National Comprehensive Cancer Network (NCCN) guidelines suggest obtaining baseline imaging within six months of the initial procedure, but there are no guidelines beyond six months. Additional imaging should be guided by a change in symptoms and physical exams.
Baseline imaging is a way to account for treatment-related scarring, fibrosis, and inflammation. PET-CT is superior to CT-MRI alone in detecting residual disease, with a sensitivity of 94%, a negative predictive value of 95%, a specificity of 82%, and a positive predictive value of 75%. Reasons for false positives can include performance of imaging too soon after treatment, inflammation, infection, and normal physiological uptake of the tracer used.
The goal of imaging is to establish the “new normal,” which is important for future comparison, Dr. Pitman said. She added that there is room for improvement in having more standardized imaging protocols during surveillance. “There are no good NCCN guidelines for surveillance and follow-up,” she said. “We need cost-effective surveillance imaging guidlines that take into account disease site and individual patient factors.”