Two major molecular pathways of colorectal carcinogenesis, chromosomal instability (CIN) and microsatellite instability (MSI), are considered to be mutually exclusive. Distinguishing CIN from MSI-high tumors has considerable therapeutic implications, because patients with MSI-high tumors can derive considerable benefit from immune checkpoint inhibitors, and tumors that evolved through the CIN pathway do not respond to these agents. Familial adenomatous polyposis (FAP) is a genetic syndrome that is defined by a mutation in the APC gene and is thought to lead to carcinogenesis through the CIN pathway. Here, we report a case of a young woman with FAP who was treated for medulloblastoma as a child and developed advanced MSI-high colon cancer as a young adult. Her response to second-line immunotherapy enabled resection of her colon cancer, and she is free of disease >10 months after surgery. This case highlights the potential for overlap between the CIN and MSI carcinogenic pathways and associated therapeutic implications.
Steven M. Blum, William R. Jeck, Lindsay Kipnis, Ronald Bleday, Jonathan A. Nowak, and Matthew B. Yurgelun
Al B. Benson III, Alan P. Venook, Mahmoud M. Al-Hawary, Nilofer Azad, Yi-Jen Chen, Kristen K. Ciombor, Stacey Cohen, Harry S. Cooper, Dustin Deming, Ignacio Garrido-Laguna, Jean L. Grem, Andrew Gunn, J. Randolph Hecht, Sarah Hoffe, Joleen Hubbard, Steven Hunt, William Jeck, Kimberly L. Johung, Natalie Kirilcuk, Smitha Krishnamurthi, Jennifer K. Maratt, Wells A. Messersmith, Jeffrey Meyerhardt, Eric D. Miller, Mary F. Mulcahy, Steven Nurkin, Michael J. Overman, Aparna Parikh, Hitendra Patel, Katrina Pedersen, Leonard Saltz, Charles Schneider, David Shibata, John M. Skibber, Constantinos T. Sofocleous, Eden Stotsky-Himelfarb, Anna Tavakkoli, Christopher G. Willett, Kristina Gregory, and Lisa Gurski
This selection from the NCCN Guidelines for Rectal Cancer focuses on management of malignant polyps and resectable nonmetastatic rectal cancer because important updates have been made to these guidelines. These recent updates include redrawing the algorithms for stage II and III disease to reflect new data supporting the increasingly prominent role of total neoadjuvant therapy, expanded recommendations for short-course radiation therapy techniques, and new recommendations for a “watch-and-wait” nonoperative management technique for patients with cancer that shows a complete response to neoadjuvant therapy. The complete version of the NCCN Guidelines for Rectal Cancer, available online at NCCN.org, covers additional topics including risk assessment, pathology and staging, management of metastatic disease, posttreatment surveillance, treatment of recurrent disease, and survivorship.