Early interim FDG PET/CT prediction of treatment response and prognosis in pediatric Hodgkin disease-added value of low-dose CT.

BACKGROUND: Interim 18F-FDG PET helps predict outcome and tailor treatment in adults with Hodgkin disease (HD). OBJECTIVE: The purpose of this study was to assess predictive values of interim 18F-FDG PET/CT in children with HD and to define the potential added value to interim PET of low-dose CT. MATERIALS AND METHODS: Children were prospectively enrolled August 2002-April 2007. PET/low-dose CT was performed at staging, after 2 cycles, at the end of treatment and during follow-up (mean 45 months). Treatment was unchanged regardless of interim results. PET and low-dose CT were read independently. RESULTS: Of 34 enrolled children (ages 3-17 years), 27 achieved complete response, 4 had progressive disease and 3 had relapse. Interim PET alone had positive and negative predictive values of 67% and 89%, respectively. Interim low-dose CT alone had positive and negative predictive values of 35% and 100%, respectively. Interim PET/CT had positive and negative predictive values of 75% and 96%, respectively. CONCLUSIONS: Early interim PET/CT was a good predictor of outcome. Integrated PET and low-dose CT improved the predictive value in children with HD.

The Bnai Zion Planar Method: a simplified technique for the quantitation of the absolute renal uptake of (99m)Tc-DMSA in children.

AIM AND PURPOSE: Radionuclide imaging of the kidneys using dimercaptosuccinic acid chelate labeled with technetium-99m (Tc-DMSA) is a well-established method for evaluating the extent of kidney parenchymal involvement in the scenario of urinary tract infection and for the estimation of the functional renal mass. We have developed a simplified technique, Bnai Zion Planar Method (BZPM), to estimate absolute DMSA uptake by the kidneys, which uses a shorter time of acquisition and does not require cumbersome calculations of attenuation correction. The aim of this study was to validate this technique by comparing it with the Quantitative DMSA single-photon emission computed tomography (SPECT) (QDMSA) measurements as the reference method. METHODS: Sixty-one consecutive children (mean age 5.4+/-4.8 years) were included in the study. Absolute uptake of the radiopharmaceutical by the kidneys was measured using the QDMSA SPECT methods described earlier with data acquisition of 20 min. Kidney volumes and radioactivity concentration measurements were calculated on the reconstruction data using the threshold method. For the simplified technique (BZPM), a planar posterior view of the kidneys was acquired for 1 min at the end of the QDMSA SPECT study. RESULTS: In both kidneys we observed a significant strong correlation between the two methods. BZPM measurements were very similar to those obtained using the validated QDMSA method, as determined by linear regression analysis (Pearson's r=0.924, P<0.001), r(2)=0.854. The uptake according to QDMSA can be predicted by the uptake measured by the BZPM method using the following regression equation: QDMSA=0.445+1.061 BZPM. CONCLUSION: BZPM estimation in children using the newly proposed planar method was found to be nearly identical to the validated QDMSA SPECT method.

FDG avidity and PET/CT patterns in primary gastric lymphoma.

PURPOSE: 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.

The role of FDG-PET/CT in suspected recurrence of breast cancer.

BACKGROUND: Early diagnosis of recurrent breast cancer is crucial to selection of the most appropriate therapy. The current study evaluated the role of FDG-PET/CT in the assessment of suspected recurrent breast cancer in patients who presented with elevated serum tumor markers. METHODS: Forty-seven consecutive FDG-PET/CT studies of 46 women (aged 32-79 years; mean, 59.9 years) with a history of breast cancer presented with elevated serum tumor markers 1-21 years (mean = 6.2 years) after their initial diagnosis and were retrospectively evaluated. PET/CT results were confirmed by pathology (n = 11), further imaging, and follow-up (mean = 17.2 months; n = 36). Changes in further management based on PET/CT were recorded. RESULTS: Thirty (65%) patients had tumor recurrence, and 16 (35%) patients showed no further evidence of disease. Thirty-one patients had 32 abnormal PET/CT studies, and 15 patients had normal studies with an overall sensitivity, specificity, and accuracy of 90%, 71%, and 83%, respectively. In 37 patients, PET/CT was compared with contrast-enhanced CT and had a higher sensitivity (85% vs 70%), specificity (76% vs 47%), and accuracy (81% vs 59%). PET/CT had an impact on the management of 24 (5l%) patients. Of these, chemotherapy or radiotherapy was started in 16 patients, treatment was modified in 2 patients, and 6 patients were referred to biopsy, followed by referral to surgery for 2 patients. CONCLUSIONS: In patients with breast cancer and rising tumor markers, FDG-PET/CT had high performance indices and was superior to CT for diagnosis of tumor recurrence, which led to changes in the subsequent clinical management of 51% of these patients.