Background: Volumetric tumor staging has been shown as superior prognostic tool compared to the conventional TNM system in patients undergoing definitive intensity-modulated radiotherapy (IMRT) for head and neck cancer. Recently, clinical immunoscores such as the neutrophil-lymphocyte ratio (NLR) have been investigated as prognostic markers in several tumor entities. The aim of this study was to assess the combined prognostic value of NLR and tumor volume in patients treated with IMRT for oropharyngeal cancer (OC).
Methods: Data on all consecutive patients treated for locally advanced or inoperable OC with IMRT from 2002-2011 was prospectively collected. Tumor volume was assessed based on the total gross tumor volume (tGTV) calculated by the treatment planning system volume algorithm. The NLR was collected by a retrospective analysis of differential blood count before initiation of therapy.
Results: Overall, 187 eligible patients were treated with a median IMRT dose of 69.6 Gy. Three-year recurrence-free survival (RFS) for low, intermediate, high and very high tumor volume groups was 88%, 74%, 62% and 25%, respectively (p = 0.007). Patients with elevated NLR (>4.68) showed a significantly decreased 3-year RFS of 44% vs. 81% (p < 0.001) and 3-year OS of 56% vs. 84% (p < 0.001). The NLR remained a significant prognostic factor for RFS and OS when tested among tumor volume groups. Univariate and multivariate regression analysis confirmed both tumor volume and NLR as independent prognostic factors. The NLR offered further statistically significant prognostic differentiation of the small/intermediate/large tumor volume groups.
Conclusion: The NLR remains an independent prognostic factor for patients with OC undergoing radiotherapy independent of the tumor volume.
Keywords: Head and neck cancer; IMRT; NLR; Neutrophil-lymphocyte ratio; Oropharyngeal cancer; Radiotherapy; Volumetric staging.