Purpose: With improvements in breast imaging and image-guided interventions, there is interest in ablative techniques for breast cancer. Cryosurgery initiates inflammation and leaves tumor-specific antigens intact, which may induce an anti-tumor immune response. To help define the mechanisms involved in the cryoimmunologic response, we compared cryosurgery to surgery in a murine model of breast cancer.
Experimental design: BALB/c mice with MT-901 tumors underwent cryoablation or resection. Mice successfully treated were re-challenged with MT-901 or RENCA. Serum cytokine levels were analyzed by ELISA. Tumor draining lymph nodes (TDLN) and spleens were harvested, lymphocytes were activated and assessed for a specific anti-tumor response by both an interferon-gamma (IFNgamma) release assay and ELISPOT. NK cell activity was assessed by cytotoxicity against YAC-1, an NK-susceptible cell line.
Results: After re-challenge, tumors developed in 86% of mice treated by surgical excision compared to 16% of mice treated by cryosurgery (p=0.025). Cryoablation of MT-901 had no effect on re-challenge with RENCA. Cryoablation led to significantly higher levels of interleukin (IL)-12 (383.6 pg/ml +/- 32.8 versus 251.6 +/- 16.5, p=0.025) and IFN-gamma (1564 pg/ml +/- 49 versus 1244 pg/ml +/- 101, p=0.009), but no changes in IL-4 or IL-10. Tumor-specific T-cell responses were evident after cryosurgery in lymphocytes from TDLN but not from spleen. Cryoablation also increased NK activity compared to surgery (24.5% +/- 17.3 versus 16.5% +/- 5.9, p < 0.001).
Conclusion: Cryoablation results in the induction of both a tumor-specific T-cell response in the TDLN and increased systemic NK cell activity, which correlates with rejection of tumors upon re-challenge.