Abstract
Stratification of metastatic colorectal cancer (mCRC) patients is mostly based on clinical and biological characteristics. This study aimed to validate the prognostic value of 18F-FDG PET/CT-based biomarkers such as baseline whole-body metabolically active tumor volume (WB-MATV) and early metabolic response (mR) in mCRC. Methods: The development cohort included chemorefractory mCRC patients enrolled in two prospective Belgian multicenter trials evaluating last-line treatments (multikinase inhibitors). The validation cohort included mCRC patients from an Italian center treated with chemotherapy and bevacizumab as first-line. Baseline WB-MATV was defined as the sum of metabolically active volumes of all target lesions identified on the baseline 18F-FDG PET/CT. Early metabolic response (mR) assessment was performed following usual response criteria (PERCIST–30%, PERCIST–15%, EORTC) and the so-called CONSIST method, which defines response as a decrease of SULmax ≥ 15% for all target lesions. Baseline WB-MATV and early mR assessment were investigated along with usual clinical factors and correlated with overall and progression-free survival (OS/PFS). Results: Clinical factors, baseline WB-MATV and early mR were evaluable in 192/239 and 94/125 patients of the development and validation cohorts, respectively. Except for PERCIST–30%, all response methods were equivalent in terms of outcome prediction and CONSIST was found to be the most accurate. Baseline WB-MATV and early mR using CONSIST method were independent prognostic parameters after adjustment for clinical factors in the development and validation sets for both OS (HR WB-MATV: 1.87 (1.17-2.97), P = 0.005, and HR early mR: 1.79 (1.08-2.95), P = 0.02 for the validation set), and PFS (HR WB-MATV: 1.94 (1.27-2.97), P = 0.002, and HR early mR: 1.69 (1.04-2.73), P = 0.03 for the validation set). Conclusion: Baseline WB-MATV and early mR are strong independent prognostic biomarkers for OS/PFS in mCRC, regardless of treatment received. Therefore, combining these biomarkers improves risk stratification for OS/PFS in mCRC.
- Oncology: GI
- PET/CT
- <sup>18</sup>F-FDG PET/CT-based biomarkers
- early metabolic response
- metabolically active tumor volume
- metastatic colorectal cancer
- Copyright © 2021 by the Society of Nuclear Medicine and Molecular Imaging, Inc.