Prediction of Pleural Lavage Cytology According to Thin-Section Computed Tomography in Non–Small-Cell Lung Cancer

Although the positive rate of preresection pleural lavage cytology (PLC) is low, it is an important indicator of poor prognosis for non–small-cell lung cancer patients with frequent pleural dissemination (PD) recurrence. Thin-section computed tomography (TSCT) can reveal relationships between a primary tumor and the pleura at 1 to 2 mm intervals, and this is associated with visceral pleural invasion (VPI). However, its association with PLC remains unclear. Therefore, we aimed to improve PLC efficiency and predict PD recurrence by understanding the relationship between PLC and preoperative TSCT findings. Between January 2014 and December 2018, we reviewed 978 patients with non–small-cell lung cancer who underwent PLC tests during complete resection surgery. Preoperative TSCT findings were evaluated, and factors with the highest specificity (proportion of patients with radiologically to pathologically diagnosed positive PLC) were investigated. We also evaluated their relationships with VPI and PD recurrence. PLC positive was identified in 55 (5.6%) of the 978 patients. The two TSCT findings predicting PLC results, “the absence of pleural findings,” ie, tumor not attached to pleura or without pleural tag, and “consolidation-to-tumor ratio ≤0.5”, had a specificity of 100% (95% confidence interval: 90.4%-100%); additionally, all cases with these findings were VPI negative and had no PD recurrence. And 24% of the cohort had either of these findings. The absence of pleural findings and/or consolidation-to-tumor ratio ≤0.5 of primary tumor on preoperative TSCT can predict PLC negativity with very high probability; therefore, PLC can be omitted for such patients. The present study investigated the feasibility of omitting preresection pleural lavage cytology (PLC), on the basis of findings on preoperative thin-section computed tomography. All patients without pleural findings (pleural attachment or pleural tags) and/or with a consolidation-to-tumor ratio of ≤0.5 were PLC negative. Therefore, PLC assessment can be omitted for such patients.