Anti-Tumor Immunization Efficacy after Particle-Radiation Exposure.

Particle radiotherapy is successful in treating cancers that are typically refractory to conventional low-LET therapy; however, the underlying molecular mechanisms remain largely unknown. Some suggest that, in addition to local tumor control, particle radiotherapy may induce long-range systemic anti-cancer effects involving the immune system that may be responsible for the overall success of the modality. Using previously published methodology, we have assessed anti-tumor responses in vivo using an immunization model. Comparing the efficacy of tumor cells killed by X rays and high-LET ions to protect against subsequent tumor challenge in mice, we have observed that at equidoses, heavy ions are more effective at generating anti-tumor responses than X rays.