Pet Scan Surveillance for Early Detection of Colorectal Cancer
Abstract & Commentary
By William B. Ershler, MD, Editor
Synopsis: In a prospective randomized trial comparing post-surgical follow-up for patients with Stage III and IV colon cancer, PET-CT was found to detect recurrence earlier and to result in a greater number of patients eligible for surgical resection of isolated metastases when compared to conventional follow-up schedules that include CT scanning.
Source: Sobhani I, et al. Early detection of recurrence by 18FDG-PET in the follow-up of patients with colorectal cancer. Br J Cancer. 2008;98:875-880.
The value of using 18 fluorodeoxyglucose positron emission tomography (FDG-PET) for detecting tumor recurrence after surgery for colorectal cancer surgery has yet to be established. Sobhani and colleagues conducted a randomized trial that included 130 with Stage III or IV colon cancer patients divided into two groups: those followed by conventional exams, lab studies and imaging by CT versus those similarly followed, but with additional PET scanning. The two groups were matched at baseline. Of the 130 patients, 46 had developed recurrence during the follow-up period (two years). The recurrences were recognized in 25 in the FDG-PET and 21 in the conventional follow-up group. There were three false positive cases in the FDG-PET group that required additional studies (two laparoscopies and one MRI) and two patients developed peritoneal carcinomatosis that were not detected by FDG-PET.
There was no significant difference between the PET-followed versus conventional followed groups with regard to actuarial curves of recurrence; however, for all the patients with a recurrence, the time from baseline until detection of the recurrence was significantly shorter (P = 0.01) in the PET group (12.1+3.6 months) than in the conventional group (15.4 +4.9 months). Importantly, those followed by PET were considered to have resectable metastases more frequently (10 vs 2 patients), most likely because of the earlier detection. Thus, the authors conclude that regular FDG-PET monitoring in the follow-up of colorectal cancer patients may permit the earlier detection of recurrence and thereby influence overall survival by allowing resection of metastatic disease.
Commentary
The utility of PET scanning for the detection of colorectal cancer has been previously demonstrated (1, 2). However, the current report is the first prospective controlled randomized study of FDG-PET scanning in the follow-up patients with stage III or IV colon cancer. In this study, one third of the patients developed recurrence, and these occurred equally in both study groups. The important finding, however, was that the recurrences were discovered earlier in those followed by PET, leading to a greater chance of surgical resection in that group.
This study is provocative but needs validation. Patients were enrolled at a time when combined PET/CT was not in use, and the technological advances made since then would only enhance the likelihood that the findings would hold true. Yet, the bottom line is survival, and until it is clearly documented that those recognized to have metastatic disease earlier are afforded improved survival, either by surgery or other intervention, the use of PET for routine follow-up can not be recommended. The expense for such an approach would be overwhelming. What is needed is a large scale cooperative trial comparing PET/CT vs. CT alone as the imaging technique used in follow-up with both overall survival and healthcare costs (PET scans, additional surgeries, etc.) the outcome measures. Until then, PET/CT follow-up of colorectal cancer patients should be considered investigational and not routine.
References
1. Kamel IR, et al. Incremental value of CT in PET/CT of patients with colorectal carcinoma. Abdom Imaging. 2004;29(6):663-668.
2. Truant S, et al. Prospective evaluation of the impact of [18F]fluoro-2-deoxy-D-glucose positron emission tomography of resectable colorectal liver metastases. Br J Surg. 2005;92(3):362-369.
In a prospective randomized trial comparing post-surgical follow-up for patients with Stage III and IV colon cancer, PET-CT was found to detect recurrence earlier and to result in a greater number of patients eligible for surgical resection of isolated metastases when compared to conventional follow-up schedules that include CT scanning.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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