The study showed that combining pembrolizumab and SBRT is safe. In arm A, 6/9 patients experienced grade 1-2 treatment-related adverse events. In arm B, all patients experienced grade 1-2 treatment-related adverse events, and one patient experienced grade 3 treatment-related lymphopenia. They were not able to assess the efficacy based on the timing of SBRT. The overall objective response in arm A was 0% and 44% in arm B, but the trial was not powered to detect efficacy between arms.
The investigators also examined the changes in circulating tumor DNA (ctDNA). They found that treatment response was associated with a decline in ctDNA fraction compared to the baseline in patients who experienced a response. This important study establishes the safety of combining pembrolizumab and SBRT. Additional studies are ongoing to define the optimal sequence, radiation doses, and drug combination to achieve maximal anti-tumor efficacy in metastatic UC patients.
Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine
1. Sundahl N, Vandekerkhove G, Decaestecker K, Meireson A, De Visschere P, Fonteyne V, De Maeseneer D, Reynders D, Goetghebeur E, Van Dorpe J, Verbeke S, Annala M, Brochez L, Van der Eecken K, Wyatt AW, Rottey S, Ost P. Randomized Phase 1 Trial of Pembrolizumab with Sequential Versus Concomitant Stereotactic Body Radiotherapy in Metastatic Urothelial Carcinoma. Eur Urol. 2019 May;75(5):707-711. doi: 10.1016/j.eururo.2019.01.009. Epub 2019 Jan 19.
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