Combined 18-FDG-PET/Contrast-Enhanced CT in the Diagnosis of Recurrent Colorectal Cancer: A Prospective Monocentric Pilot Study

Abstract

Contrast-enhanced CT scan and 18DG-PET are used in the staging and surveillance of Colorectal Cancer (CRC). We here evaluate the feasibility and performances of systematically combining 18-FDG-PET and contrastenhanced CT whether as a stand-alone diagnostic examination, or as 2 separate examinations, for the early detection of recurrent colorectal cancer. 45 patients underwent 159 planned diagnostic follow-up sessions: 109 (68%) were performed as a combined modality during the same examination and 50 were performed as two separate examinations and acquired at different timepoints. Fourteen patients experienced recurrence during the study period. The sensitivity of 18-FDG-PET and contrast-enhanced CT scan in detecting a recurrent disease was 84.4% and 86.6 % respectively with a specificity of 96% and 97% respectively. 18-FDG-PET and contrast-enhanced CT findings’ were concordant in 79% of cases. The overall sensitivity and specificity in detecting CRC recurrence were 80% and 99% respectively in the combined procedure and 89% and 98% respectively in the two-time procedure. The positive predictive value of the procedure (combined or two-time procedure) for the detection of recurrent CRC was 100% with, however a shorter delay for decision with the combined [7.7 vs. 12.2 days] (p<0.05). The combined procedure is feasible in almost 2/3 of cases. When compared to the two-time procedure, it is performant in detecting recurrent CRC with shorter delay to therapy.