Despite its recognized role in breast cancer (BC), the complexity of immune microenvironment remains largely unexplored. Multiplex immunohistochemistry (mIHC) holds opportunity to more comprehensively assess BC immunity, potentially providing information to improve immunotherapy.
In the neoadjuvant phase II SOLTI-1114 PAMELA trial (NCT01973660), 151 HER2+ BC patients received lapatinib and trastuzumab, plus hormonal therapy if HR+. Baseline (BSL, n=66) and day-15 (D15, n=54) biopsies from 76 patients were analyzed using a custom mIHC 6-plex panel, including immune subtyping (CD3, CD4, CD8, FOXP3), localization (keratin for tumor mask), and activity (Ki67 for proliferation). Immune cell density (cells/mm2) and localization were determined by digital image analysis and classified in: intratumor (A), proximal peritumor (B - < 10um; C - 10 to 30um from tumor) and distal peritumor stroma (D). Intrinsic subtyping was determined at the same timepoints using the PAM50 predictor (nCounter).
Both at BSL and D15, no significant difference in immune subpopulation densities was observed according to PAM50 subtype. At both timepoints, fraction of proliferating (Ki67+) immune cells (all subpopulations) differed significantly according to subtype (basal-like tumors showing the highest and luminal tumors showing the lowest fraction of proliferating cells, p varying from <0.001 to 0.031). Tumors achieving a pCR showed numerically higher densities of CD3+, CD8+ and FOXP3+ cells. Association with pCR was stronger at D15 and for immune cells intratumor/more proximal to tumor (Table). Overall, at D15, tumors achieving pCR showed higher CD3+ density (p=0.03) and higher ratio in Ki67+CD8+/Ki67+FOXP3+ (p=0.03). Table: 8P
Odds ratios (95% CI) for pCR for 1000 cells/mm2 increases in immune cell density according to subpopulation, timepoint, and localization
|Immune cell subpopulation||CD3+||1.37 (0.97-1.94)||1.31 (0.95-1.81)||1.35 (0.93-1.96)||1.02 (0.48-2.17)||1.38 (1.04-1.82)||1.25 (1.01-1.55)||1.31 (0.98-1.73)||1.79 (0.87-3.65)|
|CD8+||1.51 (0.66-3.50)||1.33 (0.74-2.40)||1.39 (0.69-2.83)||1.00 (0.26-3.76)||1.61 (1.09-2.39)||1.42 (1.01-2.00)||1.59 (0.97-2.61)||2.87 (0.73-11.29)|
|FOXP3+||1.12 (0.92-1.36)||1.28 (0.88-1.87)||1.43 (0.82-2.48)||0.26 (0.01-7.13)||1.10 (0.99-1.23)||1.19 (1.01-1.41)||1.31 (0.99-1.73)||4.61 (0.32-66.13)|
In early HER2+ BC, immune cells show differential proliferation patterns according to tumor biology. Number of immune cells spatially interacting with tumor after priming by anti-HER2 therapy was associated with pCR.
Clinical trial identification
Legal entity responsible for the study
Vall d'Hebron Institute of Oncology (VHIO).
G. Griguolo: Travel/Accommodation/Expenses: Pfizer. A. Prat: Honoraria (self), Advisory/Consultancy: Pfizer; Honoraria (self), Advisory/Consultancy, Research grant/Funding (institution), immediate family member being employed by Novartis: Novartis; Honoraria (self), Advisory/Consultancy, Research grant/Funding (institution): Roche; Honoraria (self): MSD Oncology; Honoraria (self): Lilly; Honoraria (self), Travel/Accommodation/Expenses: Daiichi Sankyo; Advisory/Consultancy: NanoString Technologies; Advisory/Consultancy: Amgen; Advisory/Consultancy: Bristol-Myers Squibb. P. Nuciforo: Advisory/Consultancy: Bayer; Advisory/Consultancy, Speaker Bureau/Expert testimony: MSD Oncology; Advisory/Consultancy, Speaker Bureau/Expert testimony: Novartis. All other authors have declared no conflicts of interest.