Incidental gastrointestinal 18F-Fluorodeoxyglucose uptake associated with lung cancer

The value of using fludeoxyglucose positron-emission tomography scan with respect to colorectal abnormalities-a cross-sectional study

Background

Fludeoxyglucose positron-emission tomography (FDG-PET) shows colic uptake regularly. Complementary colonoscopy is done. Aim: study the findings of colonoscopy.

Methods

All consecutive scans in 5 years were studied. Focal FDG uptake in colon and/or rectum were scored as + or ++. Clinical files and endoscopy reports were studied for final diagnosis.

Results

Focal FDG uptake was noted in 173 out of 2,075 scans (8.4%). Focal FDG activity was judged ++ in 73 patients (42.2%) and + in 100 (57.8%). The majority of colorectal cancers scored ++. Patients with ++ activity underwent or had undergone significantly more often a colonoscopy compared with patients with + activity, 82% versus 65% (P=0.02). FDG PET/CT was false positive with respect to polyp(s) or cancer in 13 cases (22%) of ++ FGD activity and in 38 cases of + FDG (P<0.001). In 25 patients a total of 69 polyps were not FDG avid.

Conclusions

FDG-PET scanning is a useful tool in oncology. However, false-positive and false-negative findings with respect to colonic uptake are present in a significant number of patients. If the clinical condition and the potential prognosis allows the performance of colonoscopy this procedure should be done.

PET/CT incidental detection of second tumor in patients investigated for pancreatic neoplasms

BACKGROUND

Positron Emission Tomography/computed tomography (PET/CT) is an imaging technique which has a role in the detection and staging malignancies (both in first diagnosis and follow-up). The finding of an unexpected region of FDG (Fluorodeoxyglucose) uptake can occur when performing whole-body FDG-PET, raising the possibility of a second primary tumor. The aim of this study was to evaluate our experience of second primary cancer incidentally discovered during PET/CT examination performed for pancreatic diseases, during the initial work-up or follow-up after surgical resection.

METHODS

In this study, a retrospective evaluation of a prospectively collected data base was performed. Three hundred ninety- nine patients with pancreatic pathology were evaluated by whole body PET/CT imaging from January 2004 to December 2014. Among them, 348 patients were scanned before surgical resection and 51 during the course of their follow-up (pancreatic cancer). Median follow-up time was 29 months (range 14-124).

RESULTS

Fifty-six patients (14%) had incidental uptake of FDG in their organs: 31 patients had focal uptake and 25 showed diffuse with or without focal uptake. All patients with focal uptake were investigated, and invasive malignancy was diagnosed in 22 patients: 14 colon, 4 lung, 1 larynx, 1 urothelial, 1 breast cancer, and 1 colon metastasis from pancreatic cancer. Twenty patients underwent resection, and 6 endoscopic removal of colonic polyps. Three patients were not operated for advanced disease, and two patients did not show any pathology (PET/CT false positive). Of the 10 patients investigated for diffuse uptake, no malignancy was found; none of these patients developed a second cancer during the follow-up.

CONCLUSIONS

As in other malignancies, unexpected FDG uptake can occur in patients having PET/CT investigation for pancreatic diseases. Focal uptake is likely to be a malignancy and deserves further investigations, although the stage and the poor prognosis of primary pancreatic cancer should be kept in mind. Some selected patients may benefit from the aggressive treatment of incidental lesions and show survival benefit.