Objectives: We aimed to reconstitute T2 and T3 stage classification in nasopharyngeal carcinoma (NPC) cases and verify its utility in clinical settings.
Materials and methods: We enrolled 792 NPC patients. Cox proportional hazards model was used to compare the effect sizes (hazard ratio [HR]) of the cranial structure invasion on survival and select the structures for up-staging or downstaging T2 and T3 NPC. The samples were reclassified and the survival curves for T2 and T3 stages were analyzed. The proposed new staging system was validated on an external sample (n = 433).
Results: Thirteen cranial structures were examined. American Joint Committee on Cancer (AJCC) T3 stage patients with the invasion of the base of the sphenoid (HR = 2.58, 95% CI = 1.16-5.77) or base of the pterygoid (HR = 2.00, 95% CI = 0.84-4.77) had significantly lower hazard ratios than T2 stage patients with the invasion of soft tissues in the bilateral parapharyngeal space (HR = 5.26, 95% CI = 2.02-13.68) and single/bilateral carotid sheath (HR = 7.78, 95% CI = 3.06-19.76). T3 stage with the invasion of the above-mentioned bones was reclassified as T2, and T2 stage with the invasion of the above-mentioned soft-tissue structures was reclassified as T3. Survival analysis showed a significant difference between the reclassified T2 and T3 stages (P < 0.001). The results were replicated in the validation samples.
Conclusion: The proposed staging system for defining T2 and T3 stage NPC appears to be superior to the AJCC 8th edition. It could improve prognosis and optimize the treatment selection.
Keywords: AJCC stage system; MRI imaging; T staging; nasopharyngeal carcinoma; survival analysis.
© 2020 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.