The Evaluation of Serial Marker Measurements for Monitoring Patients at Risk of Recurrent Cancer: Application to Colorectal Cancer
In this chapter, three aspects of serial monitoring of cancer patients after resection are reviewed: (1) demonstrating that the marker profile is associated with increased risk of recurrence, (2) assessing the possible benefit of surgery in the marker-positive patient without other evidence of disease, and (3) evaluating the potential benefit of the marker for the entire population of patients with resected tumors. Points (2) and (3) are discussed with reference to colorectal cancer.
For demonstrating an association of marker profile with risk of recurrence, new statistical methods that take the time of recurrence into account are recommended, and design features for ideal clinical studies are discussed.
Available data suggest that second-look surgery following resection of colorectal cancer will improve five-year survival rates for the carcinoembryonic antigen (CEA) marker-positive, clinically negative patient from about 12% to about 21%, but the clinical evidence is scanty, especially regarding survival rates in patients with repeat resections. Sample size calculations for a clinical trial comparing immediate second-look surgery with watchful waiting suggest that such a trial is not feasible and indicate a need for more of the preliminary type of data used in this paper. The desirability of surgery for the marker-positive, clinically negative patient requires periodic reassessment because improvements in diagnostic technique are rapidly changing the definition of “clinically negative.” The surgeon may encounter a decreasing proportion of untreatable recurrences and an increasing proportion of recurrence-free patients in future operations on marker-positive, “clinically negative” patients.
An extension of these analyses to all patients with resected disease shows that very little survival benefit is lost by eliminating or reducing conventional clinical follow-up. Instead, one can rely on a combined program of education to alert patients to important symptoms and of periodic CEA monitoring. This program captures practically all the survival benefit that could be obtained from a much more costly and inconvenient program, including both CEA monitoring and clinical follow-up.
KeywordsWatchful Waiting Marker Profile Marker Measurement Repeat Resection Recurrent Colorectal Cancer
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