Long-term outcome and prognostic factors of nasopharyngeal carcinoma treated by intensity modulated radiotherapy

Objective: To study long-term outcome and prognostic factors of nasopharyngeal carcinoma treated by intensity modulated radiotherapy. Methods: A total of 299 patients with non-disseminated nasopharyngeal carcinoma who received initial radiotherapy were analyzed retrospectively. The primary lesion and the upper neck received 70 Gy (5 fraction per week in all 30 fraction) by intensity-modulated radiotherapy (IMRT). The lower neck and the supraclavicular fossa was given 54 Gy (5 fraction per week in all 30 fraction) by a single anterior tangent field with spinal cord block. A median dose of 9.2 Gy (4-20 Gy) was given to the residual primary lesion by IMRT or X-knife. The Kaplan-Meier method was used for calculating the overall survival (OS), disease progression-free survival (DPFS), distant metastasis-free survival (DMFS), Log-rank test was used for evaluating the differences between groups. Multivariate prognostic factor was analyzed by Cox method. Results: The follow-up rate was 99.7%. 119 patients were followed-up more than with 5 years. The 5-year OS for stage I + II, stage M and stage IV were 97.1%, 82.7% and 52.2% (χ² = 46.19, P = 0.000), the 5 years DPFS were 100%, 77.6% and 57.1% (χ² = 23.29, P = 0.000), DMFS were 100%, 82.3%, 63.7% (χ² = 16.57, F = 0.000) respectively. The 5 year OS, DPFS and DMFS of male and female were 70.7% vs 94.1% (χ² = 16.82, P = 0.000), 71.5% vs 87.3% (χ² =4.74, P = 0.029) and 77.2% vs 89.7% (χ² = 4.38, P = 0.036) respectively. For patients who were younger than 45-years, the male had a significantly unfavorable 5-year OS (66.8% vs. 91.2%, χ² =7.07, P = 0.008), DPFS (59.9% vs. 91.2%, χ² = 7.72, P = 0.005) and DMFS (66.4% vs. 94.0%, χ² =8.46, P = 0.004); For patients who were old than 45-years, only OS was significantly different between male and female (72.2% vs. 96.0%, χ² = 10.19, P = 0.001). Multivariate analysis showed the independent prognostic factors for OS, DPFS, DMFS, were gender(χ² = 14.27, 5.72, 17.64, P = 0.000, 0.017, 0.000), TNM stage (χ² = 5.33, 15.70, 10.57, P = 0.021, 0.000, 0.001) and lymph nodes capsular invasion (-4.30, 11.08, 21.24, P = 0.038, 0.001, 0.000). Intracranial invasion and supraclavicular lymph node metastasis were independent, prognostic factors for OS ( χ² = 13.32, 5.38, F = 0.000, 0.020). Conclusions: The TNM stage, lymph nodes capsular invasion and gender are independent prognostic factors for nasopharyngeal carcinoma treated by intensity-modulated radiotherapy. The patients of younger than 45-years own a worse outcome. (authors)