Quantitative Metastatic Lymph Node Regions on Magnetic Resonance Imaging Are Superior to AJCC N Classification for the Prognosis of Nasopharyngeal Carcinoma

Prognostic nomograms for nasopharyngeal carcinoma with nodal features and potential indication for N staging system: Validation and comparison of seven N stage schemes

PURPOSE

To identify the prognostic value of the nodal features, propose a nomogram-based N stage system and evaluate the performance of seven N stage schemes of nasopharyngeal carcinoma (NPC) patients.

METHODS

Data from 1638 non-distant metastatic NPC patients were used to develop nomograms predicting 3-year and 5-year overall survival (OS) and distant metastasis-free survival (DMFS). Based on nomogram and multivariate analyses, a new N-stage scheme was proposed. The performance of the nomogram-based N staging system was assessed against five newly proposed N staging systems and the current 8th N staging system using a quantitative model to compare hazard consistency, discrimination, outcome prediction, and sample size balance. The Kaplan-Meier method with log-rank tests was used to compare survival differences.

RESULTS

Nomograms to predict OS and DMFS were constructed using extranodal extension infiltrating the surrounding structures (ENEmax), maximal axial diameter (MAD), large retropharyngeal lymph nodes (RLN, minimal axial diameter > 1.5 cm), multiple central nodal necrosis (CNN), and total lymph node (LN) number and level. Multivariate analysis showed the independent prognostic value of ENEmax and MAD > 3 cm for all selected survival endpoints (p < 0.05). Large RLN and lower neck involvement were independently associated with OS (p < 0.05). We proposed using a large RLN and MAD > 3 cm as N2 factors, and ENEmax and lower neck involvement as N3 factors. Among the seven N-stage schemes, our nomogram-based N scheme and ENEmax to N3 scheme (ENE3) ranked in the top two in the overall comparison with the elevated outcome predicting value (highest c-index). However, between the N0, N1, N1, and N2 subgroups, the ENE3 scheme showed no difference in OS or DMFS (p > 0.05).

CONCLUSION

The predictive model highlighted the independent prognostic value of ENEmax, cervical lymph node, MAD, and large RLN, which can be used as criteria for future N staging.

MRI-Based Metastatic Nodal Number and Associated Nomogram Improve Stratification of Nasopharyngeal Carcinoma Patients: Potential Indications for Individual Induction Chemotherapy

BACKGROUND

Metastatic lymph nodal number (LNN) is associated with the survival of nasopharyngeal carcinoma (NPC); however, counting multiple nodes is cumbersome.

PURPOSE

To explore LNN threshold and evaluate its use in risk stratification and induction chemotherapy (IC) indication.

STUDY TYPE

Retrospective.

POPULATION

A total of 792 radiotherapy-treated NPC patients (N classification: N0 182, N1 438, N2 113, N3 59; training group: 396, validation group: 396; receiving IC: 390).

FIELD STRENGTH/SEQUENCE

T1-, T2- and postcontrast T1-weighted fast spin echo MRI at 1.5 or 3.0 T.

ASSESSMENT

Nomogram with (model B) or without (model A) LNN was constructed to evaluate the 5-year overall (OS), distant metastasis-free (DMFS), and progression-free survival (PFS) for the group as a whole and N1 stage subgroup. High- and low-risk groups were divided (above vs below LNN- or model B-threshold); their response to IC was evaluated among advanced patients in stage III/IV.

STATISTICAL TESTS

Maximally selected rank, univariate and multivariable Cox analysis identified the optimal LNN threshold and other variables. Harrell's concordance index (C-index) and 2-fold cross-validation evaluated discriminative ability of models. Matched-pair analysis compared survival outcomes of adding IC or not. A P value < 0.05 was considered statistically significant.

RESULTS

Median follow-up duration was 62.1 months. LNN ≥ 4 was independently associated with decreased 5-year DMFS, OS, and PFS in entire patients or N1 subgroup. Compared to model A, model B (adding LNN, LNN ≥ 4 vs <4) presented superior C-indexes in the training (0.755 vs 0.727) and validation groups (0.676 vs 0.642) for discriminating DMFS. High-risk patients benefited from IC with improved post-IC response and OS, but low-risk patients did not (P = 0.785 and 0.690, respectively).

