Incremental diagnostic utility of gastric distension FDG PET/CT.
OBJECTIVE
To assess the diagnostic utility of gastric distension (GD) FDG PET/CT in both patients with known gastric malignancy and those not known to have gastric malignancy but with incidental focal FDG uptake in the stomach.


METHODS
This retrospective analysis included 88 patients who underwent FDG PET/CT following GD with hyoscine N-butylbromide (Buscopan®) and water ingestion as part of routine clinical evaluation between 2004 and 2014. FDG PET/CT scans before and after GD were reported blinded to the patient clinical details in 49 patients undergoing pretreatment staging of gastric malignancy and 39 patients who underwent GD following incidental suspicious gastric uptake. The PET findings were validated by a composite clinical standard.


RESULTS
In the 49 patients undergoing pretreatment staging of gastric malignancy, GD improved PET detection of the primary tumour (from 80 % to 90 %). PET evaluation of tumour extent was concordant with endoscopic/surgical reports in 31 % (interpreter 1) and 45 % (interpreter 2) using pre-GD images and 73 % and 76 % using GD images. Interobserver agreement also improved with GD (κ = 0.29 to 0.69). Metabolic and morphological quantitative analysis demonstrated a major impact of GD in normal gastric wall but no significant effect in tumour, except a minor increase in SUV related to a delayed acquisition time. The tumour to normal stomach SUVmax ratio increased from 3.8 ± 2.9 to 9.2 ± 8.6 (mean ± SD) with GD (p < 0.0001), facilitating detection and improved assessment of the primary tumour. In 25 (64 %) of the 39 patients with incidental suspicious gastric uptake, acquisition after GD correctly excluded a malignant process. In 10 (71 %) of the remaining 14 patients with persistent suspicious FDG uptake despite GD, malignancy was confirmed and in 3 (21 %) an active but benign pathology was diagnosed.


CONCLUSIONS
GD is a simple way to improve local staging with FDG PET in patients with gastric malignancy. In the setting of incidental suspicious gastric uptake, GD is also an effective tool for ruling out malignancy and leads to the avoidance of unnecessary endoscopy.
Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, East Melbourne, Australia. pierre-yves.leroux@chu-brest.fr.|Department of Nuclear Medicine, Brest University Hospital, EA3878 (GETBO) IFR 148, Brest, France. pierre-yves.leroux@chu-brest.fr.
Pierre-Yves
PY
Le Roux
Department of Surgical Oncology, Peter MacCallum Cancer Centre, 7 St. Andrews Place, East Melbourne, VIC, 3002, Australia.
Cuong P
CP
Duong
Department of Surgical Oncology, Peter MacCallum Cancer Centre, 7 St. Andrews Place, East Melbourne, VIC, 3002, Australia.
Carlos S
CS
Cabalag
Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, East Melbourne, Australia.
Bimal K
BK
Parameswaran
Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, East Melbourne, Australia.
Jason
J
Callahan
Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, East Melbourne, Australia.|The University of Melbourne, Parkville, Australia.
Rodney J
RJ
Hicks
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
FDG PET/CT; Gastric cancer; Gastric distension; Incidental finding; Staging