Spatial patterns in the tumor immune microenvironment as prognostic and predictive biomarkers of panitumumab (Pmab), fluorouracil and folinic acid (FU/FA) or FU/FA maintenance therapy following Pmab+FOLFOX induction in
RAS
wildtype (wt) metastatic colorectal cancer (mCRC): PanaMa (AIO KRK0212) trial.
Authors: Swoboda Susanna , Jarosch Armin , Karthaus Meinolf , Fruehauf Stefan , Graeven Ullrich , Fischer von Weikersthal Ludwig , Kasper Stefan , Sommerhäuser Greta , Jelas Ivan , Alig Annabel Helga Sophie , Stahler Arndt , Kurreck Annika , Held Swantje , Heinemann Volker , Horst David , Stintzing Sebastian , Trarbach Tanja , Modest Dominik Paul , Ballhausen Alexej 
Published: October 2024

3539

Background:
Patterns of tumor immune cell infiltration in the tumor microenvironment are prognostic biomarkers in CRC. Here, the spatially resolved tumor immune microenvironment was analyzed for prognostic and predictive impact in patients with
RAS
wt mCRC treated with FU/FA +/- Pmab maintenance after Pmab + FOLFOX induction (PanaMa AIO KRK0212 trial).
Methods:
A total of 12 immunological parameters (7 lymphocyte: CD3, CD8, CD45RO, FOXP3, CD20, Granzyme B, Perforin; 4 checkpoint: PD-1, PD-L1, IDO1, LAG3; and 1 monocyte: CD163) were quantified after immunohistochemistry using QuPath in spatially resolved (tumor invasive-margin [
Inv
], and center [
Cen
]) tissue-microarrays from available surgical tumor resections according to established local protocols. Parameters were analyzed according to percentile cutoffs, Immunoscore (combination of CD3 and CD8 in center and invasive-margin), and PD-L1 CPS. Median progression-free (PFS) and overall survival (OS) were estimated by Kaplan-Meier-method, log rank test and Cox regression.
Results:
In 194 patients with available surgical tumor resections, low expression of CD163 (HR: 0.717; 95% CI: 0.526-0.977; p = 0.036), and high expression of PD-1

(HR: 0.672; 95% CI: 0.491–0.921; p = 0.014) in the tumor center, were independent prognostic factors for prolonged PFS. The addition of Pmab to FU/FA maintenance was associated with longer PFS in patients with low expression of CD8
Inv
(HR: 0.224; 95% CI: 0.085-0.594; p = 0.004), LAG3
Cen
(HR: 0.489; 95% CI: 0.265-0.905; p = 0.025), CD163
Cen
(HR: 0.552; 95% CI: 0.346-0.883; p = 0.015), Immunoscore (HR: 0.501; 95% CI: 0.179-0.901; p = 0.024), and high expression of CD45
Cen
(HR: 0.403; 95% CI: 0.222-0.732; p = 0.003). In patients with CD45
Cen
-high and LAG3
Cen
-low, prolonged PFS translated also into a significant OS-prolongation. A positive Immunoactivation-score (defined as positivity in ≥ 2 predictive markers from univariate analysis) predicted significant benefit from additional Pmab as maintenance in terms of PFS (HR: 0.302; 95% CI: 0.161-0.567; p = <0.001) and OS (HR: 0.388; 95% CI: 0.195-0.772; p = 0.007).
Conclusions:
Several factors of the immune microenvironment were found to be prognostic factors for PFS and OS in patients with
RAS
wt mCRC. Of those, CD8, CD163, LAG3, CD45, Immunoscore, and an Immunoactivation-score were identified as independent predictive markers for benefit from the addition of Pmab to FU/FA maintenance therapy, suggesting that immune activation might be a crucial component of EGFR-antibody efficacy.