Transitioning from second-line to third-line therapy in metastatic colorectal cancer.

In the setting of metastatic colorectal cancer, many gains in patient outcomes have been achieved throughout the last 2 decades. A primary driver of these gains is access to more lines of therapy. In the palliative metastatic setting, all patients ultimately progress and require continued treatment sequencing. The goal is to expose patients to all lines of available therapies. It is now possible to better select patients for each therapy. Treatment selection algorithms encompass disease factors and patient characteristics, such as overall condition and age. Appropriate molecular profiling assessments should be available early in the treatment course, to drive decision-making and allow use of alternative therapies when possible. The transition to third-line therapy can be prompted by changes in imaging scans or laboratory tests, as well as changes in the patient's symptom burden. It can be problematic to delay initiation of third-line therapy when it is clinically indicated. Many oncologists will consider rechallenging patients with the same chemotherapy that did not work earlier. Although this strategy is reasonable, it should not necessarily take precedence over use of agents with proven efficacy in later lines of therapy in randomized clinical trials, such as regorafenib and trifluridine/tipiracil. Clinicians now commonly adjust the dose of regorafenib. A delay in the initiation of these third-line agents can allow the patient's performance status to decrease, thus diminishing the opportunity for a successful outcome.