Cancer Treatment Today

Lay Summary: PET is an acceptable way to stage colon cancer, although some resistance remains.

More recently NCCN has been more supportive of PET in colorectal cancer staging. It supports PET in the situation of rising CEA and no identified recurrence but also in some other settings (p.13). CMS guidelines state that PET would rarely be used in the diagnosis of colorectal cancer. However, starting July 1, 2001, HCFA, now called the Centers for Medicare and Medicaid Services (CMS), is covering FDG-PET imaging for diagnosis, staging, and restaging of colorectal cancer.

Abdel-Nabi and coworkers evaluated 48 patients with either biopsy-proven (44 patients) or a high clinical suspicion for colorectal cancer. These patients were scheduled to undergo exploratory laparotomy. FDG-PET detected all intraluminal carcinomas, and false-positive results were obtained in 4 of 7 patients who did not have cancer. Three of the 4 patients with false-positive results had inflammatory bowel disease, and 1 patient had undergone a polypectomy. Lymph node metastases were identified by PET in 4 of 14 patients who had lymph node involvement. CT had a similar sensitivity for detection of lymph node metastases. PET was superior to CT in identifying metastases to the liver — 7 of 8 patients had documented hepatic metastases detected by PET and only in 3 patients were these metastases detected by CT. Filmont and colleagues at UCLA evaluated the impact of FDG-PET imaging on the clinical stage determined by conventional imaging in the restaging of patients with colorectal cancer. In a population of 127 patients undergoing studies for restaging, PET downstaged 15 patients (12%), upstaged 18 patients (14%), and assigned the same stage in 94 patients (74%) compared with conventional imaging. Thus, whole-body FDG-PET had an impact on the clinical stage in 26% of colorectal cancer patients being restaged after treatment. The same group evaluated the prognostic value of FDG-PET in patients being restaged for colorectal cancer, comparing the prognostic value of FDG-PET and conventional imaging. The mean duration of follow-up was 61 +/- 29 weeks. Nine (16%) of the 55 patients had no evidence for residual/recurrent disease, whereas 46 (84%) had evidence for residual/recurrent disease. The positive and negative predictive values for PET were 95% and 59%, respectively. Conventional imaging had a positive predictive value of 89% and negative predictive value of 29%. The prognostic accuracy of PET was superior to that of conventional imaging (87% vs 71%). These data demonstrate that whole-body PET imaging predicts the outcome of colorectal cancer patients with high accuracy, and the high negative predictive value is superior to that of conventional imaging.

However, the real question is if it can supplant CT with contrast and that is not resolved.

NCCN on p.COL-2 says that PET/CT should not routinely be done for staging and should only be used to clarify an equivocal finding on a contrast enchanced CT. It recommends Chest/abdominal/pelvic CT annually for upto 5 y for patients at high risk forrecurrence.

The field is definitely moving toward accepting PET in various situation in colon cancer but not universally.

NCCN 2014 on p. COL-3 and REC-3 says that PET is not routinely recommended for surveillance. NCCN in its guideline on p. COL-3says that use of PET for restaging is not recommended.

Filmont JE, Vranjesevic D, Meta J, et al. Restaging of colorectal cancer patients: impact of FDG-PET on clinical stage by conventional imaging. Program and abstracts of the Society of Nuclear Medicine 48th Annual Meeting; June 23-27, 2001; Toronto, Ontario, Canada. J Nucl Med. 2001;42(suppl):123P. Abstract 461.

Filmont J, Vranjesevic D, Meta J, et al: Prognostic value of FDG-PET for predicting the outcome of re-staged colorectal cancer patients. Program and abstracts of the Society of Nuclear Medicine 48th Annual Meeting; June 23-27, 2001; Toronto, Ontario, Canada. J Nucl Med. 2001;42(suppl):124P. Abstract 464.

Abdel-Nabi H, Doerr RJ, Lamonica DM, et al. Staging of primary colorectal carcinomas with fluorine-18 fluorodeoxyglucose whole-body PET: correlation with histopathologic and CT findings. Radiology, 1998;206:755-760.

Podoloff DA, Advani RH, Allred C, Benson AB 3rd, Brown E, Burstein HJ, Carlson RW, Coleman RE, Czuczman MS, Delbeke D, Edge SB, Ettinger DS, Grannis FW Jr, Hillner BE, Hoffman JM, Kiel K, Komaki R, Larson SM, Mankoff DA, Rosenzweig KE, Skibber JM, Yahalom J, Yu JM, Zelenetz AD.NCCN task force report: positron emission tomography (PET)/computed tomography (CT) scanning in cancer.J Natl Compr Canc Netw. 2007 May;5 Suppl 1:S1-S22; quiz S23-2.