CONCLUSIONS

LNN ≥ 4 is an independent risk stratification factor of worse survival in entire or N1 staging NPC patients. LNN ≥ 4 or the associated nomogram has potential to identify high-risk patients requiring IC.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: 4.

Prognostic significance of cervical radiologic carotid artery invasion by lymph node on magnetic resonance imaging in nasopharyngeal carcinoma

PURPOSE

Carotid artery invasion (CAI) has been demonstrated to be an important prognosticator in some head and neck cancers. This study aimed to examine the prognostic value of radiologic CAI (rCAI) by cervical lymphadenopathy in nasopharyngeal carcinoma (NPC).

METHODS

NPC patients treated between January 2013 and December 2016 were included. Pre-treatment MRIs were reviewed for cervical rCAI according to the radiologic criteria. Univariate and multivariate models were constructed to assess the association between cervical rCAI and clinical outcomes. A new N classification system was proposed and compared to the 8th AJCC system.

RESULTS

The percentage of patients with MRI-positive lymph nodes was 84.7% (494/583), of whom cervical rCAI cases accounted for 42.3% (209/494). Cervical rCAI was associated with significantly poorer OS, DFS, DFFS and RFFS compared to non-rCAI (P < 0.05). Multivariate analyses confirmed that cervical rCAI was an independent prognosticator for DFS and DFFS, surpassing other nodal features, such as laterality, size, cervical node necrosis (CNN) and radiologic extranodal extension (rENE), while location of positive LNs remained independently associated with OS, DFS and DFFS. We propose a refined N classification: New_N1: upper neck LNs only without cervical rCAI; New_N2: upper neck LNs only with cervical rCAI; New_N3: upper and lower LNs. The proposed classification broadened the differences in OS, DFS and DFFS between N1 and N2 disease, and achieved a higher c-index for DFS and DFFS.

CONCLUSIONS

Cervical rCAI was an independent unfavorable indicator of NPC. Compared to the AJCC system, the proposed N category showed satisfactory stratification between N1 and N2 disease, and better prediction of distant metastasis and disease failure.

The role of radiologic extranodal extension in predicting prognosis and chemotherapy benefit for T1-2 N1 nasopharyngeal carcinoma: A multicenter retrospective study

BACKGROUND AND PURPOSE

This multicenter retrospective study aimed to investigated the prognostic value of unequivocal radiologic extranodal extension (rENE) and the efficacy of chemotherapy for stage T1-2 N1 nasopharyngeal carcinoma (NPC) in the IMRT era.

MATERIALS AND METHODS

We included 1,082 patients treated in 2005-2017 from three centers. rENE was recorded as G1 (coalescent nodal mass comprising ≥ 2 inseparable nodes) or G2 (invading beyond perinodal fat to frankly infiltrate adjacent structures). Multivariable analysis (MVA) evaluated the prognostic value of rENE. The value of chemotherapy was assessed in rENE-positive (rENE + ) and rENE-negative (rENE - ) subset separately.

RESULTS

Centers 1, 2, and 3 had 139/515 (27.0 %), 100/365 (27.4 %), and 43/202 (21.3 %) cN + patients with rENE, respectively. Compared to rENE-, rENE + patients had a worse distant metastasis-free survival (DMFS) and overall survival (OS) (all p < 0.001). MVA confirmed the prognostic of both G1-rENE and G2-rENE for distant metastasis [G1: hazard ratio (HR): 2.933, G2: HR: 6.942, all p < 0.001] and death (G1: HR: 1.587, p = 0.040; G2: HR: 6.162, p < 0.001). There was no significant difference for DMFS and OS between chemo-radiotherapy and radiotherapy alone in rENE + and rENE - groups (all p > 0.1). However, rENE + patients with a cumulative cisplatin/nedaplatin dose (CCND) of > 160 mg/m² had an improved DMFS (p = 0.033) but no OS (p = 0.197).

CONCLUSION

Unequivocal rENE is prognostic in patients with T1-2 N1 NPC. Addition of chemotherapy to radiotherapy did not affect DMFS and OS in rENE - patients. Chemotherapy with a CCND of > 160 mg/m² improved DMFS in rENE + patients.

