Koya Nakatani

The potential clinical value of FDG-PET for recurrent renal cell carcinoma

PURPOSE The clinical value of positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) for follow-up or suspected recurrence of renal cell carcinoma (RCC) has not been fully evaluated. The purpose of this study was to assess the diagnostic performance of FDG-PET for postoperative assessment in patients with RCC. METHODS We reviewed 28 scans in 23 patients who had undergone FDG-PET scans after surgery for RCC. Diagnostic accuracy of visually interpreted PET was evaluated based on final diagnoses obtained histologically or by clinical follow-up at least 6 months. Also, additional information over CT, influence on treatment decisions, and the accuracy of FDG uptake as a predictor of survival were assessed. RESULTS Recurrence of renal carcinoma was histologically (n=15) or clinically (n=6) confirmed in 21 of 28 cases. Overall, the sensitivity, specificity, and diagnostic accuracy using FDG-PET were 81%, 71%, and 79%, respectively. In papillary RCC, the sensitivity was 100%; however, that was 75% in clear cell RCC in patient-basis. PET correctly detected local recurrence and metastases in all cases in the peritoneum, bone, muscle and adrenal gland. Additional information was obtained from scans in 6 cases (21%), which influenced therapeutic management in 3 cases (11%). Cumulative survival rates over 5 years in the PET-positive vs. the PET-negative group were 46% vs. 83%, respectively (p=0.17). CONCLUSIONS FDG-PET would be useful for postoperative surveillance in patients with RCC, although its impact on treatment decisions may be limited. Further investigations are necessary to conclude whether PET has a prognostic value.

Diffuse homogeneous bone marrow uptake of FDG in patients with acute lymphoblastic leukemia.

PET (positron emission tomography) using FDG (¹⁸F-fluorodeoxyglucose) has been widely used in the evaluation of various malignancies, but its clinical application to leukemia remains limited. We report a case of leukemia in which diffuse bone marrow uptake of FDG was observed, and bone marrow aspiration subsequently revealed acute lymphoblastic leukemia. It is not easy to differentiate between physiological and pathologic uptake when diffuse homogeneous uptake in bone marrow is observed.

18F-FDG uptake in intraductal tubulopapillary neoplasm of the pancreas.

We report a 74-year-old man with intraductal tubulopapillary neoplasm (ITPN), a rare primary intraductal neoplasm of the pancreas. Focal intense uptake of 18F-FDG was seen on the initial PET, corresponding to a pancreatic mass. Although the patient had no treatment, the uptake was mild to moderate on a second PET performed about 1 month later. The tumor was resected, with the final diagnosis of ITPN with an associated invasive carcinoma. Clinicians should be aware that decreased uptake of FDG during the follow-up period without treatment can occur even in malignant tumors.

Roles and limitations of FDG PET in pediatric non-Hodgkin lymphoma

Purpose The usefulness of 18F fluorodeoxyglucose (FDG) positron emission tomography (PET) in pediatric Hodgkin lymphoma (p-HL) has been well demonstrated; however, pediatric non-Hodgkin lymphoma (p-NHL) has distinct characteristics from p-HL and adult NHL. We assessed roles of FDG PET in p-NHL. Materials and Methods Nineteen patients with p-NHL underwent 80 scans. Scans for staging (group A, n = 6) and response assessment (group B, n = 42) were compared with conventional imaging modalities (CIMs). Scans within group B for end-chemotherapy assessment (subgroup B+, n = 11) and for post-therapeutic surveillance (group C, n = 32) were analyzed for diagnostic performance. Results In group A, PET and CIM demonstrated comparable results. In group B, PET diagnoses were concordant with CIM in 21 and discordant in 11 studies. Of the discordant cases, PET suggested remnant lesions in 5 cases, whereas CIM suggested lesions in 6 cases. PET modified therapeutic strategy in 4 cases by detecting new extranodal lesions. In subgroup B+, sensitivity, specificity, and accuracy for predicting relapse were 50%, 71%, and 64%, respectively. In group C, sensitivity, specificity, and accuracy were 100%, 87%, and 88%, respectively, but positive predictive value was 33%. Conclusions The role of FDG PET in p-NHL may be limited, unlike with p-HL or adult NHL. Nevertheless, FDG PET may serve complementarily in detecting unexpected lesions that can emerge in p-NHL.

