Effects Of Evaluating Metastatic Cervical Lymph Node Maximum Diameter And Levels By Different Methods In N Staging Of Nasopharyngeal Carcinoma

Purpose Comparing the differences in evaluating metastatic cervical lymph node maximum diameter(MAD) and levels by magnetic resonance imaging(MRI) and clinical palpation, and exploring the effects of measuring nodal MAD on MRI and using MRI-based radiological criteria to define nodal levels for N-staging of nasopharyngeal carcinoma(NPC).Methods A total of 1197 consecutive patients with newly diagnosed, biopsy-proven, and non-metastatic NPC were retrospectively analyzed. All of them received intensity-modulated radiotherapy(IMRT) at Fujian Provincial Cancer Hospital from June 2005 to December 2010. On the basis of the seventh version UICC/AJCC staging system, lymph nodes were restaged by the following two different staging criteria:(1) measuring lymph nodal MAD by palpation and evaluating nodal levels depending on whether there is palpation-based supraclavicular fossa(SCF) lymph node invasion;(2) measuring lymph nodal MAD on MRI and replacing SCF with radiological criteria(IV, Vb) to evaluate nodal levels. The N-staging subgroup distributions by two different staging criteria were compared, and kappa index was calculated to check the consistency of them. The actuarial rates were evaluated by the Kaplan-Meier methods, and compared with the log-rank test. Endpoints including overall survival(OS) and distant metastasis-free survival(DMFS) were analyzed. SPSS 19.0(SPSS Inc. Chicago, IL, USA) was used for all statistical analysis.Results Nodal metastasis occurred in 1027 of 1197 patients(85.8%) in this study. Of whom, retropharyngeal lymph node(RLN) and level II were invaded most commonly with an incidence of 86.3%(886 of 1027) and 82.8%(850 of 1027) respectively, followed by level III(21.1%), level Va(8.4%), level IV(5.7%), level Vb(3.0%) and level I(2.2%). Additionally, 31 cases(3.0%) had a nodal MAD > 6 cm by palpation while this figure ascended to 63(6.1%) on MRI. Palpation-based supraclavicular fossa(SCF) invasion was found in 36 cases(3.5%), but 79 cases(7.7%) had levels IV or Vb involvement when using radiological criteria. Consequently, compared with clinical palpation, a total number of 60 patients(24 cases of N1, 36 cases of N2) were upstaged into N3 stage when using MRI to assess nodal MAD and levels, while 8 cases with N3 stage were reclassified as N1(4 cases) and N2(4 cases), which led to changes in 7.6% of N stage cases, with a coincidence rate of 92.4%(k = 0.85, p ï¿¡ 0.001) between the two staging criteria. Overall, the 5-year OS and DMFS rates for the whole group were 81.5% and 82.5%. In univariate analysis, Nodal MAD > 6 cm by palpation had no significant effect for overall survival(OS) and distant metastasis-free survival(DMFS)(both p > 0.05), but nodal MAD > 6 cm on MRI had prognostic significance for DMFS(p = 0.01). SCF invasion was a significant prognostic factor for DMFS(p = 0.002), but not for OS(p = 0.088). However, levels IV or Vb lymph node metastasis had prognostic significance for both OS(p = 0.034) and DMFS(p = 0.003).Conclusions Compared with clinical palpation, evaluating nodal MAD and levels by MRI resulted in a high proportion of N3 stage and a more balanced N-staging subgroup distribution. Although the prognostic values of N-staging for OS and DMFS based on MRI and palpation were analogous, the former was more accurate and was more suitable for precise radiotherapy.