Defining Treatment Failure and Selecting Second-Line Therapy in mCRC

This episode, “Defining Treatment Failure and Selecting Second-Line Therapy in mCRC,” features the panel examining how disease biology, treatment response, and molecular characteristics guide the transition to second-line care. Dr. Kazmi explains that the threshold for calling first-line treatment a failure depends on the biology and burden of disease. A patient with low-volume disease who has achieved prolonged control on maintenance therapy may be approached differently from someone with high-volume disease and a short response to initial treatment. Symptoms, treatment-related toxicity, quality of life, tumor markers such as CEA, circulating tumor DNA, and the pace of radiographic progression can all contribute to the decision to change therapy.

The discussion also addresses the evolving role of ctDNA. Dr. Kazmi sees value in minimal residual disease assessment and surveillance after resection and in detecting emerging resistance during anti-EGFR therapy. However, he notes that the ability to act on these findings remains limited in routine colorectal cancer care.

Dr. Fakih then reviews second-line selection. Prior therapy, molecular profile, performance status, and treatment goals all influence the next step. Many patients switch chemotherapy backbones, while others may have targeted options based on RAS, HER2, KRAS G12C, or other molecular findings. The episode highlights how second-line sequencing increasingly requires integration of prior treatment history, molecular subtype, disease behavior, and patient-specific considerations.

In the next episode, “Planning for Third-Line Therapy and Treatment Rechallenge in mCRC,” the panel discusses when to begin preparing for later-line treatment and whether previously used therapies can be revisited.