Trial results for pembrolizumab in combination with palliative radiotherapy for thoracic tumours were posted on ClinicalTrials.gov on 2026-04-23. The Phase 1 study established a maximum tolerated dose of 200 mg for pembrolizumab when combined with high-dose radiotherapy, with no dose-limiting toxicities observed across any treatment arm.
Background
Lung cancer is a significant health concern, being the second most common cancer in the UK with approximately 43,500 new patients diagnosed annually. A substantial proportion, about 69%, are diagnosed with advanced stage disease, where survival rates are typically less than 12 months. Immunotherapy, including drugs like pembrolizumab, has shown efficacy in treating various tumor types, including lung cancer.
Trial design
The Phase 1 study (NCT02587455) investigated pembrolizumab in combination with palliative radiotherapy for patients with thoracic tumours. The trial enrolled 24 participants and was designed to assess the toxicity rate of dose-limiting toxicities (DLTs) and determine the maximum tolerated dose (MTD) of pembrolizumab when safely combined with radiotherapy.
Key results
Key results from the trial focused on safety and dose escalation. For the outcome of 'Toxicity Rate of Dose Limiting Toxicities (DLTs) Assessed by CTCAEv4', no participants experienced DLTs across any of the evaluated groups:
- 0 Participants in the 100mg Pembro & Low Dose RT group.
- 0 Participants in the 100mg Pembro & High Dose RT group.
- 0 Participants in the 200mg Pembro & Low Dose RT group.
- 0 Participants in the 200mg Pembro & High Dose RT (MTD) group.
The 'Maximum Tolerated Dose (MTD) of Pembrolizumab That Can be Safely Combined With Radiotherapy (RT) in the Absence of Dose Limiting Toxicity (DLT) Assessed by CTCAEv4' was determined to be 200 mg for 'All Participants in the Dose Escalation Phase (Part A)'.
Regarding 'Progression Free Survival at 6 and 12 Months':
- In the 100mg Pembro & High Dose RT group, 50.0 percentage of participants showed progression-free survival at 6 months, decreasing to 25.0 percentage of participants at 12 months.
- In the 200mg Pembro & High Dose RT (MTD) group, 42.9 percentage of participants showed progression-free survival at 6 months.
- Progression-free survival data for other groups was not available.
What this means
The findings from this Phase 1 study indicate that pembrolizumab can be safely combined with palliative radiotherapy for thoracic tumours, establishing a maximum tolerated dose of 200 mg without observing dose-limiting toxicities. This favorable safety profile supports further investigation into this combination. The preliminary progression-free survival data, particularly for the high-dose radiotherapy arms, suggests potential clinical benefit that warrants evaluation in larger, later-phase trials.
Source
The information for these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT02587455, titled 'Pembrolizumab and Palliative Radiotherapy in Lung', were posted on 2026-04-23 on clinicaltrials.gov.