Simultaneous concurrent chemoradiation and SBRT in stage III NSCLC: Safety report of the phase I hybrid trial

Purpose: The phase I Hybrid trial assessed the safety of combining simultaneous stereotactic body radiotherapy (SBRT) to the primary tumor and fractionated radiotherapy to the lymph nodes with concurrent cisplatin. Materials and methods: 15 patients with stage III non-small cell lung cancer (NSCLC) with a peripheral primary tumor <5 cm were prospectively included and treated with concurrent daily low-dose chemoradiation using a hybrid fractionation schedule of simultaneous 24 fractions conventionally fractionated radiotherapy and 3 fractions SBRT. The allowed mean lung dose (MLD) was escalated by adapting the SBRT fraction dose between 14 and 18 Gy per fraction using the time‐to‐event continual reassessment method (TITE‐CRM). Results: All patients were able to be planned and treated per protocol. No dose-limiting toxicity was observed with a maximum treated MLD of 19.1 Gy. The most common Grade 1–2 toxicities consisted of radiation pneumonitis (N = 7) or rib fractures (N = 6). No G3+ pulmonary or mediastinal toxicities were observed. Although local and regional control were excellent (both 93%), 11 patients (73%) eventually developed progressive disease at distant sites at a median of 11 months. Conclusion: Simultaneous SBRT to the primary tumor and fractionated radiotherapy to the lymph nodes is feasible and safe with concurrent daily dose cisplatin with high loco-regional control rates.