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

PURPOSE: 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.

PATIENTS AND

METHODS

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.

RESULTS

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.

CONCLUSION

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.