Quantitative Spatial Characterization of Lymph Node Tumor for N Stage Improvement of Nasopharyngeal Carcinoma Patients

This study aims to investigate the feasibility of improving the prognosis stratification of the N staging system of Nasopharyngeal Carcinoma (NPC) from quantitative spatial characterizations of metastatic lymph node (LN) for NPC in a multi-institutional setting. A total of 194 and 284 NPC patients were included from two local hospitals as the discovery and validation cohort. Spatial relationships between LN and the surrounding organs were quantified by both distance and angle histograms, followed by principal component analysis. Independent prognostic factors were identified and combined with the N stage into a new prognostic index by univariate and multivariate Cox regressions on disease-free survival (DFS). The new three-class risk stratification based on the constructed prognostic index demonstrated superior cross-institutional performance in DFS. The hazard ratios of the high-risk to low-risk group were 9.07 (p < 0.001) and 4.02 (p < 0.001) on training and validation, respectively, compared with 5.19 (p < 0.001) and 1.82 (p = 0.171) of N3 to N1. Our spatial characterizations of lymph node tumor anatomy improved the existing N-stage in NPC prognosis. Our quantitative approach may facilitate the discovery of new anatomical characteristics to improve patient staging in other diseases.

MRI-identified multidimensional nodal features predict survival and concurrent chemotherapy benefit for stage II nasopharyngeal carcinoma

BACKGROUND

Reliable predictors are urgently needed to identify stage II nasopharyngeal carcinoma (NPC) patients who could benefit from concurrent chemoradiotherapy (CCRT). We aimed to develop a nomogram integrating MRI-identified multidimensional features of lymph nodes to predict survival and assist the decision-making of CCRT for stage II NPC.

PATIENTS AND METHODS

This retrospective study enrolled 242 stage II NPC patients treated from January 2007 to December 2017. Overall survival (OS) was the primary endpoint. Performance of nomogram was evaluated using calibration curves, Harrell Concordance Index (C-index), area under the curve (AUC) and decision curves analysis (DCA) and was compared with TNM staging. According to the individualized nomogram score, patients were classified into two risk cohorts and therapeutic efficacy of CCRT were evaluated in each cohort.

RESULTS

Three independent prognostic factors for OS: age, number and location of positive lymph nodes were included into the final nomogram. T stage was also incorporated due to its importance in clinical decision-making. Calibration plots demonstrated a good match between the predicted and our observed OS rates. C-index for nomogram was 0.726 compared with 0.537 for TNM staging (p < 0.001). DCAs confirmed the superior clinical utility of nomograms compared with TNM staging. CCRT compared to intensity-modulated radiotherapy (IMRT) delivered OS benefit to patients in the high-risk group (5-year: 89.9% vs. 72.1%; 10-year: 72.5% vs. 34.2%, p = 0.011), but not in the low-risk group.

CONCLUSIONS

This lymph node features-based nomogram demonstrated excellent discrimination and predictive accuracy for stage II patients and could identify patients who can benefit from CCRT.

Prognostic value of quantitative cervical nodal necrosis burden on MRI in nasopharyngeal carcinoma and its role as a stratification marker for induction chemotherapy

OBJECTIVES

This study aimed to assess the prognostic value of quantitative cervical nodal necrosis (CNN) burden in N staging risk stratification in patients with nasopharyngeal carcinoma.

METHODS

Univariate and multivariate Cox regression models evaluated the association between lymph node variables based on MRI images and survival. Revisions for the N classification system were proposed and compared to the 8th edition AJCC staging system using Harrell's concordance index (C-index). The survival outcomes of induction chemotherapy plus concurrent chemoradiotherapy (CCRT) and CCRT alone in patients with multiple CNNs were compared.

RESULTS

In 1319 patients enrolled, CNN was not an independent prognostic factor for the main survival outcomes, but multiple CNNs (three or more necrotic nodes) were independent prognostic factors for distant metastasis-free survival (DMFS) (adjusted hazard ratio [HR], 2.05; p = 0.020) and progression-free survival (PFS) (HR, 1.78; p = 0.004), surpassing other nodal variables. On upgrading patients with multiple CNNs to revised N3 disease, the proposed N staging widened the differences in DMFS and PFS between N2 and N3 disease. The overall survival of patients with multiple CNNs who received CCRT plus induction chemotherapy was improved compared to that of those who received CCRT alone (76.1% vs. 55.7%; adjusted p = 0.030).

CONCLUSIONS

Upgrading patients with multiple CNNs to stage N3 may improve prognostication of the current AJCC staging system. Multiple CNNs might be a potential marker for stratifying patients who would benefit from induction chemotherapy.

