Postablation Modulation after Single High-Dose Radiation Therapy Improves Tumor Control via Enhanced Immunomodulation

Area of Science:

• Oncology
• Immunology
• Radiation Oncology

Background:

• Radiotherapy (RT) typically uses equal doses per fraction for solid tumor control.
• Single high-dose radiation is emerging for tumor ablation.
• Current RT strategies lack robust immunomodulatory components.

Purpose of the Study:

• To establish a novel immunological basis for radiation dose fractionation.
• To investigate the efficacy of a single high-dose radiotherapy followed by postablation modulation (PAM) with low-dose fractions.
• To reprogram the tumor microenvironment to enhance anti-tumor immunity and tumor control.

Main Methods:

• Irradiation of 3LL and 4T1 tumors in mice using the Small-Animal Radiation Research Platform.
• Monitoring of tumor growth and survival.
• In vitro and in vivo immunomodulation analysis using flow cytometry (FACS).
• Systemic PAM-RT applied to the whole lung in a metastatic breast cancer model.

Main Results:

• Postablation modulation radiotherapy (PAM-RT) significantly delayed tumor growth and increased survival in 3LL tumor-bearing mice.
• PAM-RT enhanced immune effector cell infiltration and reduced regulatory T cells (Tregs) in tumors and lymphoid organs.
• Systemic PAM-RT in a 4T1 metastatic breast cancer model suppressed pulmonary metastases and improved survival.

Conclusions:

• A novel immunologic basis for radiation dose fractionation is presented.
• Combining ablative radiotherapy with low-dose PAM-RT enhances the immunogenic potential of RT.
• This fractionation strategy offers a promising approach for improving cancer treatment efficacy.