Abstract P2-20-07: Immunotherapy becomes a treatment option in cryoablated Luminal A breast cancers

Abstract Background: Most breast cancers are not inherently immunogenic, and as a result are difficult to treat with immunotherapy. However, recent research has shown that triple-negative breast cancer (TNBC) and HER-2 positive (HER2) breast cancers can stimulate some level of an immune response. In contrast, the most common form of breast cancer, the luminal A (hormone receptor-positive (HR+)/HER-2 negative), has shown low involvement of tumor-infiltrating lymphocytes (TILs) and low expression of immune checkpoint inhibitors specifically programmed death-ligand-1 (PD-L1). Cryoablation, the destruction of cells using ultra-low temperatures, has been used as a primary treatment method for benign breast tumors and is in clinical trials to evaluate its use for invasive breast cancer. A secondary effect of cryoablation is the release of cellular proteins that can function as neoantigens and are in their native folded state We hypothesize that release of these native neoantigens might trigger an immune response capable of preventing/reducing metastasis and local relapse. In this pilot study, we evaluated biopsy material, cryoablated specimens and sentinel lymph nodes (SLN) from patients enrolled in the ACOSOG Z1072 trial at Lankenau Medical Center (LMC) [N=18] with cancers < 2 cm. Responses were compared to patients treated with surgical resection. Methods: After obtaining IRB approval for retrospective analyses of specimens from the ACOSOG Z1072 trial, these samples were evaluated with immunohistochemistry (IHC) using commercially available antibodies and standard techniques to determine changes in CD4, CD8, CD20, CD21, CD1c levels, as well as the immune checkpoint regulators PD-1, PD-L1 and CTLA-4, and the immune modulator IDO1. Patient samples included biopsy, surgical material, and SLN collected from the patients and were compared with patients of similar age, tumor characteristics and time to surgery. Per the ACOSOG trial protocol, tumors had to be surgically removed within 28 days of cryoablation, but the exact time was left to the surgeon’s discretion. Participating surgeons at LMC preferred to remove tumors on average 24.7 days after ablation resulting in an average time from diagnosis to surgical removal of 43.3 days. Results: Cryoablation of the tumors resulted in coagulative necrosis presenting as a gelatinous mass surrounded by a fibrous capsule. The ACOSOG trial demonstrated effective cryoablation-induced destruction of ER+ invasive ductal carcinoma lesions in 92% of patients (N=86). On IHC staining of the cryoablated samples, more CD8+ lymphocytes were identified compared to CD4+, which was consistent with pattern among non-cryoablated tumors, albeit to a lesser degree. Though no difference in percentage of PD-1 positive cells were observed between treatment modalities, positive cells in cryoablated tumors had mostly moderate-to-strong staining. We observed a 20% increase in cells positive for PD-L1 after cryoablation with predominantly strong staining. Though IDO1 had fewer positive cells in the tumor mass, the expression in SLN was higher with nearly all cells exhibiting strong staining. Compared to the patients who were treated with surgery alone, the SLNs of cryo patients had higher levels of CD20+ B cells as well as CD21+ follicular dendritic cells. CTLA-4 was seen sporadically, but with a slight preference for the surgery patients. Conclusion: We show that cryoablation of breast cancer lesions in vivo can induce an immune response in HR+ tumors, turning an immunogenically cold tumor into an immunogenically hot, tumor potentially responsive to check-point inhibitors and immune modulators. Possibly providing less toxic treatment options for elderly patients and/or patients with comorbidities All local cryo patients in the clinical trial are currently disease-free (F/U 5 - 13years), while 1 surgical patient is alive with late recurrence (11 years post-surgery). Citation Format: Zachary Aukers, Jonah Klein, Vincent Ciocca, Vlasta Zemba-Palko, Jennifer Sabol, Robin Ciocca, Laura Mandik-Nayak, Ned Carp, Margaretha Wallon. Immunotherapy becomes a treatment option in cryoablated Luminal A breast cancers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-07.