Carcinoma of the nasopharynx treated by radiotherapy alone: determinants of distant metastasis and survival.
This retrospective study was conducted to identify the prognostic factors for distant metastasis and survival in a population of 378 patients with nasopharyngeal carcinomas treated by radiation therapy alone. All patients were treated at the University of Texas M.D. Anderson Cancer Center between 1954 and 1992, following a consistent dose and volume prescription policy. There were 286 males and 92 females. The median age was 52 years (range: 16-86 years). The majority of the patients were white Caucasians (282 patients,75%). Tumors were classified as squamous cell carcinomas (193; 51%), lymphoepitheliomas (154; 41%), or unclassified carcinomas (31, 8%). Three fourths of the patients presented with AJCC Stage IV disease (T4, N0-3, 118 patients; T1-3, N2-3 164 patients). The treatment techniques included opposed lateral fields with or without an anteroposterior or an anterior oblique pairs for dose supplementation to the primary site. Average total doses per T-stage ranged between 60.2 and 72.0 Gy. Median follow-up time was 10 years (range 0.3 to 28.6 years). A total of 103 patients (27%) developed distant metastases at a median time of 8 months (range: 1-90 months). Actuarial rates for distant metastasis were 30%, 32%, 32% at 5, 10, and 20 years, respectively. Actuarial rates for disease specific survival at the same time points were 53%, 45%, and 39% with 184 patients (49%) dying of their nasopharyngeal cancer. Advanced T-stage, N-stage, and non-lymphoepithelioma histology were independent adverse prognostic factors for disease specific survival. Advanced N-stage and low neck disease were independent adverse prognostic factors for distant metastasis with a very high rate of distant metastases for those patients who presented with both adverse factors (relative risk 7.86). On average, patients with distant metastasis lived 5 months after they were diagnosed with metastatic disease (range: 0-172 months), although four patients (4%) survived more than 5 years after diagnosis. This study demonstrates good long term survival rates after definitive radiotherapy for patients with nasopharyngeal carcinomas. Patients with advanced and lower neck disease have the highest risk of developing distant failures. Such patients can be considered the reference risk group to test the value of adjunctive chemotherapy.