The CRYSTAL10 trial, testing adagracib and cetuximab, failed its primary endpoint despite a strong response rate. This suggests targeted RAS inhibitor doublets alone may be insufficient. The likely path forward involves combining them with a chemotherapy backbone, at least for the initial months of treatment, to achieve durable responses.

For HER2+ metastatic colorectal cancer, experts choose HER2-targeted therapies like TDXD or tucatinib/trastuzumab over standard second-line chemotherapy (FOLFIRI/BEV), despite label constraints. The rationale is the significantly higher response rate from targeting the oncogenic driver directly.

For BRAF V600E mutated colorectal cancer, data argues against the common practice of starting with chemotherapy and saving targeted therapy for later. Hitting the specific tumor biology hard and early with combination targeted agents leads to significantly better outcomes, including doubling overall survival.

Despite a study showing a minor hazard ratio benefit for a FLOT-like regimen over FOLFOX in the metastatic setting, experts advise against it. The significant increase in toxicity outweighs the small efficacy advantage, especially in symptomatic metastatic patients who are often nutritionally deficient and less able to tolerate aggressive chemotherapy.

The standard approach for first-line metastatic colorectal cancer is obsolete. Clinicians must test for and categorize patients into at least four, soon five, distinct biomarker-defined subgroups (MSI-high, BRAF V600E, RAS/RAF wild-type, HER2-positive, and the RAS-mutated "catch-all") to select the optimal initial therapy.

In third-line mCRC, drug selection is heavily guided by a patient's accumulated toxicities. For instance, a patient with bone marrow issues from prior chemotherapy might receive a VEGF inhibitor instead of another chemotherapy agent, prioritizing tolerability and quality of life.

HER2 amplification is a primary resistance mechanism to anti-EGFR therapies in colorectal cancer. Therefore, oncologists should avoid using drugs like panitumumab or cetuximab in HER2-positive patients, even if they are RAS wild-type, as these patients experience rapid progression on such regimens.

Learnings from trials like FIGHT-302 reveal that resistance to targeted therapy occurs both on-target (kinase domain) and off-target (e.g., MAP kinase pathway). The next research frontier is likely not just developing better inhibitors, but combining them with chemotherapy to potentially block multiple resistance pathways simultaneously from the outset.

While the ATOMIC trial combined FOLFOX with atezolizumab, clinicians should not de-escalate by simply dropping oxaliplatin. Historical data suggests single-agent 5-FU is ineffective and potentially harmful in MSI-high patients, a risk that is not presumed to be overcome by adding immunotherapy.