Neoadjuvant chemotherapy is associated with a transient increase of intratumoral T-cell density in microsatellite stable colorectal liver metastases

Abstract

Patients with colorectal liver metastases (CLM) commonly receive neoadjuvant chemotherapy (NACT) prior to surgical resection. NACT may induce immunogenic cell death with subsequent recruitment of T-cells to the tumor microenvironment, which could be exploited by immune checkpoint inhibition (ICI). In theory, this could expand the use of ICI to obtain responses also in microsatellite stable colorectal cancer, but evidence to suggest optimal treatment schedules are lacking. In this study, densities of total-, cytotoxic-, helper- and regulatory T-cells were quantified by immunohistochemistry in resected CLM from 92 patients included in the OSLO-COMET trial (NCT01516710). All but one patient had microsatellite stable tumors (91/92). Associations between T-cell densities and clinicopathological parameters were analyzed. Fluoropyrimidine-based NACT (in most cases with addition of oxaliplatin or irinotecan) was administered to 45 patients completed median 8 weeks prior to surgical resection. No overall association was found between NACT administration and intratumoral T-cell densities. However, within the NACT group, a short time interval (<9.5 weeks) between NACT completion and CLM resection was strongly associated with high intratumoral T-cell densities compared to the long-interval and no NACT groups (medians 491, 236, and 292 cells/mm2, respectively; P < .0001). The results from this study suggest that the observed increase in intratumoral T-cells after NACT administration may be transient. The significance of this finding should be further explored to ensure that optimal treatment schedules are chosen for studies combining cytotoxic chemotherapy and ICI.

Keywords: Liver metastases; colorectal cancer; immune check-point inhibition; immunogenic cell death; neoadjuvant chemotherapy; t-cell densities.

Figures

Figure 1.

Scatter plot showing the correlation between the total number of T-cells (Ttot) and the sum of cytotoxic and helper T-cell subtypes (CTL and TH) in all tumor regions and adjacent liver tissue. The diagonal line indicates linear regression analysis (R2 = 0.99), suggesting that CTL and TH corresponded well to Ttot.

Figure 2.

Dot density plots of intratumoral T-cell densities (cells/mm2) in the NACT subgroups. Light gray circles, No-NACT group (n = 57 tumors); dark gray triangles, short-interval group (n = 54 tumors); and open circles, long-interval group (n = 33 tumors). Group median is indicated by the horizontal lines. Subgroups are compared pairwise, and significant differences are indicated: *, P < .05; **, P < .01; ***, P < .001; ****, P < .0001. a) Ttot, total amount of T-cells, b) CTL, cytotoxic T-cells, c) TH, helper T-cells, d) Treg, regulatory T-cells

Figure 3.

Representative immunohistochemistry images from the intratumoral region of two cases with colorectal liver metastasis. Sections were stained to detect the total amount of T-cells (CD3+) and cytotoxic T-cells (CD8+). On serial slides, corresponding hotspots were selected to quantify T-cells for each case, shown by the black rectangles. (Images were acquired at 4x magnification and the black line represents 0.2 mm). Case 1 (short-interval NACT subgroup): (a) total number of T-cells. (b) cytotoxic T-cells. Case 2 (no NACT subgroup): (c) total number of T-cells. (d) cytotoxic T-cells

Figure 3.

Representative immunohistochemistry images from the intratumoral region of two cases with colorectal liver metastasis. Sections were stained to detect the total amount of T-cells (CD3+) and cytotoxic T-cells (CD8+). On serial slides, corresponding hotspots were selected to quantify T-cells for each case, shown by the black rectangles. (Images were acquired at 4x magnification and the black line represents 0.2 mm). Case 1 (short-interval NACT subgroup): (a) total number of T-cells. (b) cytotoxic T-cells. Case 2 (no NACT subgroup): (c) total number of T-cells. (d) cytotoxic T-cells