Raghava Kashyap

High FDG activity in focal fat necrosis: a pitfall in interpretation of posttreatment PET/CT in patients with non-Hodgkin lymphoma

PurposePET/CT has a major role in lymphoma imaging, but glycolytic activity in inflammatory processes can reduce specificity. In this study we evaluated restaging PET/CT findings in patients with non-Hodgkin lymphoma (NHL) and fat necrosis.MethodsWe identified 16 patients from 8,819 restaging FDG PET/CT scans with suspicion of or biopsy-proven fat necrosis on PET/CT.ResultsAll patients had NHL and demonstrated focal FDG-avid nodular change on CT with density higher than that of fat but lower than that of soft tissue. Histological confirmation was obtained in eight patients, with high GLUT-1 staining between necrotic tissue and organizing fat necrosis evident. Uptake resolved in four patients, and surveillance was continuing in four without relapse.ConclusionAlthough rare, identification of fat necrosis in patients with a solitary FDG-avid nodule after therapy is important and may lead to the avoidance of unnecessary interventions or treatment. Specific features on CT aid identification, whilst follow-up imaging can be helpful as the metabolic abnormality regresses with time.

Role of fluorodeoxyglucose positron emission tomography/computed tomography in diagnostic evaluation of carcinoma urinary bladder: comparison with computed tomography.

Bladder carcinoma is the most frequent tumor of the urinary tract and accounts 7% of all malignancies in men and 2% of all malignancies in women. This retrospective study was carried out to assess the diagnostic utility of F18-fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the imaging evaluation of bladder carcinoma. Seventy-seven consecutive patients diagnosed to have carcinoma urinary bladder referred for F18-FDG PET/CT were included in this study. Thirty-four patients were for initial staging after transurethral biopsy and remaining 43 patients were for restaging. All patients also underwent CT scan of the abdomen and pelvis. PET/CT findings were correlated with diagnostic CT scan and histopathological findings. In 30 of the 34 patients for initial staging, both PET/CT and CT confirmed the primary lesion in the bladder. Histopathology report was available in 23 patients. Lymph nodes FDG uptake reported to be metastatic in 10/23 patients while CT detected lymph node metastasis in 12 patients. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy have been calculated to be 87.5%, 80%, 70%, 92%, 82% for PET/CT and 66%, 57%, 50%, 72%, 60% for CT respectively. PET/CT detected metastatic disease in 8 patients whereas CT detected in 4 patients. Of the 43 patients for restaging, local recurrence was detected in 24 patients on both PET/CT and CT. Histopathology report was available in 17 patients. Sensitivity, specificity, PPV, NPV and accuracy were 85%, 60%, 60%, 85%, 70% for PET/CT and 80%, 50%, 40%, 85%, 58% for CT respectively. Nineteen patients were detected to have metastatic disease by PET/CT, whereas CT detected metastases in 11 patients. F-18 FDG PET/CT is a very useful modality in pre-operative staging and monitoring after surgery, chemotherapy or radiotherapy of patients with carcinoma urinary bladder.

Modifying the Poor Prognosis Associated with 18F-FDG–Avid NET with Peptide Receptor Chemo-Radionuclide Therapy (PRCRT)

