Positron emission tomography/computed tomography for early treatment response evaluation in metastatic colon cancer.

Abstract

614 Background: Treatment options for metastatic colon cancer (mCC) are widening. We prospectively evaluated serial 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography/ computed tomography (PET/CT) and measurements of tissue inhibitor of metalloproteinases type 1 (TIMP-1), carcinoembryonic antigen (CEA) and urokinase plasminogen activator receptor domain I [uPAR(I)] for early assessment of treatment response in mCC patients. Methods: Thirty-three mCC patients scheduled for first line chemotherapy with capecitabine, oxaliplatin (CAPOX) and bevacizumab participated; 27 were evaluated by PET/CT before treatment, after one and four treatment series. Morphological and metabolic response was independently assessed according to Response Evaluation Criteria In Solid Tumours (RECIST1.1) and EORTC PET criteria. Plasma TIMP-1, plasma uPAR(I) and serum CEA were determined. Results: Metabolic response after one treatment course predicted the ability of CAPOX and bevacizumab to induce morphological response after four treatment series with a sensitivity of 80 %, specificity of 69 % and an Odds Ratio of 13.9 [CI 1.9; 182]. Early metabolically stable or progressive disease was associated with shorter progression-free survival (PFS) (hazard ratio (HR) = 3.2 [CI 1.3; 7.8]). Biomarker levels at early evaluation were associated to shorter PFS (TIMP-1 per unit increase on a log-2 transformed ng/mL scale: HR = 2.23 [CI 1.20; 4.14]; uPAR(I) per 25 fmol/mL increase: HR = 1.36 [CI 1.03; 1.79]). Conclusions: This monocentric study demonstrated predictive value of early metabolic PET response and prognostic value of TIMP-1 and uPAR(I) levels in mCC treated with CAPOX and bevacizumab. Results support investigation of PET/CT, TIMP-1 and uPAR(I) guided early treatment adaptation in mCC.