Clinical, Morphologic, and Pathologic Features Associated With Increased FDG Uptake in Schwannoma

OBJECTIVE The objective of this study was to investigate the clinical, morphologic, and pathologic features associated with increased 18F-FDG uptake in benign schwannomas. MATERIALS AND METHODS Twenty-two schwannomas in 22 patients (age range, 25-81 years) who had FDG PET or PET/CT scans and subsequently underwent surgical re-section were retrospectively analyzed. The maximum standardized uptake value (SUVmax) was compared with patient age, sex, tumor location (gastrointestinal vs nongastrointestinal origin), tumor size, gross appearance, intratumoral cellularity, intratumoral infiltration of inflammatory cells, presence of peritumoral lymphoid cuffs, and expression status of glucose transporters 1 and 3 on tumor cells. RESULTS The SUVmax of schwannomas ranged from 1.5 to 17.3 (median, 3.7). Significantly higher SUVmax was observed in gastrointestinal schwannomas (n = 4) compared with nongastrointestinal schwannomas (n = 18, p = 0.007) and in schwannomas with peritumoral lymphoid cuffs (n = 5) compared with those without peritumoral lymphoid cuffs (n = 17, p = 0.001). A significant correlation was seen between tumor location and the presence of peritumoral lymphoid cuffs (p < 0.001). Age, sex, tumor size, gross appearance, intratumoral cellularity, intratumoral inflammatory cell infiltration, and expression status of glucose transporters 1 and 3 on tumor cells had no significant correlation with SUVmax. CONCLUSION Gastrointestinal schwannomas and schwannomas with peritumoral lymphoid cuffs may be associated with elevated FDG uptake. Knowledge of the features of schwannomas associated with increased uptake may be helpful to avoid misinterpretation of benign schwannomas as malignancy.

Unilateral physiological FDG uptake in teres minor muscle seems well associated with IV tracer injection procedures.

FDG uptake in teres minor (TM) muscle is often physiologically observed. Here we reviewed data of 578 consecutive patients; TM uptake was observed in 138 patients-in 2 of 68 patients who were administered with FDG via a preexisting line and in 136 of 510 after on-site puncture. In 126 patients with TM uptake without unsuccessful on-site puncture, 78% of TM uptake sites were on the ipsilateral side of injection, 8% on the contralateral side, and 14% on both sides; Cohen κ coefficient was 0.815 when confined to unilateral uptake. Therefore, TM uptake seems well associated with tracer injection procedures.

Risk factors for extensive skeletal muscle uptake in oncologic FDG-PET/CT for patients undergoing a 4-h fast.

Objectives Postprandial insulin secretion causes extensive skeletal muscle accumulation (ESMA) of fluorine-18 fluorodeoxyglucose (FDG), which adversely affects visual interpretation of FDG-PET/CT. We investigated factors related to ESMA despite a fast of at least 4 h. Methods A total of 3595 patients underwent FDG-PET/CT following a fast for at least 4 h. Among them, patients exhibiting ESMA affected by postprandial insulin and sex-matched and age-matched individuals without ESMA as controls were analysed. The following factors were compared: BMI, plasma glucose, presence of diabetes including suspected diabetes (DM-IS), presence of diabetes excluding suspected diabetes, insulin therapy, approximate volume of gastric food residue estimated by CT and residue including water. Multivariate analysis was performed among cases and controls made to fast identically for 4–5 h to assess independent risk factors. Results Overall, 44 patients with ESMA and 100 controls were identified. The BMI of cases (22.0±3.0) was not significantly different from that of controls (21.5±2.9). Plasma glucose was significantly higher in cases (134.9±44.0 vs. 113.6±31.4 mg/dl; P=0.0050). Cases had a significantly higher proportion of DM-IS, presence of diabetes excluding suspected diabetes, insulin therapy, gastric food residue and residue including water (P<0.0001, P=0.0074, 0.0011, 0.0008 and 0.039, respectively). Logistic regression analysis among 29 cases and 100 controls who had undergone 4–5 h fasting revealed that DM-IS and gastric food residue were independent risk factors for ESMA with odds ratios of 5.14 (P=0.0006) and 5.39 (P=0.0014), respectively. Conclusion It would be preferable to fast for a longer time, especially for patients with glucose intolerance, and avoid heavy meals to reduce gastric residue.

Radiological Evaluation of Response and Resistance of Ibritumomab

Radiolabeled anti-CD20 monoclonal antibody, 90Y-ibritumomab tiuxetan became available for the treatment of refractory or relapsed low-grade B-cell non-Hodgkin’s lymphoma (NHL). Although FDG-PET is widely used for monitoring the response to chemotherapy and radiotherapy, there are limited data for monitoring the response of NHL to radioimmunotherapy (RIT) with FDG-PET.