2132 - Introduce the First Dynamic-CSI Technique: Enhancing Delivery Efficiency with Improved Organ at Risk Dose Sparing

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 10

Presenter(s)

Jun Liao, MD - National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, Shenzhen, Guangdong

P. Liu¹, J. F. Liao², L. Zhao³, L. Ma⁴, X. Cong¹, A. Qin⁵, X. Li¹, R. L. Deraniyagala Jr⁵, P. Chinnaiyan¹, P. Chen⁶, and X. Ding¹; ¹Department of Radiation Oncology, Corewell Health William Beaumont University Hospital, Royal Oak, MI, ²National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China., Shenzhen, China, ³Department of Radiation Medicine, MedStar Georgetown University Hospital, Washington, DC, ⁴National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China, ⁵Corewell Health William Beaumont University Hospital, Royal Oak, MI, ⁶Beaumont University Hospital Corewell Health System, Royal Oak, MI

Purpose/Objective(s): Craniospinal irradiation (CSI) is essential for the management of pediatric CNS tumors but is limited by prolonged delivery times and the risk of late toxicity. We developed Dynamic-CSI, a novel technique integrating cranial spot-scanning proton arc therapy (SPArc) with continuous couch-motion spinal irradiation, and compared its delivery efficiency and dosimetric performance with conventional multi-isocenter intensity-modulated proton therapy (IMPT).

Materials/Methods:

Five pediatric patients were retrospectively replanned with a uniform prescription of 23.4 Gy(RBE). Dynamic-CSI and conventional IMPT plans were generated with identical planning objectives and constraints. We evaluated target coverage, conformity, homogeneity, and organs-at-risk (OARs) doses using dose–volume histograms. Delivery efficiency was simulated using machine-specific models.

Results:

Dynamic-CSI demonstrated a paradigm shift in efficiency, reducing spinal delivery time by 77% (from 14.8 ± 5.9 to 3.4 ± 0.6 minutes, p < 0.05) and total craniospinal delivery time by 46% (23.6 ± 6.8 vs. 12.7 ± 0.9 minutes)

. Target coverage was equivalent, with no significant differences in CTV V107%, V100%, or D95 (p > 0.10)

. However, dose conformity was significantly improved with Dynamic-CSI (CI: 0.71 ± 0.03 vs. 0.62 ± 0.05, p = 0.014)

. Critically, Dynamic-CSI achieved substantial sensory-organ sparing. Mean cochlear dose was reduced by ~30% bilaterally (reduction of ~7 Gy[RBE], p < 0.01)

. Lens D0.03cc was reduced by >80%, dropping from ~5–6 Gy(RBE) to <1 Gy(RBE) (p < 0.01)

, shifting exposure to a significantly lower-risk category for cataracts.

Conclusion:

Dynamic-CSI markedly enhances delivery efficiency and offers critical sparing of the cochleae, eyes, and lenses without compromising target coverage. This technique represents a promising advancement for reducing late sensory toxicity and improving the treatment experience in pediatric proton CSI.