Prognostic assessment of resected colorectal liver metastases integrating pathological features, RAS mutation and Immunoscore

Abstract

Surgical resection of colorectal liver metastases combined with systemic treatment aims to maximize patient survival. However, recurrence rates are very high postsurgery. In order to assess patient prognosis after metastasis resection, we evaluated the main patho-molecular and immune parameters of all surgical specimens. Two hundred twenty-one patients who underwent, after different preoperative treatment, curative resection of 582 metastases were analyzed. Clinicopathological parameters, RAS tumor mutation, and the consensus Immunoscore (I) were assessed for all patients. Overall survival (OS) and time to relapse (TTR) were estimated using the Kaplan-Meier method and compared by log-rank tests. Cox proportional hazard models were used for uni- and multivariate analysis. Immunoscore and clinicopathological parameters (number of metastases, surgical margin, histopathological growth pattern, and steatohepatitis) were associated with relapse in multivariate analysis. Overall, pathological score (PS) that combines relevant clinicopathological factors for relapse, and I, were prognostic for TTR (2-year TTR rate PS 0-1: 49.8.% (95% CI: 42.2-58.8) versus PS 2-4: 20.9% (95% CI: 13.4-32.8), hazard ratio (HR) = 2.54 (95% CI: 1.82-3.53), p < 0.0000; and 2-year TTR rate I 0: 25.7% (95% CI: 16.3-40.5) versus I 3-4: 60% (95% CI: 47.2-76.3), HR = 2.87 (95% CI: 1.73-4.75), p = 0.0000). Immunoscore was also prognostic for OS (HR [I 3-4 versus I 0] = 4.25, 95% CI: 1.95-9.23; p = 0.0001). Immunoscore (HR [I 3-4 versus I 0] = 0.27, 95% CI: 0.12-0.58; p = 0.0009) and RAS mutation (HR [mutated versus WT] = 1.66, 95% CI: 1.06-2.58; p = 0.0265) were significant for OS. In conclusion, PS including relevant clinicopathological parameters and Immunoscore permit stratification of stage IV colorectal cancer patient prognosis in terms of TTR and identify patients with higher risk of recurrence. Immunoscore remains the major prognostic factor for OS.

Keywords: Immunoscore; chemotherapy related liver injury; colorectal cancer; colorectal liver metastases; histopathological growth pattern; pathological score; steatohepatitis; tumor microenvironment; tumor regression grading.

Figure 1

Pathological parameters analyzed. (A) TRG in colorectal liver metastases (H&E). TRG 1 (complete response to the treatment with maximal fibrosis); TRG 2 (major response with only scattered neoplastic cells in a fibrotic context); TRG 3 (minor response with more residual tumor cells but fibrosis predominates); TRG 4 (absence of response with residual cancer cells predominating over fibrosis); and TRG 5 (no signs of regression). (B) Four different HGPs (H&E). Desmoplastic HGP (metastasis is separated from the surrounding liver parenchyma by a desmoplastic rim), pushing HGP (metastasis grows by compressing the liver parenchyma), replacement HGP (metastases growth preserves the architecture of the hepatic tissue), and mixed HGP (a mix of two or more patterns. Desmoplastic HGP (arrow) and replacement HGP (arrowhead) are shown here). (C) Chemotherapy related liver injury (CALI) is classified in: sinusoidal obstructive syndrome (SOS, H&E) (varying degrees of endothelial damage); NRH (reticulmin staining) (nodularity aspect of the liver parenchyma without fibrosis); and steatohepatitis (H&E) (steatosis, ballooning and lobular inflammation).

Figure 2

Intrametastatic immune infiltrate. Representative slides of two metastatic lesions with high (up) and low (down) T‐cell (CD3+) density. The infiltrate is shown with a high to low density color gradient scaling from red to white, respectively. The immunohistochemical density of CD3 positive lymphocytes (in brown) in the invasive margin (IM) of the lesion is shown for a tile.

Figure 3

The relative importance of clinicopathological factors, RAS mutational status and Immunoscore for patient survival. (A–D) Assessment of the relative importance of each parameter to survival risk using the chi squared proportion (χ²) test for clinical parameters + Immunoscore for TTR (left) and OS (left). (A,B) Model with individual parameters: steatohepatitis, HGP, lesion number, R status, RAS status and Immunoscore. (C,D) Model with the PS, RAS status and Immunoscore. The significance of the Cox multivariate regression model was evaluated with the Wald P value. P value <0.05 was considered significant.

Figure 4

The impact on survival of Immunoscore and PS. Kaplan–Meier curves for TTR and OS according to Immunoscore (A,B), PS (C,D) Immunoscore and PS (E,F). Immunoscore (I) was determined based on the minimum infiltrated metastases. Five groups of patients were defined based on the density of CD3 and CD8 in the center and the invasive margin of the metastasis (minimum P value cut‐off): I 0 (0Hi), I 1 (1Hi), I 2 (2Hi), I 3 (3Hi), I 4 (4Hi). Immunoscore (I) groups were merged as: I0 (black), I 1–2 (green) and I 3–4 (red). (C,D) PS includes: more than three lesions, R1 positive margin, steatohepatitis, replacement or mixed HGP. One point was given for each parameter when present. PS groups were merged: PS 0–1 (red), PS 1 (green) and PS 2–4 (black). (E,F) Immunoscore and PS groups: I 3–4, PS 0–1 (red); I 3–4, PS 2–4 (green); I 0–2, PS 0–1 (blue); I 0–2, PS 2–4 (black).