TO THE EDITOR: Applying conventional diagnostic imaging paradigms, a negative 18F-FDG PET/CT study in a patient with biopsyproven metastatic neuroendocrine tumor (NET) would be considered false-negative. With molecular imaging, however, we have emerged from using imaging merely to detect and measure lesion size to increasingly using it to characterize disease phenotype, which was formerly the domain of pathology. We therefore read with interest the recent publication by Bahri et al. (1) confirming that in patients with metastatic NET, 18F-FDG PET/CT has powerful prognostic utility superior even to conventional pathologic factors such as histologic grade or Ki-67. These data substantiate earlier data by Binderup et al. (2) and Garin et al. (3). These findings highlight the ability of PET/CT to reproducibly characterize all sites of disease in a given patient, minimizing the sampling error inherent with histopathologic sampling of a random site of disease (4). In their prospective study, Bahri et al. (1) demonstrated a median overall survival of 15 mo for 18F-FDG–positive NET compared with 119.5 mo for 18F-FDG–negative NET. The authors also explored the additional value of somatostatin receptor imaging. In keeping with the concept that patient outcomes are related to the degree of tumor differentiation, patients with positive somatostatin receptor imaging results had a better prognosis than those without, but even so, 18FFDG also retained its prognostic utility within this group. The adverse prognosis associated with 18F-FDG avidity need not necessarily be the fate of such patients. We have recently published data regarding the efficacy of peptide receptor chemo-radionuclide chemoradiotherapy (PRCRT) with 177Lu-DOTATATE combined with 5-fluorouracil in a cohort of 52 patients with 18F-FDG-avid NET (5). Despite the anticipated poor prognosis of this cohort, we demonstrated an unexpectedly long progression-free survival of 48 mo, whereas median overall survival had not been reached at the time of publication. We have since updated the overall survival data of this cohort after a median follow-up of 58 mo, still with no patients lost to follow-up. Median overall survival from the commencement of PRCRTwas 55 mo (Kaplan–Meier survival analysis based on log-rank testing). In response to the data presented by Bahri et al., we have further performed subanalysis in patients with a maximum standardized uptake value of at least 4.5 (n5 44) or a tumorto normal-tissue ratio of at least 2.5 (n 5 23), groups defined to have a relative risk for death of 6.2 and 23, respectively. Median survival for these subgroups in our cohort was the same as for our overall group. These remarkable results attest to the superior efficacy of PRCRT compared with conventional therapeutic strategies, since we can assume that most patients in the study by Bahri et al. did not have access to this therapeutic modality because of lack of regulatory approval for PRRT in France, where the study was undertaken. Additionally, our results have a lead-time bias that is disadvantageous to our analysis, as survival in our study was not measured from diagnosis but rather from the time of PRCRT in a population that was previously treated with conventional therapeutic regimens, including at least one line of chemotherapy in 67%. Thus, our median survival of 55 mo is remarkable in comparison to the 15 mo defined by Bahri et al., suggesting that PRCRT prolongs survival by years in many patients with 18F-FDG–avid metastatic NET. In addition to the encouraging results for the cohort, 4 patients have no evidence of disease after a follow-up of 30–97 mo, indicating that a small proportion of patients can be cured. Two achieved a complete response with PRCRT alone, whereas the other two were rendered disease-free after surgery; one to excise the primary site after complete regression of metastatic disease, and another in whom an R0 resection of residual primary and metastatic disease was achieved after major disease regression (6). Importantly, the resected residual disease in both patients was of significantly lower grade than that documented before treatment. Furthermore, 27% of patients in our cohort ultimately achieved a complete metabolic response on 18F-FDG PET/CT despite the presence of residual disease on somatostatin receptor PET/CT. In these patients, it appears PRCRT is able to convert the disease from an aggressive to an indolent phenotype. PRCRT is remarkably well tolerated, as we and others have previously described (5,7,8). However, there is a risk of long-term toxicity. With longer follow-up in our cohort, there have been 2 cases of myelodysplasia, although both patients remain alive after 44 and 79 mo of follow-up. This risk must be weighed against the risk of death from the underlying NET and suggests that the risk–benefit ratio is likely to be highest for patients with higher grades of NET. Although the optimal sequences for available therapies remain uncertain, we believe that the most sensible approach is to use the most efficacious and least toxic therapy upfront. For metastatic 18F-FDG–avid ENETS (European Endocrine Tumor Society) grade 2 NET, our results recommend that PRCRT be the first-line therapeutic modality of choice, and we have recently changed our multidisciplinary neuroendocrine service guidelines to reflect this recommendation. There is further room to optimize delivery of PRCRT by refinement in patient selection and delivery of therapy (9), including the use of 90Y in patients with larger-volume disease and the use of newer chemotherapeutic combinations such as capecitabine and temozolomide for pancreatic NET (10). We are hopeful that these refinements will further improve patient outcomes.

