Can 18F-FDG PET/CT scan change treatment planning and be prognostic in recurrent colorectal carcinoma? A prospective and follow-up study

Abstract

Objective: To prospectively study whether in patients with resected primary colorectal cancer fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) examination could diagnose the stage, specify treatment procedure and be prognostic. Subjects and methods: This prospective study included 75 patients with resected primary colorectal adenocarcinoma referred for 18F-FDG PET/CT to the National PET Center, at the Clinical Center of Serbia, Belgrade, from January 2010 to May 2013. Findings of 18F-FDG PET/CT were compared to findings of subsequent histopathological examinations or with results of clinical and imaging follow-up. Patients were followed after PET/CT examination for a mean follow-up time of 16.7±5.9 months. Results: In the detection of recurrent disease 18FFDG PET/CT showed overall sensitivity, specificity, PPV, NPV and accuracy of 96.6%, 82.4%, 94.9%, 87.5% and 93.3%, respectively. In the detection of stages I and II sensitivity, specificity and accuracy of 18F-FDG PET/CT were: 88%, 96.6% and 94.7%, respectively, and in the detection of stages III and IV sensitivity, specificity and accuracy were 94.9%, 87.5% and 93.3%, respectively. These findings prevented or changed intended surgical treatment in 12/32 cases. Univariate and multivariate Cox proportional regression analyses revealed that metastatic recurrence (stages III and IV) was the only and independent prognostic factor of disease progression during follow-up (P=0.012 and P=0.023, respectively). Although, survival seemed better in patients with local recurrence compared to metastatic recurrent disease, this difference did not reach significance (Log-rank test; P=0.324). In addition, progression-free survival time was significantly longer in patients in whom 18F-FDG PET/CT scan led to treatment changes (Log-rank test; P=0.037). Conclusion: 18F-FDG PET/CT was sensitive and accurate for the detection and staging of local and metastatic recurrent colorectal carcinoma, with higher specificity in the detection of local recurrences. The 18F-FDG PET/CT scan induced treatment changes in 30/75 patients, including 12/32 patients in which surgical treatment was previously planned, and progression free survival time was significantly longer in these patients.