# Dosimetric evaluation of cone beam computed tomography-guided online adaptive radiotherapy in gastric mucosa-associated lymphoid tissue lymphoma

## TL;DR

This study shows that using cone beam CT-guided adaptive radiotherapy improves treatment accuracy and reduces organ exposure in gastric lymphoma patients.

## Contribution

The study demonstrates dosimetric benefits of CBCT-guided oART in gastric MALT lymphoma, including improved target coverage and reduced organ doses.

## Key findings

- Adaptive planning improved CTV D98% from 94.7% to 98.6% and D95% from 97.3% to 99.2%.
- OAR doses were reduced in ADP plans, including kidney V5Gy and spinal cord Dmax.
- Post-treatment dosimetric parameters remained stable, showing clinical feasibility.

## Abstract

•The dosimetric values of CBCT-guided oART for gastric MALT lymphoma were evaluated with CBCT for oART and after irradiation•CBCT-guided oART improved the target coverage, and improved dose distribution was maintained even after irradiation•CBCT-guided oART may enable the precise targeting of irradiation in gastric MALT lymphoma

The dosimetric values of CBCT-guided oART for gastric MALT lymphoma were evaluated with CBCT for oART and after irradiation

CBCT-guided oART improved the target coverage, and improved dose distribution was maintained even after irradiation

CBCT-guided oART may enable the precise targeting of irradiation in gastric MALT lymphoma

This study evaluated dosimetric values of cone beam computed tomography (CBCT)-guided online adaptive radiotherapy (oART) in patients with gastric mucosa-associated lymphoid tissue (MALT) lymphoma, accounting for interfractional and intrafractional motion.

Four patients with stage I gastric MALT lymphoma received CBCT-guided oART. For each of the 60 treatment sessions, scheduled (SCH) and adapted (ADP) plans were generated. Dosimetric evaluation focused on clinical target volume (CTV) and organs at risk (OARs). Metrics included CTV D98 % and D95 %, mean dose to the liver and left and right kidneys, maximum dose to the spinal cord, and V5Gy for bilateral kidneys. Adaptive planning CBCT-based contours were propagated to synthetic CTs of SCH and ADP plans to assess interfractional motion. Post-treatment CBCT-based contours were propagated to synthetic CTs of the ADP plan to evaluate intrafractional motion.

ADP plans significantly improved CTV coverage: mean D98% increased from 94.7 % in the SCH plan to 98.6 %, and D95% from 97.3 % to 99.2 % (p < 0.001). Most OAR doses were reduced in the ADP plans, including bilateral kidney V5Gy (11.3 % vs. 8.3 %, p < 0.001) and spinal cord Dmax (9.8 Gy vs. 7.9 Gy, p < 0.001). Liver Dmean was slightly higher in the ADP plan (11.4 Gy vs. 11.1 Gy, p = 0.002). No significant differences were observed in CTV and OAR dosimetric parameters between adaptive planning and post-treatment CBCTs (e.g., CTV D98%: 98.6 % vs. 98.5 %, p = 0.629).

CBCT-guided oART improved target coverage and maintained post-treatment dosimetric stability in gastric MALT lymphoma, supporting clinical feasibility.