[Interpretation of the updates of NCCN 2017 version 1.0 guideline for colorectal cancer]

The NCCN has recently released its 2017 version 1.0 guideline for colorectal cancer. There are several updates from this new version guideline which are believed to change the current clinical practice. Update one, low-dose aspirin is recommended for patients with colorectal cancer after colectomy for secondary chemoprevention. Update two, biological agents are removed from the neoadjuvant treatment regimen for resectable metastatic colorectal cancer (mCRC). This update is based on lack of evidence to support benefits of biological agents including bevacizumab and cetuximab in the neoadjuvant setting. Both technical criteria and prognostic information should be considered for decision-making. Currently biological agents may not be excluded from the neoadjuvant setting for patients with resectable but poor prognostic disease. Update three, panitumumab and cetuximab combination therapy is only recommended for left-sided tumors in the first line therapy. The location of the primary tumor can be both prognostic and predictive in response to EGFR inhibitors in metastatic colorectal cancer. Cetuximab and panitumumab confer little benefit to patients with metastatic colorectal cancer in the primary tumor originated on the right side. On the other hand, EGFR inhibitors provide significant benefit compared with bevacizumab-containing therapy or chemotherapy alone for patients with left primary tumor. Update four, PD-1 immune checkpoint inhibitors including pembrolizumab or nivolumab are recommended as treatment options in patients with metastatic deficient mismatch repair (dMMR) colorectal cancer in second- or third-line therapy. dMMR tumors contain thousands of mutations, which can encode mutant proteins with the potential to be recognized and targeted by the immune system. It has therefore been hypothesized that dMMR tumors may be sensitive to PD-1 inhibitors.