Impact of Positive Pleural Lavage Cytology on Survival in Patients Having Lung Resection for Non-small-cell Lung Cancer: An International Individual Patient Data Meta-analysis

Objectives: Pleural lavage cytology is the microscopic study of cells obtained from saline instilled into and retrieved from the chest during surgery for non-small-cell lung cancer. The aims of this study were to collate multi-institutional individual patient data for meta-analysis to determine independence as a prognostic marker and to characterize the impact of positive results on stage-adjusted survival.

Methods: We identified 31 publications from 22 centers/research groups that performed pleural lavage cytology during surgery for non-small-cell lung cancer and invited submission of individual patient data. Actuarial survival was calculated using Kaplan-Meier methods, and comparisons were performed using the log-rank test. Cox proportional hazards regression was used to ascertain the covariates associated with survival.

Results: By January 1, 2008, submissions were received internationally from 11 centers with individual data from 8763 patients. In total, 511 (5.8%) patients had a positive pleural lavage cytology result, and this was shown to be an independent predictor of adverse survival associated with a hazard ratio of 1.465 (1.290-1.665; P < .001) compared with a reference hazard ratio of 1 for a negative result. On statistical modeling, the best adjustment for patients with a positive pleural lavage cytology result was a single increase in the T category assigned to the case, up to a maximum of T4. Correction for differences in survival were obtained in stages IB (P = .315) and IIB (P = .453), with a degree of correction in stage IIIA (P = .07).

Conclusions: Pleural lavage cytology should be considered in all patients with non-small-cell lung cancer suitable for resection. A positive result is an independent predictor of adverse survival, and the impact on survival suggests that it may be appropriate to upstage patients by 1 T category.