Stereotactic Body Radiation Therapy for the First-Line Comprehensive Treatment of Oligometastatic Nasopharyngeal Carcinoma: A Prospective, Single-Arm, Phase II Trial

Abstract

The current treatment strategy for patients with metastatic nasopharyngeal carcinoma (NPC) is mainly based on palliative chemotherapy, with low complete remission rate and poor progression-free survival (PFS). Radiation therapy has proven efficacy in the treatment of patients with nonmetastatic NPC, with emerging indication in the setting of limited metastatic disease. We proposed a single-arm phase II study to determine if metastasis-directed SBRT plus systemic treatment could prolong PFS compared with historical findings at first-line therapy for patients with oligometastatic NPC.We enrolled metastatic NPC with 1-5 metastatic lesions, with all metastases amenable to SBRT. Prescribed doses ranged from 25-50 Gy administered in five fractions. All patients received systemic chemotherapy before or after SBRT. The primary endpoint was PFS at 1 year from the start of SBRT treatment.Between October 2016 and January 2020, 24 patients with a median age of 48 years (range, 29-65 years) were recruited. A total of 44 sites were treated with 11 of 24 patients receiving SBRT to more than one site. Spinal bone was most often irradiated. By Kaplan-Meier actuarial analysis, 1-year PFS was 62% and overall survival rate 87%. Most patients progressed in new distant sites with only one local SBRT failures out of 44 lesions. Patients with lung metastasis had a lower chance of distant progression than those with bone metastasis or liver metastasis. There were no SBRT relevant grade 3-5 toxicity, and only one patient suffered from grade 2 adverse event.Use of metastasis-directed SBRT with systemic chemotherapy for patients with oligometastatic NPC as first-line therapy was well tolerated, and resulted in high PFS, substantially greater than historical values for patients who only received systemic agents.