Targeted agents

• EGFR inhibitors (cetuximab, erlotinib): block signaling pathways, increase radiosensitivity.

• VEGF inhibitors (bevacizumab): normalize vasculature, improve oxygenation.

Immunotherapy and RT

• Radiation can release tumor antigens, enhance immune recognition (“in situ vaccine”).

• Abscopal effect: regression of tumors outside the irradiated field, likely immune-mediated.

• Ongoing research: combining RT with immune checkpoint inhibitors (anti-PD-1, anti-CTLA-4).

Challenges

• Increased risk of immune-related toxicities.

• Optimal timing and dose-fractionation with immunotherapy still under study.