The 5-year survival rates were as follows: OS, 83.4%; LRFS, 93.7%; NRFS, 97.2%; and DMFS, 84.8%. A total of 38 patients (7.5%) developed locoregional recurrence, 74 patients (14.6%) developed distant metastases, and 81 patients (16.0%) died. In addition, 11 patients (2.2%) developed both locoregional recurrences and distant metastases, 18 patients (3.6%) had isolated local recurrences, 7 patients (1.4%) had isolated regional recurrences and 63 patients (12.5%) had isolated distant metastases.
The 191 patients with negative cervical lymph node involvement were divided 2 groups. Group 1 included the 110 patients without RLN metastasis, and Group 2 included the 81 patients with RLN metastasis. DMFS was significantly higher in Group 1 than Group 2 (5-year DMFS: 95.9% vs. 88.1%, P = 0.04). No significant difference was observed in the NRFS and OS of Group 1 and Group 2 (5-year NRFS: 99.1% vs. 97.4%, P = 0.38; 5-year OS: 93.8% vs. 88.0%, P = 0.14; Figure ).
Figure 1 Distant metastasis-free survival, nodal relapse-free survival and overall survival of nasopharyngeal carcinoma patients with negative cervical lymph node involvement stratified according to the absence of retropharyngeal lymph node (RLN) metastasis (Group (more ...)
In this study, 110 patients (21.7%) were staged with N0 disease according to the seven edition of the AJCC staging system. In patients with N0 disease, the 5-year OS, LRFS, NRFS and DMFS rates were 93.8%, 97.1%, 99.1% and 95.9%, respectively (Figure ). Of the N0 patients, five developed recurrence or metastasis; one of these developed local recurrence and distant metastases, one developed local and regional recurrence and then distant metastases, one developed isolated local recurrences and two developed isolated distant metastases.
Five year overall survival, local relapse-free survival and distant metastasis-free survival for patients with N0 disease according to the seventh edition of the American Joint Committee on Cancer (AJCC) nasopharyngeal carcinoma staging system.
Local recurrence in N0 disease
Of the 110 N0 patients, three developed local recurrence; one of these patients had T2N0 disease and two patients had T4N0 disease. Age (≤50 years vs. > 50 years), gender, nasal cavity extension, oropharyngeal extension, parapharyngeal space extension, skull base erosion, paranasal sinus extension, hypopharyngeal extension, orbit extension, masticator space extension, cranial nerve palsy and intracranial extension were analyzed as prognostic factors in N0 disease. Univariate analysis revealed that paranasal sinus extension, orbit extension and intracranial extension were unfavorable prognostic factors for LRFS (all P < 0.01). Multivariate analysis was performed to test the significance of the independent variables, including all of the prognostic factors in the Cox proportional hazards model, and intracranial extension was shown to be a significant independent predictor of LRFS (HR: 29.5, CI: 2.6-334.4, P < 0.01).
Distant metastasis and regional recurrence of N0 disease
Four of the 110 N0 patients developed distant metastasis; two of these patients had T1N0 disease, one had T2N0 disease and one had T4N0 disease. All of the prognostic factors were tested using univariate analysis and none were found to significantly determine DMFS.
Only one patient with T4N0 disease developed Level II lymph node recurrence, and this patient received prophylactic irradiation of the retropharyngeal area and the Level II, III, IV and V lymph node regions. At the time of lymph node recurrence, the patient was also found to have developed a local recurrence, and this patient developed distant metastases after 14 months.
Survival of N0 disease according to AJCC T-classification
In T1N0, T2N0, T3N0 and T4N0 disease, the OS rates were 97.8%, 100%, 93.8% and 76.9%, respectively; and the DSS rates were same as the OS rates. The LRFS rates were 100%, 92.9%, 100% and 88.9% and the DMFS rates were 96.6%, 90.9%, 100% and 93.3%, respectively. The OS and DSS rates were higher in T1-3 N0 patients than T4N0 patients (P < 0.01 for both). Local failure rates were significantly higher in the T4N0 subset (P = 0.01), but there were no significant difference in DMFS between T1-3 N0 and T4N0 patients (P = 0.60, Figure ). Of the 110 N0 patients, three had local failure; one of these had T2N0 disease and the other two had T4N0 with intracranial extension (Table ).
Overall survival, local relapse-free survival and distant metastasis-free survival for different T-categories, according to the seventh edition of the AJCC nasopharyngeal carcinoma staging system.
Five-year survival rates for N0 nasopharyngeal carcinoma patients according to different T-classifications of the seventh edition of AJCC staging system