HER2 in Colorectal Cancer: The Long and Winding Road From Negative Predictive Factor to Positive Actionable Target

Human epidermal growth factor receptor 2 (HER2) is a well-known oncogenic driver in different tumors and an approved therapeutic target in breast and gastroesophageal cancer. In metastatic colorectal cancer, only 3% to 5% of patients present with HER2 alterations: somatic mutations and amplifications. HER2 was first assessed as a biomarker of resistance to anti-EGFR therapy; however, in more recent years, its role as a potential actionable target has emerged. In this article, we discuss the predictive and prognostic value of HER2 in metastatic colorectal cancer, its emerging role as an actionable therapeutic target, and its possible future developments.

The Optimal Duration of Adjuvant Chemotherapy in Colon Cancer

Adjuvant chemotherapy for colon cancer (UICC stage II and III) has been under investigation over the last 30 years, regarding treatment duration and regimens. In this review, choice of regimen, its duration, possible limitations and future perspectives are discussed. Monotherapy with 5-fluorouracil was followed by addition of oxaliplatin, resulting in improved 3-yr disease free survival (DFS) and overall survival (OS) rates, but also increased peripheral sensory neurotoxicity (PSN). The International Duration Evaluation of Adjuvant therapy (IDEA) collaboration demonstrated less toxicity, especially PSN, when shortening treatment duration to 3 months. However, formally, the anticipated non-inferiority of 3 months with fluoropyrimidine (FP)/oxaliplatin over 6 months (at 3-yr DFS) was not met for all patients groups, although subgroup analyses showed non-inferiority with capecitabine/oxaliplatin (CAPOX) rather than with FOLFOX, and also in relation to the prognostic information (e.g., clinical low-risk group, pT1-3 N0). In addition, first data of newer parameters like Immunoscore® and ctDNA show promising results as stratification parameters. Further investigations to better define clinical risk groups and prognostic factors are mandatory. Besides this, individual decision-making of treatment intensity (FP or FP/oxaliplatin) and duration should always consider patient characteristics and preferences, also given the absolute relatively small differences and their clinical relevance.