predicted tumour response better than serum levels in patients with advanced NSCLC treated with gefitinib. Methods: ELF samples were obtained both from near the tumour and from the contralateral lung using a bronchoscopic microsampling technique, before and 2 weeks after the start of gefitinib treatment. Serum samples were taken concurrently. Among the 22 patients enrolled in the study, 14 (64%) showed partial responses or stabilization of disease with gefitinib treatment (treatment responders), while 8 (36%) showed progression of disease (treatment non-responders), 4 weeks after the start of treatment. Results: ELF KL-6 levels near the tumour decreased significantly after 2 weeks in the treatment responders group (P = 0.011), whereas there was a marginal increase in the treatment non-responders group (P = 0.049). ELF CEA levels near the tumour decreased significantly after 2 weeks in the treatment responders group (P = 0.004), whereas there was no significant change in the treatment non-responders group. For both markers, neither the serum levels nor the levels in contralateral ELF showed any significant changes in either group of patients. Conclusions: Both KL-6 and CEA levels in ELF near the tumour predicted tumour response in NSCLC patients treated with gefitinib, whereas serum levels did not. Intrabronchial epithelial lining fluid levels of KL-6 and CEA near tumours, as assessed by bronchoscopic microsampling, predicted tumour response in patients with advanced non-small cell lung cancer who were treated with gefitinib, whereas serum levels did not.
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