The role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the primary staging of rectal cancer

Abstract

BackgroundIn this study we aimed to determine the need for 18F-flourodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the preoperative staging of rectal carcinoma in our large patient group according to level and location of tumor.MethodTotally, 97 patients diagnosed with primary rectal adenocarcinoma between May 2009 and July 2011 were included in the study. Preoperative staging was performed by evaluating contrast-enhanced thoracic, abdominal, and pelvic computed tomographies. After staging by conventional methods, all patients underwent an 18F-FDG PET/CT. In all cases, the relationship between 18F-FDG uptake and gender, tumor height at the anal canal, localization in the rectal wall, plasma carcinoembryonic antigen levels, histopathological tumor type, and tumor stage were examined.ResultsWhile the ceCT was normal in 4 (4%) patients, it was positive for the rectum in 93 (95%), pelvic lymph nodes in 22 (22%), and distant metastases in 14 (14%) (liver (8), lung (8), bone (2), distant lymph nodes (6), and uterus (1)). Using computed tomography, disease stages were determined as stage 0, 1, 2, 3, and 4 in 4, 8, 48, 23, and 14 patients, respectively; 18F-FDG PET/CT was normal in two (2%) patients. The mean SUVmax of FDG-positive rectal tumors was calculated as 17.31 ± 9.37. Additionally, 18F-FDG uptake was seen in pelvic lymph nodes in 15 (15%) patients and in distant organs in 24 (24%) patients (liver (9), lung (12), bone (5), distant lymph nodes (11), uterus (1), and sigmoid colon (1)). According to an 18F-FDG PET/CT, 2, 7, 47, 20, and 21 patients were staged as stage 0, 1, 2, 3, and 4, respectively. In 14 patients (14.4%), the stage of the disease was either changed, and there was a need to make adjustments to the patient’s treatment strategy (n = 10), or the type of operation was changed (n = 4). In seven patients (0.7%), findings from 18F-FDG PET/CT images did not require any changes of the treatment plan.ConclusionF-FDG PET/CT provides new findings in addition to conventional techniques in the staging of primary rectal cancer. These findings could change the patients’ treatment strategies.

Impact of Fluorine-18 2-Fluoro-2-Deoxy-<smlcap>D</smlcap>-Glucose Uptake on Preoperative Positron Emission Tomography/Computed Tomography in the Lymph Nodes of Patients with Primary Colorectal Cancer

“…We assumed that ceCT could provide information about the enlargement of regional LNs; however, they have limited value during the evaluation of regional LN involvement because a normal-sized LN may have a tumor, and an enlarged LN may be reactive [21] .…”

“…LNs with increased F-18-FDG accumulation relative to surrounding soft tissues were considered metastatic, independent of their sizes. On ceCT imaging, a metastatic LN was defined as a lesion with short-axis diameter above 10 mm [21] . When there was a discrepancy between the interpreters' judge, a consensus was reached by discussion.…”

Validity of FDG PET/CT in patients presenting with primary colonic symptoms

“…Studies have reported a wide range of CRC tumors detection 20 to 90%. There are many factors that contribute in this discrepancy, such as using of different screening protocols, gold standards, variable inclusion criteria, different time gap between the imaging tools, and the variability between the images readers [7][8][9].…”

Predicting the risk of lymph node metastasis in early rectal cancer

“…(22) This resulted in changes in treatment strategy or operation performed. Although PET-CT may not be sufficient in identifying N stage for rectal cancer, the utility of routine PET-CT for overall staging deserves further study.…”