according to results from a case series.
“Effective bridging strategies may be needed to provide patients with aggressive disease access to CAR T therapy,” wrote Austin J. Sim MD, JD, of Moffitt Cancer Center in Tampa and colleagues. The findings were reported in the International Journal of Radiation Oncology, Biology, Physics.
The study included a total of 12 patients planned to receive bridging treatment with radiation prior to axicabtagene ciloleucel infusion. The cohort consisted of patients with highly aggressive disease, including six with double-hit lymphoma and six with disease 10 cm or greater in diameter.
Study participants received a radiation dose between 2 and 4 Gy per fraction to a median of 20 Gy (range, 6-36.5 Gy) and half of the participants received 20 Gy in 5 fractions or 30 Gy in 10 fractions. Of the 12 patients, 7 were administered concomitant chemotherapy.
“One patient who underwent apheresis and radiation therapy ultimately did not proceed with CAR T infusion, but was still included in our analysis,” the researchers noted.
After analysis, the researchers reported that, during bridging radiation therapy, no patients had significant toxicities or in-field disease progression of disease prior to CAR T infusion.
Post CAR T infusion, 27% of patients experienced neurotoxicity or severe cytokine release syndrome.
At 30 days, the objective response rate was 81.8%, with 27% attaining complete response. At final follow-up, the best response rate was 81.8%, with complete response achieved in 45% of patients.
The researchers acknowledged that a key limitation of the study was the retrospective design. As a result, radiation dosing was not uniform and the optimal dose and fractionation remains unclear.
In addition, Dr. Sim and colleagues advised that caution should be taken if irradiation is initiated before T-cell apheresis, and if so, blood counts should be monitored closely.
“Future investigation is warranted to optimize the use of bridging radiation before CAR T therapy,” they concluded.
No funding sources were reported. The authors reported financial affiliations with Atara Biotherapeutics, AstraZeneca, Celgene, GlaxoSmithKline, Novartis, Precision Biosciences, and several others.
SOURCE: Sim AJ et al. Int J Radiat Oncol Biol Phys. 2019 Jun 5. doi: 10.1016/j.ijrobp.2019.05.065.