Achieve Excellent Cancer Control Rates for Complex Tumors

Introduction: Cancer at the base of skull requires a multi-disciplinary approach for management and often requires radiation therapy to treat gross or microscopic disease that is unable to be resected and may be life threatening. Proton therapy has unique physical properties that permits the elimination of unnecessary radiation from standard radiation that results in significant toxicities such as blindness, temporal lobe necrosis, carotid artery blowout and death. The purpose of this study is to evaluate the outcomes of tumors treated at the base of skull with intensity modulated proton therapy at a single tertiary cancer center.

Methods: This study is a retrospective review of two prospective databases from 2006–2016 of patients treated at the UT MD Anderson Cancer Center to tumors located at the skull base. The analysis consists of 78 patients with a mean age of 48 years; 42% female and 58% male. Sixty four percent were never smokers and 28% had quit smoking. The median follow-up time was 0.9 years and the treatment duration was 6 weeks to a dose of 60 Gy in 30 fractions. Nineteen percent of patients had prior radiation therapy. The primary sites of the tumors were base of skull (14%), paranasal sinus (55%), and parotid (31%). The most common histology was adenoid cystic carcinoma (22%) followed by SCC (10%), SNUC (9%) and mucoepidermoid carcinoma (9%). The most common treatment was surgery followed by IMPT or surgery followed by concurrent chemoradiation with IMPT.

Results: The local, regional, and distant rates of relapse were 5%, 6%, and 6%, respectively. The rate of death was 8%. There were no acute Grade 4 or 5 toxicities; however, there was 1 Grade 4 late toxicity. Most red the 2-year actuarial rate of OS, PFS, LRFS, RRFS, and DMFS was 89%, 75%, 82%, 83%, and 86%, respectively. The most common side effects were radiation dermatitis followed by oral mucositis and nausea.

Conclusion: Intensity modulated proton therapy achieves excellent disease control rates with low rates of toxicity in combination with surgery and chemotherapy in a multi-disciplinary setting.