Prognostic significance of maximum primary tumor diameter in nasopharyngeal carcinoma

Background: To evaluate the prognostic value of maximum primary tumor diameter (MPTD) in nasopharyngeal carcinoma (NPC). Methods: Three hundred and thirty-three consecutive, newly-diagnosed NPC patients were retrospectively reviewed. Kaplan-Meier analysis and the log-rank test were used to estimate overall survival (OS), failure-free survival (FFS), distant metastasis-free survival (DMFS) and local relapse-free survival (LRFS). Cox proportional hazards regression analysis was used to assess the prognostic value of MPTD. Results: Median follow-up was 66 months (range, 2-82 months). Median MPTD in stage T1, T2, T3 and T4 was 27.9, 37.5, 45.0 and 61.3 mm, respectively. The proportion of T1 patients with a MPTD <= 30 mm was 62.3%; 72% and 62.9% of T2 and T3 patients had a MPTD > 30-50 mm, and 83.5% of T4 patients had a MPTD > 50 mm. For patients with a MPTD <= 30 mm, > 30-50 mm and > 50 mm, the 5-year OS, FFS, DMFS and LRFS rates were 85.2%, 74.2% and 56.3% (P < 0.001); 87%, 80.7% and 62.8% (P < 0.001); 88.7%, 86.4% and 72.5% (P = 0.003); and 98.2%, 93.2% and 86.3% (P = 0.012), respectively. In multivariate analysis, MPTD was a prognostic factor for OS, FFS and DMFS, and the only independent prognostic factor for LRFS. For T3-T4 patients with a MPTD <= 50 mm and > 50 mm, the 5-year OS, FFS and DMFS rates were 70.4% vs. 58.4% (P = 0.010), 77.5% vs. 65.2% (P = 0.013) and 83.6% vs. 73.6% (P = 0.047), respectively. In patients with a MPTD <= 30 mm, 5-year LRFS in T1, T2, T3 and T4 was 100%, 100%, 88.9% and 100% (P = 0.172). Conclusions: Our data suggest that MPTD is an independent prognostic factor in NPC, and incorporation of MPTD might lead to a further refinement of T staging.