Fused PET/CT or CECT in Post-Therapeutic Assessment of Colorectal Cancer: A Study of the Efficacy of the Modality of Choice among Egyptian Patients

Abstract Background: One of the most common cancers, colorectal cancer accounts for several tumor-related mortalities; its high recurrence rates either as a local recurrence of the disease or as a distant metastatic disease (up to 35-40%) have been reported in the treated patients within the first two years following surgery. There has been heated debate over the modality of choice for imaging of the recurrent colorectal cancer. Aim of Study: This study investigates the diagnostic performance of fused Positron Emission Tomography/ Com-puted Tomography (PET/CT) in comparison to Contrast-Enhanced Computed Tomography (CECT) as a follow-up and restaging imaging tool for post-therapeutic colorectal cancers among Egyptian patients. Subjects and Methods: Data were collected from 84 Egyptian patients (26 females and 58 males, age ranges from 35 to 80 years) who were treated from colorectal cancers. They were referred to a private imaging center for evaluation of their disease recurrence by fused PET/CT. Results: Disease recurrence was categorized as operative bed recurrence/residual (incomplete therapeutic response), nodal, and distal metastases. The site of the tumor recurrence was predominantly seen in the rectosigmoid region in 31 patients (36.9%), followed by the ascending colon where it was present in 13 patients (15.4%), then the transverse colon as depicted in 9 patients (10.7%); the descending colon recurrence was noted in 6 patients (7.1%), and the caecal recurrence existed in only one patient (1.3%). With reference to the gold standard (the histopathology reports with a correlation to the clinical and the follow-up examinations for the patients as well as the tumor markers (CEA) levels), the fused PET/CT had sensitivity, specificity, positive predictive value, negative predictive value, and an overall accuracy of 93.33%, 83.33%, 93.33%, 83.33% & 90.48% respectively as compared to CECT (73.33%, 58.33%, 81.48%, 46.67%, 69.05% respectively). Conclusion: Our findings indicate that fused PET/CT is more effective than the CECT regarding the detection of operative bed recurrent disease and incomplete therapeutic responses. PET/CT may also offer a cost-effective whole-body scan for restaging of the recurrent diseases through an accurate detection of the nodal and distant metastases.