Cancer Science 2020: Post-surgical Colorectal Cancer (CRC) surveillance: PET/CT versus CT, Israel

Forty percent of CRC patients will fail, mostly within first two years following primary resection. Early detection of recurrent disease has been reported to improve their survival. The use of PET/CT during the follow-up process is equivocally superior to contrast enhanced CT. This study is a comparison of CT vs. PET/CT.

Colorectal cancer (CRC) is the third most common cancer in both sexes in South Korea and constitutes 12.7% of all cancers [1]. Although radical resection followed by chemotherapy and/or radiotherapy is an effective treatment, unexpected recurrence occurs in 30–50% of patients during follow-up . It has often been noted that earlier detection of local recurrence or distant metastasis would allow for more adequate treatment in patients with CRC. Identification of a secondary primary tumor as well as early detection of recurrence or metastasis is also crucial for determining the most appropriate therapeutic management in patients with cancer. In clinical practice, the postoperative status of patients with CRC is evaluated by physical examination, colonoscopy, carcinoembryonic antigen (CEA) level, and imaging studies including abdominal CT, MRI, and chest radiographs. Of these imaging modalities, abdominal CT is widely used, especially for locoregional recurrence, abdominopelvic lymph node metastasis, or hepatic metastasis, but occult lesions may be difficult to visualize. In addition, its field of view is limited to the pulmonary basal portion for the detection of lung metastasis.

The clinical usefulness of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) or PET/CT has been well established in patients with CRC for staging and follow-up .Several studies have demonstrated that the diagnostic performance of PET/CT is superior to that of other imaging techniques .However, these studies focused mainly on patients with either suspected recurrence or a conspicuous finding using other imaging modalities. According to the National Comprehensive Cancer Network (NCCN), clinical practice guidelines in oncology, routine PET, or PET/CT scans are not recommended for routine surveillance in patients with CRC .

Very few studies have considered whether PET/CT in postoperative surveillance programs affects the rate of detection in disease-free patients with CRC. In a prospective study by Sobhani et al. in which 130 patients who had undergone curative surgery were randomized to undergo either PET or a conventional workup during follow-up, among all patients with recurrence, the time until detection of recurrence was significantly shorter in the group that had undergone additional PET scanning than in the group that had undergone only the conventional workup.

In the present study, we assessed the value of PET/CT as a routine surveillance tool for detecting local and distant recurrence and secondary primary tumors in patients who undergo surgery for CRC and compared the accuracy of PET/CT to that of conventional imaging studies (CIS).

 

Methods: Medical records of all patients who had R0 radical colorectal surgery for Stage 1-3 disease between 1.2000 and 1.2016 were retrospectively reviewed. All patient who experienced recurrence and had both abdominal and/or chest CT scans followed by PET/CT within 60 days, were included in the study. A radiologist reviewed all images for disease recurrence. Findings consistent with recurrent disease were compared between the two modalities.

Results: Of 35 CT images 14 identified lung nodules; 10 of these 14 were confirmed malignant by FDG uptake. .9 CT images identified liver lesions, all were called “cystic”; PET/CT identified 10 liver cases; 6 of these 10 cases were called disease recurrence to the liver. One case was not demonstrated by CT while PET/CT did identify a disease recurrence in the liver. CT and PET/ CT both identified 7 peritoneal cases, but only 3 cases; were FDG avid (see table). PET/CT identified all anastomotic recurrences (N=4), these were noted only 3 times on CT.

Conclusions: A notable proportion of patients with negative findings on routine CT performed presented with a positive PET/CT. PET/CT should be employed in the follow-up protocol and replaced the CT.

Author(s): Mazarieb Mai

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