title: FDG avidity and PET/CT patterns in primary gastric lymphoma.
abstract: OBJECTIVE
  The use of 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in primary gastric lymphoma (PGL) is challenging due to physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. This study assesses FDG avidity and PET/CT patterns in newly diagnosed PGL.
  
  
  METHODS
  Sixty-two PET/CT studies of newly diagnosed PGL were reviewed (24 low-grade mucosa-associated lymphoid tissue [MALT], 38 aggressive non-Hodgkin's lymphoma [AGNHL]). FDG avidity, patterns (focal/diffuse), and intensity (visually vs. the liver and SUVmax) were assessed and compared to 27 controls. Gastric CT abnormalities and extragastric sites were recorded.
  
  
  RESULTS
  Gastric FDG uptake was found in 55/62 (89%) PGL (71% MALT vs. 100% AGNHL, p < 0.001) and 63% controls. A diffuse pattern was found in 60% PGL (76% MALT vs. 53% AGNHL, p = NS) and 47% controls. FDG uptake higher than liver was found in 82% PGL (58% MALT vs. 97% AGNHL, p < 0.05) and 63% controls. SUVmax in FDG-avid PGLs was 15.3 +/- 11.7 (5.4 +/- 2.9 MALT vs. 19.7 +/- 11.5 AGNHL, p < 0.001) and 4.6 +/- 1.4 in controls. CT abnormalities were found in 79% PGL (thickening, n = 49; ulcerations, n = 22). Extra-gastric FDG-avid sites were seen in none of MALT, but 61% of AGNHL (nodal, n = 18; nodal and extranodal, n = 5).
  
  
  CONCLUSIONS
  FDG avidity was present in 89% of PGLs, including all patients with AGNHL but only 71% of MALT. FDG uptake can be differentiated, in particular in AGNHL-PGL, from physiologic tracer activity by intensity but not by pattern. Extragastric foci on PET and structural CT abnormalities are additional parameters that can improve PET/CT assessment of PGL. Defining FDG avidity and PET/CT patterns in AGNHL and a subgroup of MALT-PGL before treatment may be important for further monitoring therapy response.
authors.affiliation: Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Lea
authors.initials: L
authors.lastname: Radan
authors.forename: Doron
authors.initials: D
authors.lastname: Fischer
authors.forename: Rachel
authors.initials: R
authors.lastname: Bar-Shalom
authors.forename: Eldad J
authors.initials: EJ
authors.lastname: Dann
authors.forename: Ron
authors.initials: R
authors.lastname: Epelbaum
authors.forename: Nissim
authors.initials: N
authors.lastname: Haim
authors.forename: Diana
authors.initials: D
authors.lastname: Gaitini
authors.forename: Ora
authors.initials: O
authors.lastname: Israel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008223:Lymphoma / Q000175:diagnosis* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D013274:Stomach Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18