KEY POINTS

• Quantitatively assessed the prognostic value of CNN burden in patients with NPC. • Upgrading patients with multiple CNNs to stage N3 may improve prognostication. • Multiple CNNs may be used as a stratification marker for induction chemotherapy.

Prognostic value of cervical nodal necrosis on staging imaging of nasopharyngeal carcinoma in era of intensity-modulated radiotherapy: a systematic review and meta-analysis

Purposes

To systematically review and perform meta-analysis to evaluate the prognostic value of cervical nodal necrosis (CNN) on the staging computed tomography/magnetic resonance imaging (MRI) of nasopharyngeal carcinoma (NPC) in era of intensity-modulated radiotherapy.

Methods

Literature search through PubMed, EMBASE, and Cochrane Library was conducted. The hazard ratios (HRs) with 95% confidence intervals (CIs) of CNN for distant metastasis-free survival (DMFS), disease free survival (DFS) and overall survival (OS) were extracted from the eligible studies and meta-analysis was performed to evaluate the pooled HRs with 95%CI.

Results

Nine studies, which investigated the prognostic values of 6 CNN patterns on MRI were included. Six/9 studies were eligible for meta-analysis, which investigated the CNN presence/absence in any nodal group among 4359 patients. The pooled unadjusted HRs showed that the CNN presence predicted poor DMFS (HR =1.89, 95%CI =1.72-2.08), DFS (HR =1.57, 95%CI =1.08-2.26), and OS (HR =1.87, 95%CI =1.69-2.06). The pooled adjusted HRs also showed the consistent results for DMFS (HR =1.34, 95%CI =1.17-1.54), DFS (HR =1.30, 95%CI =1.08-1.56), and OS (HR =1.61, 95%CI =1.27-2.04). Results shown in the other studies analysing different CNN patterns indicated the high grade of CNN predicted poor outcome, but meta-analysis was unable to perform because of the heterogeneity of the analysed CNN patterns.

Conclusion

The CNN observed on the staging MRI is a negative factor for NPC outcome, suggesting that the inclusion of CNN is important in the future survival analysis. However, whether and how should CNN be included in the staging system warrant further evaluation.

Prognostic Factors for Overall Survival in Nasopharyngeal Cancer and Implication for TNM Staging by UICC: A Systematic Review of the Literature

This study aims to identify prognostic factors in nasopharyngeal carcinoma (NPC) to improve the current 8th edition TNM classification. A systematic review of the literature reported between 2013 and 2019 in PubMed, Embase, and Scopus was conducted. Studies were included if (1) original clinical studies, (2) ≥50 NPC patients, and (3) analyses on the association between prognostic factors and overall survival. The data elements of eligible studies were abstracted and analyzed. A level of evidence was synthesized for each suggested change to the TNM staging and prognostic factors. Of 5,595 studies screened, 108 studies (44 studies on anatomical criteria and 64 on non-anatomical factors) were selected. Proposed changes/factors with strong evidence included the upstaging paranasal sinus to T4, defining parotid lymph node as N3, upstaging N-category based on presence of lymph node necrosis, as well as the incorporation of non-TNM factors including EBV-DNA level, primary gross tumor volume (GTV), nodal GTV, neutrophil-lymphocyte ratio, lactate dehydrogenase, C-reactive protein/albumin ratio, platelet count, SUVmax of the primary tumor, and total lesion glycolysis. This systematic review provides a useful summary of suggestions and prognostic factors that potentially improve the current staging system. Further validation studies are warranted to confirm their significance.

The prognostic value of radiologic extranodal extension in nasopharyngeal carcinoma: Systematic review and meta-analysis

OBJECTIVES

The prognostic value of radiologic extranodal extension (rENE) in nasopharyngeal carcinoma remains controversial. In this study, a meta-analysis was performed to assess the prognostic value of ungraded rENE and unambiguous advanced rENE.

METHODS

A literature search through PubMed, Cochrane Library, EMBASE and manual searches was conducted until May 2021. The adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival and distant metastasis-free survival were extracted and pooled.