Solitary sternal metastasis from hepatocellular carcinoma detected by F-18 FDG PET/CT

Fluorine-18 fluoro-deoxy-glucose positron emission tomography (F-18 FDG PET) is not sensitive modality for the diagnosis of primary hepatocellular carcinoma (HCC). However, FDG-PET imaging may be useful in the identification of extrahepatic metastases. We report an interesting image of HCC with solitary metastasis to sternum detected by F-18 FDG PET/CT.

(18)F-fluoride PET/CT in avascular necrosis of the femoral head.

Avascular necrosis (AVN) of the femoral head is a devastating disease in young adults. Magnetic resonance imaging is considered the most sensitive and specific technique in the diagnosis of this condition. The authors present an interesting image of bilateral AVN of the femoral heads diagnosed on F-fluoride positron emission tomography/computed tomography.

Left ventricular diastolic parameters in dilated cardiomypoathy: are we missing out on something?

Equilibrium radionuclide ventriculography is an established modality to assess the left ventricular (LV) systolic function in several clinical situations. Diastolic parameters can also be extracted from this investigation. The aim of our study is to assess the diastolic function of the left ventricle in cases of idiopathic dilated cardiomyopathy (IDCM) and ischemic cardiomyopathy, where systolic dysfunction has been considered of prime pathologic significance. We conducted a retrospective analysis of 89 patients who had undergone radionuclide ventriculography at our department with established diagnosis of IDCM in 59 patients and ischemic cardiomyopathy in remaining 30 patients. Peak filling rate (PFR) was assessed. The PFR was significantly lower in both patients with IDCM (median = 1.61 end diastolic volumes [EDV]/s) and ischemic cardiomyopathy (median = 2.005 EDV/s). 33% of the patients with ischemic cardiomyopathy and ejection fraction (EF) >45% had diastolic dysfunction while 25% of patients with IDCM and EF >45% had low PFR. Diastolic dysfunction can coexist in patients with dilated cardiomyopathy and even in patients with preserved LV EF. Routine evaluation of diastolic function in patients with heart failure can help in elucidation of pathogenesis and management of patients.

Rare involvement of thyroid cartilage and thyroid gland by multiple myeloma on 18F-Fluorodeoxyglucose positron emission tomography/computed tomography

Multiple myeloma commonly involves the skeleton. Extraosseous disease is sometimes noticed involving various organs. We present a very unusual site of myeloma involvement in the thyroid gland and thyroid cartilage.

Usefulness of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in dermatofibrosarcoma protuberans on treatment with imatinib

Dermatofibrosarcoma protuberans (DFSP) is a rare locally aggressive tumor with distant metastases being unusual. We present a case of metastatic DFSP treated with imatinib showing complete metabolic response to treatment.

F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in a Rare Case of Recurrent Malignant Mixed Mullerian Tumor

We report a case of 66-year-old female with previous history of histopathologically proven. Malignant mixed mullerain tumor of the uterus in whom positron emission tomography/computed tomography (CT) done for characterization of soft tissue lesion in pelvis noticed on CT, showed extensive recurrent disease in the pelvis with pulmonary metastases.

Metabolic signature of the lesions on F18-fluoro-deoxyglucose positron emission tomography: A clue to the underlying pathology

Increase in glycolytic pathway, forms one of the major adaptations in various cancer types. This can be imaged using 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG PET). The intensity of FDG avidity is an indirect marker of the grade of the tumor. We present a case where FDG PET demonstrated a known chondrosarcoma and two other incidental lesions. The intensity of avidity in each of the lesions was grossly incongruent from the chondrosarcoma and further investigation proved the lesions to be two distinct primary malignancies, pathologically different from the known chondrosarcoma. We present the case to highlight the fact that the grade of FDG avidity is a clue to the pathological nature of the lesion and should always be considered while interpreting PET images.