The AJCC/UICC-TNM pathological classification, based on the histological assessment of tumors, currently represents the prognostic standard for colon cancer; however, it proves insufficient for reliably estimating individual patient outcomes. Numerous studies have shown that the immune infiltrate present within the tumor provides prognostic information of paramount importance. On this basis, the Immunoscore was developed—a digital pathology assay that quantifies the densities of CD3+ T lymphocytes and CD8+ cytotoxic T lymphocytes at the tumor center and at its invasive margin, classifying patients into three risk categories: low, intermediate, or high Immunoscore. While the international validation of this tool had already been established in stage I to III colon cancer, its relevance remained to be specifically confirmed in the Asian population.
The study included 423 Asian patients with stage I to III colon cancer, drawn from care centers in China, India, and Japan, and initially enrolled in an international cohort of 2,681 patients led by the Society for Immunotherapy of Cancer (SITC). The association between the Immunoscore and prognosis was evaluated for time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS), using multivariate Cox models stratified by center and adjusted for sex, T stage, N stage, tumor sidedness, and MSI status.
The Immunoscore effectively stratifies patients into distinct risk categories, without any influence of age. Three-year recurrence-free survival rates reached 78.5%, 85.2%, and 98.3% for low, intermediate, and high Immunoscore, respectively (HR low vs high = 7.26; p = 0.0064). A high Immunoscore was significantly associated with prolonged TTR, OS, and DFS. In multivariate analysis, the association with TTR remained independent of clinical and pathological parameters (HR low vs intermediate+high = 2.22; p = 0.0269). This prognostic effect was confirmed across several subgroups, notably MSS tumors and stage II patients, including both low- and high-risk cases. Notably, MSI status itself appeared to be dependent on the Immunoscore, and the intratumoral immune environment was not altered by age in this population, in contrast with previous observations.
The authors acknowledge as limitations the heterogeneity of a population drawn from three large countries, as well as an insufficient sample size to precisely assess the benefit of chemotherapy according to Immunoscore categories. Nevertheless, this study reinforces the clinical utility of the Immunoscore in Asian patients with colon cancer and supports its integration into international guidelines, advocating for its adoption in routine practice.