RESULTS

Nine eligible studies were published between 2012 and 2021. The pooled patient number was 7532 (range 61-1887). Seven studies were eligible for the analysis of ungraded rENE, while 3 studies were eligible for unambiguous advanced rENE. The results showed that ungraded rENE was associated with worse overall survival (HR 1.85, 95% CI 1.04-3.27) and significantly associated with worse distant metastasis-free survival (HR 2.07, 95% CI 1.36-3.13). On the other hand, unambiguous advanced rENE was significantly associated with worse overall survival (HR 2.62, 95% CI 2.12-3.25) and worse distant metastasis-free survival (HR 3.14, 95% CI 1.85-5.33).

CONCLUSIONS

In nasopharyngeal carcinoma, both ungraded and unambiguous advanced rENE are significant prognosticators of overall survival and distant metastasis-free survival. More prospective studies are required to determine its role in risk stratification or clinical staging.

The evolution of the nasopharyngeal carcinoma staging system over a 10-year period: implications for future revisions

BACKGROUND

The classification criteria and staging groups for nasopharyngeal carcinoma described in the Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) staging system have been revised over time. This study assessed the proportion of patients whose staging and treatment strategy have changed due to revisions of the UICC/AJCC staging system over the past 10 years (ie, from the sixth edition to the eighth edition), to provide information for further refinement.

METHODS

We retrospectively reviewed 1901 patients with non-metastatic nasopharyngeal carcinoma treated in our cancer center between November 2009 and June 2012. The Akaike information criterion and Harrell concordance index were applied to evaluate the performance of the staging system.

RESULTS

In total, 25 (1.3%) of the 1901 patients who were staged as T2a according to the sixth edition system were downgraded to T1 in the eighth edition; 430 (22.6%) staged as N0 in the sixth edition were upgraded to N1 in the eighth edition; 106 (5.6%) staged as N1/2 in the sixth edition were upgraded to N3 in the eighth edition. In addition, 51 (2.7%) and 25 (1.3%) of the study population were upstaged from stage I to stage II and stage II to stage IVa, respectively; 10 (0.5%) was downgraded from stage II to stage I. The survival curves of adjacent N categories and staging groups defined by eighth classification system were well-separated. However, there was no significant difference in the locoregional failure-free survival (P = 0.730) and disease-free survival (P = 0.690) rates between the T2 and T3 categories in the eighth edition classification system.

CONCLUSIONS

Modifications to the tumor-node-metastasis staging system over the past 10 years have resulted in N classification changes in numerous cases. Although the eighth edition tumor-node-metastasis staging system better predicts survival outcomes, the T classification could be simplified in future revisions.

Long Noncoding RNA OIP5-AS1 Promotes the Disease Progression in Nasopharyngeal Carcinoma by Targeting miR-203

Nasopharyngeal carcinoma (NPC) is a kind of malignancy generated from the nasopharyngeal epithelium. Recently, long noncoding RNA (lncRNA) has been shown to be involved in the regulation of many signaling pathways and is closely associated with carcinogenesis and tumor progression. However, the precise role of lncRNA Opa-interacting protein 5 antisense RNA 1 (OIP5-AS1) in NPC is not well understood. Here, we find that OIP5-AS1 is overexpressed in NPC patient specimens and NPC cell lines. Further investigations reveal that knockdown of OIP5-AS1 significantly inhibits the proliferation, migration, and invasion and accelerates the apoptosis of NPC cells in vitro. Consistent with these findings, NPC progression is significantly slowed in mice when OIP5-AS1 is knocked down. Interestingly, there is a functional link between OIP5-AS1 and microRNA-203 (miR-203), a tumor suppressor, in NPC cells. In conclusion, our data demonstrate that OIP5-AS1 plays an important role in the development and progression of NPC by targeting miR-203 and therefore provide a promising target for the treatment of NPC.

Simultaneous targeting of primary tumor, draining lymph node, and distant metastases through high endothelial venule-targeted delivery

Cancer patients with malignant involvement of tumor-draining lymph nodes (TDLNs) and distant metastases have the poorest prognosis. A drug delivery platform that targets the primary tumor, TDLNs, and metastatic niches simultaneously, remains to be developed. Here, we generated a novel monoclonal antibody (MHA112) against peripheral node addressin (PNAd), a family of glycoproteins expressed on high endothelial venules (HEVs), which are present constitutively in the lymph nodes (LNs) and formed ectopically in the tumor stroma. MHA112 was endocytosed by PNAd-expressing cells, where it passed through the lysosomes. MHA112 conjugated antineoplastic drug Paclitaxel (Taxol) (MHA112-Taxol) delivered Taxol effectively to the HEV-containing tumors, TDLNs, and metastatic lesions. MHA112-Taxol treatment significantly reduced primary tumor size as well as metastatic lesions in a number of mouse and human tumor xenografts tested. These data, for the first time, indicate that human metastatic lesions contain HEVs and provide a platform that permits simultaneous targeted delivery of antineoplastic drugs to the three key sites of primary tumor, TDLNs, and metastases.

