Abstract
Immune checkpoint inhibitors are taking on a growing role in the treatment of patients with metastatic NSCLC. Pre-clinical evidence suggests that radiotherapy may increase the frequency, or enhance the strength of the host anti-cancer immune response. We report the preliminary results of an ongoing phase I/II trial combining stereotactic body radiotherapy (SBRT) and the anti-PD-1 antibody pembrolizumab in patients with metastatic NSCLC. Eligible patients are those with metastatic NSCLC who have received no prior immune-directed therapy, and have at least 2 sites of measurable disease as per RECIST 1.1. PD-L1 expression is not required for study entry. All patients are treated with pembrolizumab at 200 mg every 3 weeks until development of progressive disease by immune-related RECIST criteria (irPD). After irPD, patients receive SBRT to a single site of disease and continue pembrolizumab. The primary endpoint is safety and tolerability. Secondary endpoints include the pre- and post-SBRT overall response rate. 27 patients with advanced NSCLC have enrolled and started trial therapy. The overall response rate (irPR and irCR) to the initial course of pembrolizumab is 35%. To date, 13 patients have had irPD: 5 were not eligible for SBRT and stopped study treatment (2 developed new brain metastases, 3 had decline in PS), and 8 patients received SBRT to a single site of disease (6 thoracic, 1 adrenal, 1 vertebral) and continued pembrolizumab. 5 of these patients are evaluable for post-SBRT response: 1 patient had confirmed irPD, 4 have irSD and continue pembrolizumab post-SBRT at a median duration of 3 months (range 1 to 5 months). 2 of the 4 patients with irSD have had > 20% decrease in the sum of diameters of their unirradiated targets, since SBRT. Regarding adverse events, in the pre-SBRT phase 6 of 27 patients (22%) developed grade 3 treatment-related toxicity (2 colitis, hepatitis, pneumonitis, hypothyroidism, conjunctivitis). In the SBRT and post-SBRT phases, there have been no grade 2 or greater treatment-related events. The addition of SBRT to pembrolizumab has not resulted in an increase in treatment-related toxicity. Several patients who had serially confirmed irPD to pembrolizumab monotherapy underwent SBRT and now have irSD, with some evidence of tumor regression. Updated results will be presented.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have