A proposed grading scheme for predicting recurrence in medullary thyroid cancer based on the Ki67 index and metastatic lymph node ratio

Purpose The Ki67 index and lymph node ratio (LNR) have been proposed as components of alternative pathological classification schemes, but the most appropriate classification for patients with medullary thyroid cancer (MTC) remains unknown. The aim of the present study was to examine the usefulness of a new grading system combining the Ki67 index and LNR as a predictor of prognostic and disease-free survival (DFS) in MTC. Methods We conducted a retrospective study of patients with MTC who were registered at Sun Yat-sen University Cancer Center, Guangzhou, P. R. China from June 2003 to October 2021. The DFS rates were assessed using risk-adjusted Cox proportional hazard regression modeling to explore the relationship among pathological features, nutritional status and DFS. The Ki67 index (cutoff value: 5% and 10%) and LNR (cutoff value: 0.2 and 0.3) were combined to create a new grading system. Results In total, 101 matched patients were assessed. The integrated grading system showed better separation of Kaplan Meier (KM) curves for DFS. As the grading stage progressed, there was a significant stepwise decrease in DFS, which was better than Ki67, LNR and N staging alone. According to the grading system, the high-risk group had a worse prognosis. Conclusion The proposed grading scheme demonstrated a better prognostic performance in MTC patients than the Ki67, LNR and N staging alone. However, larger scale studies are needed to further verify our findings.