Low value of whole-body dual-modality [18f]fluorodeoxyglucose positron emission tomography/computed tomography in primary staging of stage I-II nasopharyngeal carcinoma: a nest case-control study

Objectives

The value of using PET/CT for staging of stage I–II NPC remains unclear. Hence, we aimed to investigate the survival benefit of PET/CT for staging of early-stage NPC before radical therapy.

Methods

A total of 1003 patients with pathologically confirmed NPC of stages I–II were consecutively enrolled. Among them, 218 patients underwent both PET/CT and conventional workup ([CWU], head-and-neck MRI, chest radiograph, liver ultrasound, bone scintigraphy) before treatment. The remaining 785 patients only underwent CWU. The standard of truth (SOT) for lymph node metastasis was defined by the change of size according to follow-up MRI. The diagnostic efficacies were compared in 218 patients who underwent both PET/CT and CWU. After covariate adjustment using propensity scoring, a cohort of 872 patients (218 with and 654 without pre-treatment PET/CT) was included. The primary outcome was overall survival based on intention to treat.

Results

Retropharyngeal lymph nodes were metastatic based on follow-up MRI in 79 cases. PET/CT was significantly less sensitive than MRI in detecting retropharyngeal lymph node lesions (72.2% [62.3–82.1] vs. 91.1% [84.8–97.4], p = 0.004). Neck lymph nodes were metastatic in 89 cases and PET/CT was more sensitive than MRI (96.6% [92.8–100.0] vs. 76.4% [67.6–85.2], p < 0.001). In the survival analyses, there was no association between pre-treatment PET/CT use and improved overall survival, progression-free survival, local relapse-free survival, regional relapse-free survival, and distant metastasis-free survival.

Conclusions

This study showed PET/CT is of little value for staging of stage I–II NPC patients at initial imaging.

Key Points

• PET/CT was more sensitive than MRI in detecting neck lymph node lesions whereas it was significantly less sensitive than MRI in detecting retropharyngeal lymph node lesions.

• No association existed between pre-treatment PET/CT use and improved survival in stage I–II NPC patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-020-07478-1.

Prognostic significance of quantitative metastatic lymph node burden on magnetic resonance imaging in nasopharyngeal carcinoma: A retrospective study of 1224 patients from two centers

BACKGROUND AND PURPOSE

The number of metastatic lymph nodes (LNs) has been demonstrated to be an important prognosticator in some head and neck cancers. This study aimed to examine its prognostic value in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

Patients with newly-diagnosed, non-distant metastatic NPC from two centers were enrolled in this study. According to the radiologic criteria for involved LNs, the number of positive LNs was assessed on MRI. Univariate and multivariate models were constructed to assess the association between the number of positive LNs and clinical outcomes. Exhaustive method was used to determine the cutoff values of the number of positive LNs.

RESULTS

In 1224 patients, the number of MRI-positive LNs was an independent risk factor for overall survival (OS), distant metastasis-free survival (DMFS), relapse-free survival (RFS), progression-free survival (PFS) and regional relapse-free survival (RRFS), surpassing other nodal factors. All the patients were divided into no, low (1-4 positive LNs), moderate (5-9 positive LNs) and high (>9 positive LNs) risk groups. The HRs of high-risk group exceeded the HRs of N3 classification for OS, DMFS, RFS, PFS and RRFS. On upgrading patients with more than 9 positive LNs from N2 to N3, the revised N-staging system showed a higher C-index compared to current N-staging system for predicting OS (0.747 vs. 0.741, P = 0.002), RFS (0.655 vs. 0.640, P = 0.015) and PFS (0.674 vs. 0.669, P = 0.035).

CONCLUSIONS

The number of MRI-positive LNs was a predominant independent prognostic factor for NPC patients' survival. It may be incorporated into the future N-staging system to improve its accuracy in predicting outcomes.