2884 - Validation and Development of a Refined M1 Category for Nasopharyngeal Carcinoma Based on the Ninth-Version of AJCC/UICC TNM Staging System in the Immunotherapy Era: A Multicenter Cohort Study
Presenter(s)
H. Xu1, Y. Hu2, T. Xie3, L. Lu4, Z. Yan1, X. Chen1, L. Zhu1, C. Xie2, T. Lu5, J. G. Li5, J. Pan6, S. Lin1, X. Gong5, and Q. Guo6; 1Department of Radiation Oncology, Clinical Oncology School of Fujian Medical University, Fujian Cancer Hospital, Fuzhou, China, 2Department of Radiology, Sun Yat-Sen University Cancer Center, Guangzhou, China, 3Hubei Cancer Hospital, Wuhan, China, 4Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou, China, 5Department of Radiation Oncology, Jiangxi Cancer Hospital of Nanchang University, Nanchang, China, 6Department of Radiation Oncology, Clinical Oncology School of Fujian Medical University, Fujian Cancer Hospital, Fuzhou, Fujian, China
Purpose/Objective(s): To evaluate the applicability of the M1 category of the Ninth-version of AJCC/UICC TNM staging system (TNM-9) for M1 nasopharyngeal carcinoma (M1-NPC) in immunotherapy era and propose potential refinements.
Materials/Methods: M1-NPC patients who underwent palliative chemotherapy and immune checkpoint inhibitors (ICIs) between January 2019 and June 2023 across five institutions were included and re-staged according to TNM-9. Overall survival (OS) and Progression-free survival (PFS) were analyzed. A recursive partitioning analysis (RPA) model was employed to derive a new RPA-M1 category.
Results: Among the 472 patients included, 219 were M1a and 253 were M1b. With a median follow-up time of 27 months, the M1a subgroup exhibited significantly higher 2-year OS (90.4% vs. 73.7%) and PFS (69.2% vs. 40.6%) than M1b subgroup (all P<0.001), which was further confirmed by multivariate analysis (MVA). Additionally, number of involved organs was found to be another independent predictor. New RPA-M1 category were then developed: RPA-M1a (=3 metastatic lesions and confined to one single organ), RPA-M1b (=3 metastatic lesions but involving multiple organs or >3 lesions and confined to one single organ), and RPA-M1c (patients with >3 metastatic lesions and involving multiple organs), with 2-year OS rates of 91.5%, 81.4%, and 69.8%, respectively (P<0.05) and PFS rates of 72.4%, 54.3% and 29.1%, respectively (P<0.005). Compared to the M1 Category in TNM-9, RPA-M1 category had a lower Akaike Information Criterion (AIC) and a higher concordance index (C-index) for OS and PFS.
Conclusion: The M1 category in the TNM-9 is applicable in the immunotherapy era. The RPA-M1 category offers improve depiction of survival outcomes compared to TNM-9, allowing for more refined stratification of patient outcomes and individualized decision-tailoring.