Evaluation of CEA density as a prognostic factor for percutaneous ablation of pulmonary colorectal metastases

Purpose: This study measured the F-18 FDG and C-11 Choline activity on PET/CT scans before and after percutaneous ablation of bone tumors comparing these values to local tumor recurrence and pain/functional status in the ablated region. Materials: Using our institutional tumor ablation database, patients with PET/CT scans acquired before and after bone tumor ablation procedures performed between January 1, 2002 and September 1, 2015 were identified. F-18 FDG and C-11 Choline PET/CTs were evaluated for preand post-ablation maximum SUV with readers blinded to clinical information except for the location of the targeted bone metastasis. For SUV determination, a region of interest (ROI) incorporating the lesion was manually placed by the radiologist. The SUVmax was subtracted from blood pool (right atria), and a ratio comparing SUVmax before and after ablation (SUVmax post-ablation/SUVmax pre-ablation) was calculated. Clinical information, including patient demographics, pain level and function, and oncologic outcome, was obtained from the electronic medical record. Local tumor recurrence was defined as any growth on CT, MRI, or by tissue sample. Results: This study identified 96 patients with a mean age of 58.3 years (SD 15.4 years, range 26-83) at time of bone ablation with a PET positive bone lesion prior to ablation and at least one PET/CT post ablation. Eight-one of the patients were followed with F-18 FDG PET and 15 with C-11 Choline PET. Patients with no evidence of local tumor recurrence and overall better functionality/decreased pain had a lower SUVmax ratio, mean 0.37±0.0.780, relative to patients who had evidence of local recurrence and worsening pain, mean 2.04± 1.68 (p o0.04). There was no correlation between SUV and interval between ablation procedure and post-ablation PET/CT (mean 516.5 days, range 15-2081) with an R value of 0.0179. Conclusions: Patients with no evidence of locally recurrent disease and decreased pain had significantly lower SUVmax ratios than with evidence of recurrence independent of duration of follow up. This suggests that any increase in PET radiotracer uptake within the ablation bed is concerning for recurrence regardless of the imaging time interval post ablation.