Exposure to the immune system during bridging radiotherapy for Car-T cells

The objective of this study was to quantify how much dose from bridging radiotherapy is being delivered to non-lymphoma immune cells.

All patients who underwent bridging radiotherapy between January 2023 and April 2024 at the institut Curie (Paris, France) surrounding the infusion of chimeric antigen receptor (Car)-T cells, were identified. The effective dose to the immune cells was calculated for each of them.

Nine patients were included, with a mean follow-up time of 6months; one patient experienced a recurrence. No grade 2+ toxicity was reported. Median effective dose to the immune cells was 0.56Gy (range: 0.039-2.72Gy) and varied between patients. The main contribution came from the integral dose (0.43Gy, range: 0.039-1.42Gy).

The doses received by the immune system when undergoing bridging radiotherapy for Car-T cells can vary considerably from one patient to another, and the integral dose represents the primary part of this exposure of the immune system. Prospective solid data is needed in this context to evaluate the role of choice of radiotherapy techniques in bridging radiotherapy.