Radiotherapy and Immunotherapy for Cancer: From "Systemic" to "Multisite"

Area of Science:

• Oncology
• Immunology
• Radiation Oncology

Background:

• Cancer immunotherapy combines radiation therapy with immune-stimulating drugs.
• The abscopal effect, where radiation of one tumor impacts distant tumors, is observed but infrequent in clinical trials.
• Preclinical data suggest T cells surviving radiation contribute to therapeutic effects.

Purpose of the Study:

• To explore reasons for discrepancies between preclinical and clinical abscopal effects.
• To propose strategies for enhancing radio-immunotherapy efficacy.

Main Methods:

• Review of preclinical and clinical data on radio-immunotherapy and the abscopal effect.
• Discussion of potential mechanisms for the abscopal effect, including T cell involvement.
• Analysis of clinical trial outcomes and preclinical findings.

Main Results:

• The abscopal effect is potentiated by immunostimulatory drugs but remains infrequent in current clinical trials.
• Preexistent intratumoral T cells may survive radiation and play a role in its therapeutic impact.
• Discrepancies exist between preclinical observations and clinical outcomes of radio-immunotherapy.

Conclusions:

• The infrequent success of the abscopal effect in clinical trials may stem from underlying biological mechanisms.
• Irradiating multiple or all tumor sites alongside systemic immunotherapy could potentially increase radio-immunotherapy efficacy.
• Further research is needed to optimize combination strategies for improved cancer treatment outcomes.