A new study being presented at the American Society of Clinical Oncology meeting in Chicago (Abstract #4020), may change treatment practice in about 25 percent of patients with colon cancer and is the basis for proposed changes to the way colorectal cancers will be staged.

This new study, using National Cancer Institute (NCI) SEER population-based statistic registries from 1992 to 2004, and phase III clinical trial data, shows that outcomes of patients with positive nodes (Stage III) in colorectal cancer interact, to a greater extent than previously thought, with how deeply the cancer penetrates the bowel wall.

Survival outcomes depend on the thickness of the primary cancer within or beyond the bowel wall in addition to whether nodes are positive or negative. A patient with a node positive ‘thin’ lesion (i.e., confined to the bowel wall) has a stage III cancer with better survival outcomes than a patient with a Stage II node negative ‘thick’ cancer that penetrates beyond the bowel wall. The current standard of practice for colon cancer patients is that all or most Stage III patients receive chemotherapy after surgical removal of their cancer, but Stage II patients do not routinely receive chemotherapy. In a separate National Cancer Data Base (NCDB) analysis, patients with Stage III colon cancers confined to the bowel wall who did not receive chemotherapy still had better survival than Stage II patients.

Guidelines for adjuvant therapy may need re-examination in future clinical trials as well as more research into the molecular basis for the interplay between a primary cancer's ability to penetrate the bowel wall and to spread to regional nodes.

Also, the survival of patients whose cancers invade beyond the bowel wall to involve adjacent structures or organs is worse than that of patients whose cancers merely penetrate to the surface of the bowel wall (the reverse had been thought to be true).