3564 - Early Clinical Results of Spatially Fractionated Radiation Therapy (SFRT) with GRID in the Treatment of Bulky/Advanced Tumors

02:30pm - 03:45pm PT

Hall F

Screen: 26

POSTER

Presenter(s)

Natalie Wong, MBBS, MRes(Med), FRCR - Tuen Mun Hospital, Hong Kong, Hong Kong

N. S. M. Wong¹, P. W. Kwok¹, V. N. Y. Chan², H. Y. Ngai², V. W. Y. Lee², D. Ngar², J. S. Nyaw¹, W. W. Y. Tin¹, T. Y. Ng¹, F. A. Lee¹, S. Y. Tung¹, M. M. Mohiuddin³, and C. S. F. Wong¹; ¹Department of Clinical Oncology, Tuen Mun Hospital, Tuen Mun, Hong Kong, ²Medical Physics Unit, Tuen Mun Hospital, Tuen Mun, Hong Kong, ³Radiation Oncology Consultants, Chicago, IL

Purpose/Objective(s):

To describe the clinical outcome of patients with bulky/advanced malignancies treated with the spatially fractionated radiotherapy (SFRT) protocol in an Asian population.

Materials/Methods:

We analyzed the prospectively collected data of 19 patients who received palliative SFRT from January 2024 to December 2024 in Hong Kong. All patients have advanced malignancies with large tumors of > 7cm diameter, either refractory to, or of predicted resistance to local treatment. A single fraction (fr) of 15-18Gy of SFRT was delivered with GRID. Primary outcome was objective response, while secondary outcomes included progression-free survival (PFS), overall survival (OS) and toxicities.

Results:

The median age was 61.8 years (range: 49-88 years), and 4 patients (21.1%) had an ECOG of 2. Nine patients (47.3%) had metastatic diseases, 12 (63.1%) had radiotherapy-resistant tumors, 13 (68.4%) received prior systemic treatment. The most common primary tumor site was head and neck (42.1%), followed by sarcoma (21.1%), breast (21.1%), and liver (15.8%).

Median tumor dimension was 13.5cm (IQR: 9.9-20.1cm]. Median volume was 496mL (IQR: 103-1966mL). The median dose was at 15Gy (range 15-18Gy). SFRT was followed by conventional RT in 17 patients (89%), with a median EQD2 of 36Gy (17.6-64.8Gy). Subsequent systemic anti-cancer treatment was given in 6 patients (31.1%).

The median follow-up time was 3.1 months (range: 0.6-12.3 months). Twelve (63%) patients died at the time of analysis. Of the 7 surviving patients, median follow-up was 4.0 months (range: 1.6 -12.4 months). Median progression free survival was 2.5 months (CI: 1.8-3.2 months). Median overall survival of the entire cohort was 3.8months (CI 2.5-5.1 months).

Response assessment was evaluable in 17 (89.4%) patients, of which 1 patient (5.9%) achieved complete response (CR), 9 (52.9%) achieved partial response (PR), and 3 (17.6%) had static disease, 3 (17.6%) had progressive disease. For patients achieving CR or PR, the median time to first response was 25.0 days (range 11-58 days). There were no treatment related deaths or = grade 3 toxicities.

Conclusion:

SFRT with GRID of 15-18Gy single fr provides rapid and promising tumor response with minimal toxicities in patients with advanced, refractory diseases, fair performance statuses, and/or limited treatment alternatives. Future multi-center, prospective, validation studies are warranted to standardize treatment algorithms and optimize patient management.