Pleural invasion, epidermal growth factor receptor mutation and carcinoembryonic antigen level affect pleural lavage cytology-positive status in non-small-cell lung cancer

OBJECTIVES Pleural invasion (pl) is strongly associated with the pleural lavage cytology (PLC) status. We analysed tumours with pl and evaluated the relationship between the PLC status and pl. METHODS We retrospectively reviewed 428 surgically treated patients who had been diagnosed with non-small-cell lung cancer with pl and had their PLC status examined between 2000 and 2016. We investigated the influence of a PLC-positive status on the prognosis and searched for the factors predictive of a PLC-positive status. RESULTS Seventy-eight (18%) patients were PLC positive. The recurrence-free survival of PLC-positive patients was significantly worse than that of PLC-negative patients in pl1 and pl2, but not in pl3 (5-year recurrence-free survival rate, PLC positive versus PLC negative: pl1, 22.0% vs 60.0%, P = 0.002; pl2, 30.4% vs 59.7%, P = 0.015; pl3, 50.0% vs 59.6%, P = 0.427). A multivariable analysis showed that the degree of pl (pl2–3 versus pl1) [odds ratio (OR) 5.34, P < 0.001] was an independent predictive factor for PLC positivity. Epidermal growth factor receptor (EGFR) mutation positivity (OR 5.48, P = 0.042) and carcinoembryonic antigen (CEA) ≥5 ng/ml (OR 3.78, P = 0.042) were associated with a PLC-positive status in patients with pl2–3. We found that the PLC-positive rate in patients with pl2–3 was 35.6%; however, if the tumour was EGFR mutation positive and had CEA ≥5 ng/ml, the PLC-positive rate increased to 77%. CONCLUSIONS If a tumour was suspected of being pl2–3 and had EGFR mutation positivity and CEA ≥5 ng/ml, the PLC-positive rate was extremely high. Clinical trial registration number Hyogo Cancer Center, G-138.