Impact of Expression of CD44, a Cancer Stem Cell Marker, on the Treatment Outcomes of Intensity Modulated Radiation Therapy in Patients With Oropharyngeal Squamous Cell Carcinoma

Abstract

To investigate the significance of CD44 protein expression on the treatment outcomes of radiation therapy in patients with oropharyngeal squamous cell carcinoma (OPSCC) with or without p16 protein expression in the tumor tissue. We reviewed the medical records of 58 OPSCC patients who had undergone radiation therapy and examined the tumor tissue expressions of CD44 and p16 protein by immunohistochemical staining. The correlations between the expressions of these proteins and the patients' treatment outcomes were analyzed. The data of 58 consecutive OPSCC patients who had undergone definitive intensity modulated radiation therapy were analyzed. The male/female ratio was 55:3, and the median age was 64 years. The clinical stage of the disease was stage II in 7 patients, stage III in 5 patients, stage IVA in 35 patients, and stage IVB in 11 patients. Of the patients, 79% received additional induction and/or concurrent chemotherapy. The median follow-up duration was 34 months. The 3-year overall survival, progression-free survival (PFS) and locoregional control (LRC) rates of all the patients, regardless of the results of immunohistochemistry, were 73%, 64% and 76%, respectively. The PFS and LRC rates in the CD44(-) patients (86% and 93%, respectively) were significantly higher than those in the CD44(+) patients (57% and 70%, respectively). The PFS and LRC rates in the p16(+) patients (83% and 90%, respectively) were significantly higher than those in the p16(-) patients (45% and 61%, respectively). Patients who were CD44(-)/p16(+) showed the best LRC rates, and those who were CD44(+)/p16(-) showed the worst PFS and LRC rates among all the groups. Profiling of CD44 and p16 protein expressions by immunohistochemical staining is useful for predicting the treatment outcomes in patients with OPSCC undergoing definitive intensity modulated radiation therapy.