Value of RASSF1A and SHOX2 methylation detection in intraoperative pleural lavage fluid for potential microdissemination and prognosis evaluation in non-small cell lung cancer

OBJECTIVE: To evaluate the potential of RASSF1A and SHOX2 methylation status in intraoperative pleural lavage (IPL) fluid for assessing invasiveness and predicting postoperative recurrence in non-small cell lung cancer (NSCLC). METHODS: Forty-three NSCLC patients who underwent lung tumor resection and IPL between November 2021 and June 2022 were prospectively enrolled. The patients included in the analysis did not receive adjuvant chemotherapy after surgery. Methylation of RASSF1A and SHOX2 in the IPL fluid was determined. Correlation of methylation status with clinicopathological or imaging features was assessed by Spearman correlation. Progression-free survival (PFS) and overall survival (OS) were compared by Kaplan-Meier curves and log-rank tests. Receiver operating characteristic curves evaluated the predictive performance of RASSF1A, SHOX2, and their combination for PFS. RESULTS: Positive methylation rates were 25.58% for RASSF1A, 27.91% for SHOX2, and 18.86% for combined detection. RASSF1A methylation positively correlated with neuron-specific enolase, CYFRA21-1, and imaging features (irregular tumor boundaries, lymph node enlargement, and tumor infiltration) (P < 0.01), and negatively with tumor density (solid) (P = 0.016). SHOX2 methylation correlated positively with CYFRA21-1 and imaging features (all P < 0.01). Kaplan-Meier analysis showed that the PFS of RASSF1A, SHOX2, and their combination positive patients was significantly shorter than that of the negative group (all P < 0.001). OS analysis also showed a similar trend, but due to the limited number of deaths, the relevant results need to be interpreted with caution. ROC analysis showed that the AUC of RASSF1A, SHOX2, and combined detection for predicting PFS were 0.817, 0.923, and 0.962, respectively, with the combined detection performing the best. CONCLUSION: RASSF1A and SHOX2 methylation in IPL fluid closely correlates with aggressive pathological features and unfavorable NSCLC prognosis. In an exploratory cohort without postoperative adjuvant therapy, combined testing showed potential value in stratifying the risk of postoperative recurrence and is more suitable as a supplementary molecular reference for postoperative adjuvant therapy decision-making and follow-up management. However, it still needs to be further validated in multi-center populations receiving standard treatment.