Abstract
Purpose Quantitative lymph node burden has been demonstrated to be a critical prognosticator in various malignancies, yet it was seldom explored in nasopharyngeal carcinoma (NPC). This study aimed to investigate the impact of the number of metastatic lymph node regions (LRN) on prognosis of NPC and to establish a new N classification system based on LRN. Methods and Materials The magnetic resonance images (MRI) of 354 nondisseminated NPC patients before radical treatment were retrospectively evaluated. The regions with positive lymph nodes (LNs) were quantified according to 2013 updated guidelines for neck node levels. Prognostic value of LRN on distant metastasis-free survival (DMFS) was analyzed using multivariable Cox model after adjusting for other nodal characteristics and therapeutic factors. Results LRN strongly correlated with the size, laterality, level, extracapsular extension (ECE), and necrosis of LNs. Risk of distant metastasis significantly escalated with increased LRN (P<0.001). 5-year DMFS for LRN 0-1, 2-6, and ⩾7 was 97.0%, 86.7%, and 69.7%, respectively. In multivariable Cox analysis, LRN (HR 2.45; 95% CI 1.55-3.88; P<0.001) and maximal LN diameter (MLD) >6cm (HR 4.11; 95% CI 2.23-7.56; P<0.001) were identified as independent predictors of DMFS. Laterality and level showed no prognostic significance when accounting for LRN. A novel N classification scheme was derived by recursive partitioning analysis based on LRN and MLD. Compared with the 7th and 8th edition of American Joint Committee on Cancer (AJCC) systems, the new stratification exhibited better accuracy in predicting survivals. Conclusions LRN is a promising quantitative predictor of survival in NPC, eclipsing other classic LN characteristics in prognostic value. The simplified N classification scheme with LRN and MLD is predictive and practical, thus warranting further validation in future.
Highlights
Nasopharyngeal carcinoma (NPC) is one of the most common head and neck cancers in China and Southeast-Asia
More than 70% of the patients were locoregionally advanced cases, 84.7% underwent chemotherapy, and 34.5% received a cumulative cisplatin dose of over 300mg/m2, a cut-off value identified as independent predictor of survival in our previous study on 869 NPC patients receiving IMRT [15]
With a median follow-up duration of 63 months, the actuarial 5-year overall survival (OS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) were 84.4%, 85.0%, and 73.7%, respectively. 5-year DMFS was 96.4% (N0), 92.5% (N1), 86.0% (N2), 45.2% (N3a), and 57.8% (N3b), respectively according to the 7th edition of N classification and 96.4% (N0), 92.3% (N1), 81.5% (N2), and 70.3% (N3) to the 8th edition. 5-year DFS was 90.8%, 83.9%, 69.1%, 45.2%, and 45.9% according to the 7th edition and 90.8%, 83.3%, 65.4%, and 59.5% to the 8th edition. 5-year OS was 94.1%, 89.9%, Table 1: Patient characteristics
Summary
Nasopharyngeal carcinoma (NPC) is one of the most common head and neck cancers in China and Southeast-Asia. The last decade has seen significant improvements on the loco-regional control rate of NPC owing to the advances in treatment modality and techniques. Distant metastasis (DM) remains common and has become the major cause of mortality for NPC [1]. Prediction and risk stratification of distant metastasis prior to treatment are critical for therapeutic decision. The N classification in the current tumor, node, metastasis (TNM) staging systems is one of the most important predictors of DM for nondisseminated NPC. Even the latest 8th edition of N classification by American Joint Committee on Cancer (AJCC) has limitations when applied to different groups of patients. Further improvement on system robustness is still needed
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