Risk-stratified management of stage IB nasopharyngeal carcinoma under the 9th edition TNM staging system: a prognostic nomogram integrating MRI nodal features and Epstein–Barr virus DNA

Under the 9th edition AJCC/UICC staging system, Stage IB nasopharyngeal carcinoma (NPC, T1-2N1M0) represents a biologically heterogeneous population for which uniform chemoradiotherapy may be suboptimal. We aimed to develop a prognostic nomogram integrating MRI nodal features and plasma EBV DNA for individualised prognostic risk stratification. 446 consecutive TNM-9 stage IB NPC patients treated with intensity-modulated radiotherapy (IMRT) with or without chemotherapy between July 2016 and December 2023 were retrospectively analysed. Pretreatment MRI was assessed for radiologic extranodal extension (rENE) and lymph node necrosis (LNN). The nomogram was internally validated using bootstrap resampling. With a median follow-up of 43 months and 42 PFS events, 5-year PFS and OS were 87.6% and 96.0%, respectively. On multivariable analysis, rENE (HR 2.19, 95% CI 1.15–4.19, P = 0.019) and LNN (HR 2.22, 95% CI 1.16–4.26, P = 0.018) were independent predictors of inferior PFS. Tertile-based stratification identified low-, medium-, and high-risk groups with 5-year PFS rates of 100%, 85.6%, and 75.3%, respectively ( P < 0.001). No PFS events occurred in low-risk patients regardless of treatment; among high-risk patients, significant heterogeneity was observed across treatment modalities, with a numerically lower PFS event rate in patients receiving CCRT plus additional chemotherapy than in those receiving CCRT alone. This nomogram effectively stratifies TNM-9 stage IB NPC patients into distinct risk tiers, while exploratory treatment comparisons suggest potential treatment de-escalation in low-risk patients and warrant further evaluation of additional systemic chemotherapy in high-risk patients. Prospective validation is warranted. Not applicable.