# Feasibility of Utilizing Spot-Scanning Proton Arc (SPArc) for Whole-Lung Irradiation: A Case Report

## TL;DR

This case report explores a new proton therapy technique for lung cancer treatment that better protects the heart and reduces overall body dose.

## Contribution

The study introduces and evaluates the feasibility of Spot-scanning Proton Arc (SPArc) therapy for whole-lung irradiation in a pediatric patient.

## Key findings

- SPArc reduced mean heart dose to 5.41 Gy compared to 8.48 Gy with IMPT and 9.56 Gy with VMAT.
- SPArc had a lower integral body dose (98 Gy·L) compared to VMAT (137 Gy·L) and IMPT (189 Gy·L).
- SPArc demonstrated improved delivery efficiency compared to IMPT and VMAT.

## Abstract

Photon radiotherapy is the conventional method in the treatment of bilateral whole-lung metastasis. However, uncertainties, longer delivery times, large lateral penumbra, and motion interplay limit intensity-modulated proton therapy (IMPT)’s use in bilateral lung metastases. To overcome such limitations in IMPT, this study explores the feasibility of using a novel proton therapy technique, Spot-scanning Proton Arc (SPArc) therapy, to improve the dose sparing to the heart and other healthy tissue for this pediatric patient compared to the volumetric modulated arc therapy (VMAT) and IMPT.

A 13-year-old patient with a malignant neoplasm of bone and articular cartilage, presenting with bilateral whole-lung metastasis, received whole-lung irradiation of 15 Gy in 10 fractions using VMAT. For comparative analysis, plans were generated using IMPT and SPArc.

The study showed that SPArc was superior in sparing the heart and enhancing delivery efficiency compared to both VMAT and IMPT. The mean heart dose was 5.41 Gy for SPArc, 8.48 Gy for IMPT, and 9.56 Gy for VMAT. D50 of the heart was 3.06 Gy for SPArc, 9.13 Gy for IMPT, and 9.12 Gy for VMAT. The integral body dose was 137 Gy·L in VMAT,189 Gy·L in IMPT, and 98 Gy·L in SPArc.

Spot-scanning proton arc demonstrated effective heart sparing and lower body-integral dose for whole-lung irradiation. Delivery simulations suggested improved efficiency compared with IMPT.