Prognostic factors in 677 patients in Singapore with nondisseminated nasopharyngeal carcinoma

Abstract

Background: The objective of the current study was to describe the survival of nasopharyngeal carcinoma (NPC) patients in Singapore, verify the prognostic value of the revised 1997 TNM staging system, and develop a multivariate prognostic model for NPC. In addition, the authors also examined the prognostic value of characteristics of lymph node spread and parapharyngeal involvement.

Methods: A prospectively maintained database containing clinical and computed tomography scan data was used to reclassify 677 NPC patients treated between 1992 and 1994 according to the new staging system. Records were linked with the death registry to ascertain the patient's vital status and date of death. Overall and stage specific survival were analyzed using the Kaplan-Meier method and the log rank test. Univariate and multivariate Cox proportional hazards regression analysis were used to obtain prognostic models.

Results: Two hundred seventy-four deaths (40.5%) occurred. The 5-year survival rate was 56.6% (95% confidence interval [95% CI], 52.3%, 60.7%). The stage specific 5-year survival rates were: Stage I, 88%; Stage IIA, 75%; Stage IIB, 74%; Stage III, 60%; Stage IVA, 35%; and Stage IVB, 28%. TNM stage was found to be a statistically significant prognostic factor (P < 0.0001). Cranial nerve (hazard ratio [HR]: 2.77), orbit (HR: 5.71), and intracranial involvement (HR: 2.46) conferred a particularly bad prognosis in univariate analysis. Independently significant prognostic factors were age; lymph node status; and paraoropharyngeal, cranial nerve, orbit, and nasal involvement. Among lymph node positive patients, independently significant prognostic lymph node characteristics were Ho level and laterality. Although parapharyngeal involvement appeared to be prognostically unimportant, paraoropharyngeal involvement distinguished a subgroup with a poorer prognosis (HR: 1.84; 95% CI, 1.45, 2.34; P < 0.0001). Lateral spread to the medial infratemporal fossa and beyond also was found to confer a poorer prognosis.

Conclusions: The results of the current study show that the revised 1997 TNM staging system is prognostically useful. Subdivision into paraoropharyngeal involvement and using the medial infratemporal fossa to delineate prognostically significant lateral spread should be considered in future revisions.