Abstract 22: Radiation induced and de novo squamous cell carcinoma of the temporal bone—a comparison
Authors: Tsang Raymond King-Yin , Sun Nikie 
Published: December 2017

Abstract
Introduction: Squamous cell carcinoma (SCC) temporal bone is a rare malignancy with incidence of around 1.2 per million population per year. Risk factors included chronic otitis media and chronic irritation of the skin and mucosal of the external and middle ear. A rare but important etiology is radiation to the external auditory canal from treatment of head and neck malignancies. The current study compares the presentation, treatment and prognosis of de novo temporal bone SCC and radiation induced temporal bone SCC.
Materials and Methods: From 1995 to 2016, 30 patients were treated at our institution for squamous cell carcinoma of the temporal bone, of which 16 (53.3%) occurred after prior radiotherapy for nasopharyngeal carcinoma. Comparisons were made on the stage at presentation, disease free survival and overall survival. The modified Pittsburgh staging is used for staging. Kaplan Meier plot and log rank test are used for survival analysis.
Results: All patients who had prior radiation had radiation treatment for undifferentiated carcinoma of the nasopharynx. There were 23 male and 6 female patients. One male patient who had prior radiation treatment for NPC suffered from sequential SCC of the left and right external auditory canal. Median age on presentation was 66.1 (range 46-84.5 years). There was no difference in the age of presentation between patients with de novo disease (mean 65.5 years) and radiation induced SCC (mean 65.3, p=0.97, t-test). There was also no difference in the gender distribution between de novo and radiation induced SCC of the temporal bone (p=0.63, chi-square). 27 cases were treated with surgery with 11 cases treated with radical mastoidectomy, 11 cases treated with lateral temporal bone resection and 5 cases underwent subtotal temporal bone resection. Postoperative radiotherapy was given to 14 cases. 2 patients received radiotherapy alone and 1 patient received chemo-radiation alone. The majority (85%) of the de novo cancers received postoperative radiotherapy but only 21% of the radiation-induced cancer had adjuvant radiotherapy. Radiation-induced cancer presented significantly earlier with lower T-stage (p=0.028, Mann-Whitney U test) and overall staging (p=0.019, Mann-Whitney U test).
Cumulated 5-year survival was 35%. Estimated median overall survival (OS) and disease specific survival (DSS) of the whole cohort after treatment was 43 and 48 months respectively. There was no difference in the OS and DSS between the de novo cancers and radiation-induced cancers (p=0.99 and p=0.50 respectively, log-rank test).
Conclusion: SCC of the temporal bone is a rare disease with poor prognosis despite treatment. Radiation-induced cancer of the temporal bone is a rare but important complication of radiation treatment to the head and neck region. Radiation-induced cancers presented earlier but prognosis is similar to de novo cancers. Inability to prescribe further radiation to the temporal bone after surgery may be a factor for poor prognosis in this group of patients.
Citation Format: Raymond King-Yin Tsang, Nikie Sun. Radiation induced and de novo squamous cell carcinoma of the temporal bone—a comparison [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr 22.