S925
Clinical - Mixed sites & palliation
ESTRO 2026
Results: In the considered period, 173 pts have been treated with Hypo PT. Distribution of tumor site was reported in Fig.1. The majority (167 pts, 95%) of pts were treated in the curative setting either as exclusive or postoperative PT. Median and Mean total dose was 35 and 36 Gy RBE, respectively (range 15-69 Gy RBE). Median and mean number of fractions were 5 and 9, respectively (range 4-30) with a median and mean dose/fraction of 5 and 4,7 Gy RBE, respectively (range 2.3-8 Gy RBE). Acute toxicity data were available for 170 (98%) pts. The majority of patients (139, 82%) experienced a toxicity G < 1. Twenty-nine (17%) and 2 (1%) patients experienced a toxicity G2 and G3, respectively. Late toxicities are currently under evaluation.
approach to deliver spatially fractionated radiation therapy (SFRT) to enable targeted stereotactic body radiation therapy (SBRT) delivery to large tumors in the treatment of an Asian population. Material/Methods: We analyzed the prospectively collected data of 11 patients who received Lattice SBRT from December 2024 to June 2025 in Hong Kong. All patients have advanced malignancies with large tumors of > 6cm diameter, either refractory to, or of predicted resistance to local treatment. Five fractions Lattice SBRT delivered to 20Gy with simultaneous integrated boost to 66.7Gy on daily/alternate day basis1,2. Primary outcome was objective response, while secondary outcomes included local failure-free survival (LFFS), progression-free survival (PFS), overall survival (OS) and toxicities. Results: The median age was 64.0 years (range: 40-75 years), and 3 patients (27.3%) had an ECOG of 2. Five patients (45.5%) had metastatic diseases, 5 (45.5%) had radiotherapy-resistant tumors, 6 (54.5%) received prior systemic treatment. The most common primary tumor site was liver (27.3%), followed by sarcoma (18.2%), breast (18.2%), and colon (18.2%). Median tumor dimension was 16.6cm (IQR: 14.4-21cm). Median volume was 1372mL (IQR: 615-1974mL). Two patients had a replan and switched to conventional RT due to condition change and failed SFRT replanning. Subsequent systemic anti-cancer treatment was given in 8 patients (72.7%). Median follow-up time was 5.2 months (range: 2.1-9.0 months). Four (36.4%) patients died at the time of analysis. The 6-month LC, PFS and OS rates were 58.3% [95% confidence interval (CI): 33- 100%], 31.2% [95% CI: 10.5-92.5%] and 63.6% [95% CI: 40.7-99.5%] respectively. Pertaining to response assessment, 1 patient (9.1%) achieved complete response (CR), 8 (81.8%) achieved partial response (PR), and 1 (9.1%) had progressive disease. For patients achieving CR or PR, the median time to first response was 54 days (range 13-174 days). One patient (9.1%) was able to undergo curative resection of retroperitoneal sarcoma and subsequent clinical surveillance.Toxicity profile was favorable, with 3 patients (27.3%) experiencing manageable grade 3 toxicities (1 with pain, 1 with anemia, 1 with deranged liver transaminases) without any treatment-related deaths.
Conclusion: Hypo PT represents a feasible and safe approach for tumors located in different body sites. Patients selection remains a key factor in this clinical scenario. Larger cohorts and longer follow up are needed to confirm the presented findings. Keywords: Proton therapy, hypofractionation, toxicity
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Early Clinical Outcome of Spatially Fractionated Stereotactic Body Radiation Therapy (Lattice) in the Treatment of Bulky, Advanced Tumors Natalie SM Wong 1 , Vincent NY Chan 2 , Paul PW Kwok 1 , Jimmy HY Ngai 2 , Venus WY Lee 2 , Dennis Ngar 2 , Brian Chan 1 , Winnie WL Yip 1 , Wing Ho Mui 1 , Winnie WY Tin 1 , Ting Ying Ng 1 , Francis AS Lee 1 , Stewart Y Tung 1 , Majid M Mohiuddin 3 , Frank CS Wong 1 1 Clinical Oncology, Tuen Mun Hospital, Hong Kong, Hong Kong. 2 Medical Physics Unit, Tuen Mun Hospital, Tuen Mun, Hong Kong. 3 Radiation Oncology, Radiation Oncology Consultants, Chicago, USA Purpose/Objective: To describe the clinical outcome of patients with bulky, advanced malignancies treated with Lattice, a novel
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