A Pilot Trial of Proton-Based Cardiac Sparing Accelerated Fractionated Radiation Therapy in Unresectable Non-small Cell Lung Cancer With Extended Durvalumab Therapy (PARTICLE-D)

Abstract

Purpose: Concurrent chemoradiotherapy is the current non-surgical standard of care for locally advanced non-small cell lung cancer (NSCLC). However, this is a difficult regimen to tolerate especially for those who are elderly, have multiple comorbidities or poor performance status. Alternative treatment regimens are needed for this vulnerable population. We report initial results of concurrent durvalumab, an immune checkpoint inhibitor, and hypofractionated, dose-escalating, proton external beam radiotherapy (EBRT).Patients and Methods: This phase I, pilot dose-escalation trial enrolled seven patients with newly diagnosed stage IIIA-IIIC NSCLC who were unable or unwilling to undergo concurrent chemoradiotherapy. Patients previously treated with immunotherapy were excluded. Five patients in the initial phase of this 3+3 study design received a fixed dose of durvalumab each 28-day cycle plus hypofractionated proton EBRT 60 Gy in 20 fractions while two patients received the escalation dose of 69 Gy in 23 fractions. The primary objective assessed safety while secondary objectives assessed feasibility and adverse events.Results: All patients experienced treatment-related adverse events, primarily grades 1-2. Pneumonitis and anemia were the most common. Only one dose limiting toxicity occurred, in arm one, which was a grade 3 pneumonitis leading to grade 5 pneumonia. Additionally, two delayed-onset grade 5 tracheal necrosis events occurred > 13 months after treatment initiation.Conclusions: Concurrent durvalumab plus hypofractionated proton EBRT was well tolerated in the short term. However, three treatment-related deaths, including two delayed-onset grade 5 tracheal necroses negatively impacted overall safety. A dose de-escalation protocol of proton-based radiotherapy plus durvalumab is warranted.