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Importance: Surveillance testing is performed after primary treatment for colorectal cancer (CRC), but it is unclear if the intensity of testing decreases time to detection of recurrence or affects patient survival. Objective: To determine if intensity of posttreatment surveillance is associated with time to detection of CRC recurrence, rate of recurrence, resection for recurrence, or overall survival. Design, Setting, and Participants: A retrospective cohort study of patient data abstracted from the medical record as part of a Commission on Cancer Special Study merged with records from the National Cancer Database. A random sample of patients (n=8529) diagnosed with stage I, II, or III CRC treated at a Commission on Cancer-accredited facilities (2006-2007) with follow-up through December 31, 2014. Exposures: Intensity of imaging and carcinoembryonic antigen (CEA) surveillance testing derived empirically at the facility level using the observed to expected ratio for surveillance testing during a 3-year observation period. Main Outcomes and Measures: The primary outcome was time to detection of CRC recurrence; secondary outcomes included rates of resection for recurrent disease and overall survival. Results: A total of 8529 patients (49% men; median age, 67 years) at 1175 facilities underwent surveillance imaging and CEA testing within 3 years after their initial CRC treatment. The cohort was distributed by stage as follows: stage I, 25.0%; stage II, 35.2%; and stage III, 39.8%. Patients treated at high-intensity facilities-4188 patients (49.1%) for imaging and 4136 (48.5%) for CEA testing-underwent a mean of 2.9 (95% CI, 2.8-2.9) imaging scans and a mean of 4.3 (95% CI, 4.2-4.4) CEA tests. Patients treated at low-intensity facilities-4341 patients (50.8%) for imaging and 4393 (51.5%) for CEA testing-underwent a mean of 1.6 (95% CI, 1.6-1.7) imaging scans and a mean of 1.6 (95% CI, 1.6-1.7) CEA tests. Imaging and CEA surveillance intensity were not associated with a significant difference in time to detection of cancer recurrence. The median time to detection of recurrence was 15.1 months (IQR, 8.2-26.3) for patients treated at facilities with high-intensity imaging surveillance and 16.0 months (IQR, 7.9-27.2) with low-intensity imaging surveillance (difference, -0.95 months; 95% CI, -2.59 to 0.68; HR, 0.99; 95% CI, 0.90-1.09) and was 15.9 months (IQR, 8.5-27.5) for patients treated at facilities with high-intensity CEA testing and 15.3 months (IQR, 7.9-25.7) with low-intensity CEA testing (difference, 0.59 months; 95% CI, -1.33 to 2.51; HR, 1.00; 95% CI, 0.90-1.11). No significant difference existed in rates of resection for cancer recurrence (HR for imaging, 1.22; 95% CI, 0.99-1.51 and HR for CEA testing, 1.12; 95% CI, 0.91-1.39) or overall survival (HR for imaging, 1.01; 95% CI, 0.94-1.08 and HR for CEA testing, 0.96; 95% CI, 0.89-1.03) among patients treated at facilities with high- vs low-intensity imaging or CEA testing surveillance. Conclusions and Relevance: Among patients treated for stage I, II, or III CRC, there was no significant association between surveillance intensity and detection of recurrence. Trial Registration: clinicaltrials.gov Identifier: NCT02217865.
Snyder et al. (Tue,) studied this question.