Pretreatment prognostic factors of survival and late toxicities for patients with nasopharyngeal carcinoma treated by simultaneous integrated boost intensity-modulated radiotherapy

Background: To scrutinize the pretreatment prognosticators on survival and late toxicities in a homogenous cohort of nasopharyngeal carcinoma (NPC) patients treated by simultaneous integrated boost intensity-modulated radiation therapy (SIB-IMRT). Methods: A total of 219 non-distant metastatic NPC patients consecutively treated by SIB-IMRT at a single institute were collected. The pretreatment factors including the socio-demographic variables, TNM stages, gross tumor volume (GTV), Epstein-Barr virus (EBV)-DNA, and hematologic inflammatory markers were analyzed. Cox model was used to screen the prognostic factors of late toxicities and four survival outcomes including locoregional relapse-free survival (LRRFS), distant metastasis-free survival (DMFS), failure-free survival (FFS), and overall survival (OS). Results: Statistically significant inter-correlations were observed between the values of EBV-DNA, some hematologic inflammatory markers, GTV, and N classification. The 5-year LRRFS, DMFS, FFS, and OS rates were 87.9%, 89.4%, 79.4%, and 81.3%, respectively. Multivariate analysis revealed that advanced N classification (N2-3 vs. N0-1) remained the only significant negative prognosticator for all the four survival outcomes. An increased monocyte percentage and a decreased lymphocyte-to-monocyte ratio were significantly associated with poorer FFS and OS, respectively. Larger GTV was observed to be predictive of poorer LRRFS. Patients with T3-4 (HR: 3.5, 95% CI: 1.0-12.1, p=0.048) or higher GTV (HR: 1.006, 95% CI: 1.001-1.011, p=0.027) were associated with higher incidence of radiation neuropathy. Conclusion: N classification remains the most significant survival predictor for NPC patients treated by SIB-IMRT after adjusting these biomarkers. GTV impacts not only on locoregional control but also radiation neuropathy.