Preoperative Pembrolizumab Treatment Changes Tils in Naïve Stage I/IIA TNBC Patients Within a Window of Opportunity Trial

Abstract

High levels of stromal tumor–infiltrating lymphocytes (sTILs) are significantly associated with chemosensitivity and improved overall survival for patients with triple negative breast cancer (TNBC). Our aim is to determine if we can significantly increase sTILs from biopsy to lumpectomy in a presurgical window of opportunity trial with pembrolizumab (pembro) and intraoperative radiation (IORT) in treatment-naïve early stage TNBC compared to matched IORT only controls. The hypothesis is that preoperative pembro treatment in TNBC patients will increase the density and change the spatial distribution of TILs from biopsy to lumpectomy. Seven women with node negative TNBC <2.5 cm were enrolled in either our presurgical trial with pembro and IORT as an upfront boost (NCT02977468) or a parallel study with IORT alone (NCT03165487). The treatment consisted of two doses of pre-operative pembro (200mg IV) given alone with the second dose -10 to -18 days from surgery; 20Gy IORT was delivered during surgery to the lumpectomy bed. All patients completed standard of care adjuvant chemotherapy and whole breast irradiation. Assessments of sTILs and intraepithelial TILs (iTILs) was performed by H&E and qmIF from the initial biopsy and lumpectomy. Deep learning algorithms for tumor annotation and lymphocyte detection were used also to measure of iTILs. Spatial clustering analysis to measure the mean dispersion with iTILs was evaluated by calculating Ball-Hall index. Transcriptomic analysis of tumor-associated and immune genes was performed using the slide-mounted tissue. Seven patients were enrolled between Nov 2017-Apr 2019; 3 patients received pembro+IORT; and 4 patients received IORT alone. Initial H&E pathology assessment of sTILs demonstrated no significant changes between biopsy and lumpectomy in control patients. No consistent patterns of iTILs dispersion were observed in the control patients. Out of the 3 pembro-treated patients, one patient demonstrated a marked increase in sTILs with a shift from a neutrophil-rich to lymphoplasmacytic stromal infiltrate, where the mean dispersion of iTILs doubled. The 2 other pembro patients, one remained stable and one showed a slight increase in sTILs. The iTILs dispersion increased significantly in these patients. QmIF analysis showed overall increase in stromal immune cell infiltrate in all cases after Pembro treatment, with an increase in stromal CD68+ macrophage noted in all cases. Transcriptomic analysis showed increased expression of CD68 and CD163 after pembro treatment. In this preliminary analysis, we observe preoperative pembro-induced increases in sTILs with increased mean dispersion of iTILs in treatment-naïve TNBC. Further investigation is warranted to elucidate the impact of preoperative pembro in early stage TNBC and other potential therapeutic implications.