Posted: Thursday, October 19, 2023
With “better-than-expected” secondary outcomes, results of a prospective phase II study indicated that combination therapy of single-fraction, low-dose (8 Gy) radiation with the PD-1 inhibitor pembrolizumab in patients with stage I to III relapsed or refractory multiple myeloma are worth assessing in future trials, according to its investigators. Currently, radiotherapy’s role in this scenario is mainly for palliation, and PD-1 inhibitors had previously failed to show efficacy in such patients as well, noted Mohammad Khan, MD, PhD, of Emory University, Atlanta, and colleagues at the 2023 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 314).
With a primary outcome of toxicity, but also to see whether the combination could provide early signals of safety and response, the trial enrolled 25 adults (mean age, 60 years; mean number of previous failed treatments, 5.2) with an Eastern Cooperative Oncology Group status of 0 to 1 and measurable and/or progressive disease. They also needed to be candidates for pembrolizumab and to have an osseous and/or extraosseous lesion that could be radiated.
The primary endpoint of acceptable toxicity was met, with no grade 2 or higher radiation-related toxicity within the irradiated volume. One case of grade 3 or higher pembrolizumab-related toxicity was reported. What’s more, abscopal response was seen in 5 of the 25 patients, stated Dr. Khan and co-investigators, with several showing “robust reductions in paraproteins and other myeloma [laboratory markers].”
After initial radiotherapy, patients received 200 mg/kg of pembrolizumab intravenously about every 3 weeks for at least 2 years or until disease progression. After enrollment between 2018 and 2021, patients were assessed at 3 months, 6 months, and 12 months; those with stable disease or better continued the trial.
Disclosure: For Dr. Khan’s complete disclosure information, visit astro2023.eventscribe.net.