Tumor-Infiltrating Lymphocytes (TILs) as a Biomarker of Abscopal Effect of Cryoablation in Breast Cancer: A Pilot Study

Abstract

Background Morphological evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer is gaining momentum as an immunological biomarker. This experiment evaluates the role of TILs in distant tumors as a measure of abscopal effect from cryoablation of breast cancer. Methods BALB/c mice underwent bilateral orthotopic transplant with 4T1-12B (triple-negative) cells. At 2 weeks, left tumors were treated by either resection (standard of care group) or cryoablation (intervention group) followed by resection of the distant right tumors 1 week posttreatment. TIL scores were calculated from hematoxylin and eosin-stained sections and phenotyped for cytotoxic T-lymphocyte (CTL) markers by immunofluorescence. Primarily resected tumors served as baseline (Tbaseline), whereas resected distant right-sided served as the readout for abscopal effect (AbsRes or AbsCryo). Mice were monitored for tumor recurrence and metastasis. Results The AbsCryo had a significant mean (SD) increase in stromal (2.8 [1.1]%; p = 0.015) and invasive margin TILs (50 [12]%; p = 0.02) compared with TBaseline (1.0 [0]% and 31 [4.9]%, respectively). CTL phenotyping revealed a significant increase in mean (SD) CD8+ T cells (15.7 [12.1]; p = 0.02) and granzyme B (4.8 [3.6]; p = 0.048) for the AbsCryo compared with TBaseline (5.2 [4.7] and 2.4 [0.9], respectively). Posttreatment, the cryoablation group had no recurrence or metastasis, whereas the resected group showed local recurrence and lung metastasis in 40% of the mice. Postprocedure increase in TIL score of distant tumors was associated with decrease in tumor relapse (p = 0.02). Conclusions Cryoablation induced a robust tumor-specific TIL response compared with resection, suggesting an abscopal effect leading to the prevention of cancer recurrence and metastasis.

An update on the use of cryoablation and immunotherapy for breast cancer

“…Another major finding from this study was that 40% of the mice in the surgical resection group developed both tumor recurrence and metastatic disease to the lung, and when those tumors were examined, they were the only tumors in the experiment that did not demonstrate increased TILs compared to the baseline control tumor. This finding points to the importance of TILs within the tumor microenvironment and that cryoablation results in a robust antitumor response both locally and systemically, thus demonstrating the abscopal effect ( 17 ).…”

“…Tumor specific immune responses have also been described in reference to radiation therapy where a phenomenon known as the abscopal effect is seen, in which following radiation of the primary tumor there is regression of distant metastatic lesions ( 14 ). The theory behind this effect is that after radiation treatment, tumor specific antigens can be released for the immune system to recognize and use to stimulate a tumor specific response which reflects a systemic link to local response ( 17 ). This phenomenon has also been hypothesized to occur with cryoablation, given its ability to cause the release of tumor specific antigens.…”

“…Pilot studies have been performed to demonstrate this synergism and further evaluate the role cryoablation plays in the abscopal event. One preclinical study utilized a murine model of breast cancer to study TILs in distant tumors as a potential measure of the abscopal effect from cryoablation ( 17 ). In the study, two tumors were implanted at different sites into each mouse, where one tumor was targeted for local therapy (either surgical resection or cryoablation), followed by harvesting the other distant tumor one week later to study the systemic effect of the local treatment ( 17 ).…”

“…One preclinical study utilized a murine model of breast cancer to study TILs in distant tumors as a potential measure of the abscopal effect from cryoablation ( 17 ). In the study, two tumors were implanted at different sites into each mouse, where one tumor was targeted for local therapy (either surgical resection or cryoablation), followed by harvesting the other distant tumor one week later to study the systemic effect of the local treatment ( 17 ). The results of the study demonstrated increased TILs in the distant tumor with a significant increase in TILs in the cryoablation group.…”

CD8/PD-L1 immunohistochemical reactivity and gene alterations in cutaneous squamous cell carcinoma

“…Tumor metastasis was more common in cases wherein cancer did not arise in sun-exposed areas and was further related to TILs. Some biomarkers, such as PD-L1, TILs, microsatellite instability, mismatch repair, and tumor mutational burden (TMB), have been established for the prediction of immunotherapy effects in patients with metastatic disease [ 10 ]. In the current study, TIL numbers were higher in cSCC- than in cSCC+ cases, and they may suppress tumor metastasis.…”