Objectives: The aim of this study was to determine the impact of the involvement of the superior pharyngeal constrictor muscle (SPCM) evaluated by magnetic resonance imaging (MRI) on outcome in oropharyngeal squamous cell carcinomas (OPSCCs). Methods: A retrospective study including consecutive patients with OPSCC treated with curative intent. Results: A total of 82 consecutive patients with OPSCC met inclusion criteria. At multivariate analysis, patients with SPCM infiltration were at significantly higher risk of death (HR: 3.37, CI: 1.21-9.38) and progression (HR: 3.39, CI: 1.38-8.32). In a multivariate model conditioned on HPV status, a significantly higher risk of death and progression was observed by combining both SPCM and HPV status with patients harboring an HPV-negative OPSCC with SPCM infiltration showing the poorest outcome. Conclusion: MRI evidence of SPCM involvement significantly and independently increases the risk of death and progression in subjects with OPSCC. Considering both MRI-assessed SPCM infiltration and HPV status significantly improved risk stratification in these malignancies.
