NCT05578274

Abscopal Effect from Low-dose Radiotherapy in Metastatic Cancer Combined with Stereotactic Body Radiotherapy

Abscopal Effect from the Addition of Low-dose Radiotherapy in Metastatic Cancer Patients Receiving Stereotactic Body Radiotherapy: a Multicenter, Randomized Clinical Study

• Status: Not Yet Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 186 (estimated)
• Sponsor: Soonchunhyang University Hospital · Academic / Other
• Sex: All
• Age: 19 Years
• Healthy volunteers: Not accepted

Summary

Stereotactic body radiotherapy (SBRT) has been known to enhance the abscopal effect by up to 40% when delivered with immune checkpoint inhibitors (ICIs). Recently, preclinical and clinical studies demonstrate that metastatic lesions treated with non-cytotoxic low-dose radiotherapy (LDRT) significantly were reduced in the condition where SBRT and ICIs were administered together. Given that ICIs are highly expensive and some tumors are beyond the indications of ICIs, novel approaches are required to boost the abscopal effect in the absence of ICIs. Therefore, the investigators design a multicenter, randomized clinical trial that investigates the efficacy and safety of LDRT combined with SBRT in metastatic cancer patients. The primary endpoint is a lesion-specific response of LDRT lesions (i.e., abscopal effect) evaluated three months after radiotherapy. Subjects will be randomly allocated into two groups (1:1) with the stratification by planning target volume and previous use of ICIs: control group (SBRT in three fractions) or experimental group (SBRT + LDRT in three factions). Unless patients agree with randomization, subjects will participate in a prospective cohort study.

Conditions

• Neoplasms
• Secondary Malignant Neoplasm

Interventions

Type	Name	Description
RADIATION	SBRT + LDRT	SBRT is performed according to the protocol of each institution. However, the total fraction of SBRT is fixed to 3, and the treatment interval is maintained for 1-2 days. The scattered dose should not exceed EQD2 (α/β=10) 2 Gy for non-irradiated lesions. LDRT is planned to irradiate EQD2 (α/β=10) 6 Gy to lesions, considering the scattered dose caused by SBRT. If there are non-irradiated lesions, they are defined as internal control, and the total dose is limited to 0.5 Gy or less. CTV allows up to 5 mm margin for GTV, and 3-10mm for PTV margin from CTV. It is planned that the iso-dose line corresponding to the prescribed dose contains at least 90% of PTV and 95% of GTV.
RADIATION	SBRT alone	SBRT is performed according to the protocol of each institution. However, the total fraction of SBRT is fixed to 3, and the treatment interval is maintained for 1-2 days. The scattered dose should not exceed EQD2 (α/β=10) 2 Gy for non-irradiated lesions.

Timeline

• Start date: 2025-06-01
• Primary completion: 2026-01-01
• Completion: 2026-12-01
• First posted: 2022-10-13
• Last updated: 2024-12-10