Trial results for atezolizumab in combination with radiotherapy for head and neck cancer were posted on ClinicalTrials.gov on 2025-07-15. The Phase 1 study, NCT04477759, investigated Dose-Escalated Hypofractionated Adaptive Radiotherapy (DEHART) with concurrent or adjuvant atezolizumab. Key safety findings indicated that 2 participants experienced dose-limiting toxicities (DLTs) in the 50 Gray (Gy) radiation therapy with concurrent atezolizumab group.
Background
Head and neck squamous cell carcinoma (HNSCC) often faces locoregional failure as the primary cause of mortality despite conventional chemoradiation therapy. This trial explored a novel approach combining adaptive radiation dose escalation, facilitated by magnetic resonance-guided radiation therapy (MRgRT), with atezolizumab. The aim was to potentially improve therapeutic outcomes while managing toxicities in patients with advanced HNSCC.
Trial design
The study, NCT04477759, was a Phase 1 trial that completed enrollment with 18 participants. It investigated the use of Dose-Escalated Hypofractionated Adaptive Radiotherapy (DEHART) with concurrent or adjuvant atezolizumab for patients with Head and Neck Neoplasm. The trial evaluated different radiation doses, specifically 50 Gray (Gy), 55 Gray (Gy), and 60 Gray (Gy), both with and without concurrent atezolizumab.
Key results
The primary safety outcome measured was the incidence of dose-limiting toxicities (DLTs) across different radiation dose levels and treatment arms. For the outcome titled "Incidence of Dose-Limiting Toxicities at 50 Gy With Concurrent Atezolizumab":
- In the group receiving 50 Gray (Gy) Radiation Therapy With Concurrent Atezolizumab, 2 Participants experienced DLTs.
- In the group receiving 50 Gray (Gy) Radiation Therapy (without concurrent atezolizumab), 0 Participants experienced DLTs.
- In the group receiving 55 Gray (Gy) Radiation Therapy (without concurrent atezolizumab), 0 Participants experienced DLTs.
- In the group receiving 60 Gray (Gy) Radiation Therapy (without concurrent atezolizumab), 0 Participants experienced DLTs.
Other measured outcomes, including "Incidence of Dose-Limiting Toxicities at 50 Gy" and "Incidence of Dose-Limiting Toxicities at 55 Gy" across various radiation therapy groups, consistently reported 0 Participants experiencing DLTs for all assessed groups.
What this means
The results from this Phase 1 trial suggest a potential safety signal when atezolizumab is administered concurrently with 50 Gray (Gy) radiation therapy for head and neck cancer, as 2 participants in this specific treatment arm experienced dose-limiting toxicities. In contrast, no DLTs were observed in radiation-only arms or at higher radiation doses without concurrent atezolizumab. These findings are crucial for informing the safety profile and dose escalation strategies for combined modality treatments involving atezolizumab and adaptive radiotherapy in this patient population.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT04477759, titled "Dose-Escalated Hypofractionated Adaptive Radiotherapy for Head and Neck Cancer," were posted on 2025-07-15 on clinicaltrials.gov.