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

Abstract

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.

Keywords: Epstein-Barr virus DNA; Gross tumor volume; Hematologic inflammatory marker; Nasopharyngeal carcinoma; Simultaneous integrated boost intensity-modulated radiation therapy.

Fig. 1

Survival comparisons of NPC patients by different pretreatment biomarkers based on the cutoff point through ROC curve analysis: (a) Failure-free survival for those with monocyte percentage < 7.2% vs. ≥ 7.2%; (b) Overall survival for those with L/M ratio ≥ 4.3 vs. < 4.3; (c) Locoregional relapse-free survival for those with gross tumor volume < 67.5 ml vs. ≥ 67.5 ml

Fig. 2

Cumulative incidence rate of radiation neuropathy for those with gross tumor volume < 64.5 ml vs. ≥ 64.5 ml