Serial changes in pleural lavage cytology during lung cancer surgery predict recurrence and pleural dissemination.

[PURPOSE] Pleural lavage cytology (PLC) is a recognized prognostic marker in non-small cell lung cancer (NSCLC); however, the impact of serial intraoperative changes remains unclear.

[METHODS] We retrospectively analyzed 439 patients who underwent curative NSCLC resection. PLC was performed at three intraoperative points: after thoracotomy (pre-PLC), after lung resection, and after lavage at chest closure (post-PLC). Associations between recurrence-free survival (RFS) and pleural dissemination were evaluated by a Kaplan-Meier analysis and Fine and Gray competing risks regression.

[RESULTS] Forty-one patients had at least one positive PLC result. RFS was the lowest in pre-PLC( +)/post-PLC( +) (n = 10), intermediate in pre-PLC(-)/post-PLC( +) (n = 11), and best in post-PLC( -) (n = 20). Importantly, post-PLC( -) patients included 13 patients with pre-PLC positivity, yet their RFS matched that of consistently negative cases (n = 398). The cumulative incidence of pleural dissemination exhibited a similar pattern. In a multivariate analysis, post-PLC positivity, but not pre-PLC positivity, independently predicted poor RFS (hazard ratio, 3.06; p < 0.001).

[CONCLUSION] Post-PLC, but not pre-PLC, provides decisive prognostic information for recurrence and pleural dissemination, likely reflecting residual lavage-resistant tumor clusters. Importantly, combining pre- and post-PLC results refines risk stratification and identifies the poorest-outcome subgroup that may benefit from adjuvant therapy.