Additional Support for the Introduction of Immune Cell Quantification in Colorectal Cancer Classification
Menée en Israël à partir de données portant sur 2 369 patients atteints d'un cancer colorectal, cette étude évalue l'association entre la présence intratumorale de lymphocytes T, une réaction lymphocytaire péritumorale de type Crohn et la survie des patients
Cancer is a complex and dynamic disease, and predicting clinical outcome is a major clinical challenge. Indeed, classification systems such as the traditional American Joint Committee on Cancer/Union Internationale Contre le Cancer (AJCC/UICC) TNM staging system provide insufficient prognostic information (1). A likely explanation for the predictive accuracy of the traditional TNM classification system is its reliance on the assumption that disease progression is tumor cell–autonomous and fails to incorporate the effects of the host immune response. Indeed, tumor progression has more recently been considered to be the result of a balance between an invasive tumor and the host immune/inflammatory response (2). Mounting evidence suggests that an enhanced lymphocytic reaction may be an informative prognostic indicator in cancer staging.
Colorectal cancer (CRC) is the fourth leading cause of cancer deaths worldwide. While clinical outcomes are largely dependent on stage at diagnosis and treatment, increasing evidence suggests that microsatellite instability (MSI) and host immune infiltration may also be highly informative prognostic indicators. Molecular genetic studies of CRC have identified high levels of MSI (MSI-H) in approximately 15% of CRCs. Histologic differences between MSI-H and microsatellite stable (MSS)/microsatellite-low (MSI-L) tumors have been well described, and the MSI-H phenotype has been associated with a better prognosis than tumors with an MSS or MSI-L phenotype. While the underlying drivers for the MSI-H survival advantage are not fully understood, the prognostic benefit has been at least partially attributed to the pronounced lymphocytic infiltration in this subset of cancers. Tumor-infiltrating lymphocytes (TILs) can trigger lysis of cancer cells by recognizing enhanced expression of abnormal tumor antigens presented by HLA molecules. The presence of TILs is more common in MSI-H than microsatellite-stable (MSS) tumors, perhaps because …
Journal of the National Cancer Institute , éditorial en libre accès, 2016