Colon cancer: did the care follow the guidelines?

Colon cancer treatment follows the stage. Stages I and II usually mean surgery, with chemotherapy reserved for select higher-risk cases. Stage III means surgery plus adjuvant chemotherapy. Stage IV means systemic therapy steered by the tumor's biology. The pathway is well settled, and the places care goes off it are fairly predictable.

The decisions that matter

• MMR/MSI testing. Every colon cancer should be tested for mismatch-repair deficiency (reported as dMMR or MSI-high). The result changes chemotherapy decisions in early disease and opens the door to immunotherapy in advanced disease. A chart with no MMR result anywhere is itself a finding.
• Adjuvant chemotherapy at stage III. Once the cancer reaches the lymph nodes, surgery alone is not the standard. The guidelines call for offering adjuvant chemotherapy (FOLFOX or CAPOX for most patients) after resection.
• RAS and BRAF testing before targeted drugs. In metastatic disease, the tumor should be tested for KRAS, NRAS, and BRAF mutations before anti-EGFR antibodies enter the picture.
• Anti-EGFR drugs only where they work. Cetuximab and panitumumab do not work in RAS-mutated tumors, and they underperform in cancers arising on the right side of the colon. Giving them anyway exposes a patient to side effects and cost for little or no benefit, and the guidelines say so.
• Immunotherapy for dMMR/MSI-high metastatic disease. For this biology, the guidelines put immunotherapy (such as pembrolizumab) in first line. Patients in this group who cycle through chemotherapy regimens without immunotherapy ever coming up are being treated off the pathway.

What a deviation looks like

Cetuximab prescribed for a KRAS-mutated tumor. A stage III resection followed by no chemotherapy and no documented discussion of it. An MSI-high metastatic patient on a third chemotherapy regimen with immunotherapy never mentioned. None of these findings proves negligence on its own, and each one cites the guideline page it comes from, so the question is easy to put to a clinician or an attorney.