Absolute number of new lesions on <Superscript>18</Superscript>F-FDG PET/CT is more predictive of clinical response than SUV changes in metastatic melanoma patients receiving ipilimumab

Purpose

Evaluation of response to immunotherapy is a matter of debate. The aim of the present study was to evaluate the response of metastatic melanoma to treatment with ipilimumab by means of ¹⁸F-FDG PET/CT, using the patients’ clinical response as reference.

Methods

The final cohort included in the analyses consisted of 41 patients with metastatic melanoma who underwent ¹⁸F-FDG PET/CT before and after administration of ipilimumab. After determination of the best clinical response, the PET/CT scans were reviewed and a separate independent analysis was performed, based on the number and functional size of newly emerged ¹⁸F-FDG-avid lesions, as well as on the SUV changes after therapy.

Results

The median observation time of the patients after therapy was 21.4 months (range 6.3–41.9 months). Based on their clinical response, patients were dichotomized into those with clinical benefit (CB) and those without CB (No-CB). The CB group (31 patients) included those with stable disease, partial remission and complete remission, and the No-CB group (10 patients) included those with progressive disease. The application of a threshold of four newly emerged ¹⁸F-FDG-avid lesions on the posttherapy PET/CT scan led to a sensitivity (correctly predicting CB) of 84% and a specificity (correctly predicting No-CB) of 100%. This cut-off was lower for lesions with larger functional diameters (three new lesions larger than 1.0 cm and two new lesions larger than 1.5 cm). SUV changes after therapy did not correlate with clinical response. Based on these findings, we developed criteria for predicting clinical response to immunotherapy by means of ¹⁸F-FDG PET/CT (PET Response Evaluation Criteria for Immunotherapy, PERCIMT).

Conclusion

Our results show that a cut-off of four newly emerged ¹⁸F-FDG-avid lesions on posttherapy PET/CT gives a reliable indication of treatment failure in patients under ipilimumab treatment. Moreover, the functional size of the new lesions plays an important role in predicting the clinical response. Validation of these results in larger cohorts of patients is warranted.

     

Role of <Superscript>18</Superscript>F-FDG PET/CT in patients affected by Langerhans cell histiocytosis

Purpose

Langerhans cell histiocytosis (LCH) is a rare hematological disorder for which the utility of¹⁸F-FDG PET/CT is unclear. Our aim was to explore the metabolic features of LCH and the possible role of¹⁸F-FDG PET/CT in LCH evaluation.

Materials and methods

We found 17 patients with histologically proven LCH who underwent 17¹⁸F-FDG PET/CT scans for staging and 42 scans for restaging/follow-up purposes. PET/CT results were compared with those obtained from other conventional imaging modalities (bone scintigraphy, plain radiogram, computed tomography, magnetic resonance).

Results

¹⁸F-FDG PET/CT was positive in 15/17 patients, and it detected 36/37 lesions; all bone and extraskeletal lesions, except for a cecal lesion, were¹⁸F-FDG-avid. Only 1/4 of the patients with lung LCH had hypermetabolic lesions. The average SUV_max of the FDG-avid lesions was 7.3 ± 6.7, the average lesion-to-liver SUV_max ratio was 3.4 ± 2.5, and the average lesion-to-blood pool SUV_max ratio was 4 ± 3.2. In comparison to other imaging methods,¹⁸F-FDG PET/CT detected additional lesions or was able to evaluate treatment response earlier in 33/74 cases; it was confirmatory in 38/74 and detected fewer lesions in 3/74 (all three with lung LCH).

Conclusions

¹⁸F-FDG PET/CT seems to be useful for evaluating LCH when compared to conventional imaging, except in pulmonary cases. It can be used both for staging and restaging purposes.

     

Incidental focal <Superscript>18</Superscript>F-FDG uptake in the frontal process of the maxilla on PET/CT: prevalence and clinical significance

Objective

We investigated the prevalence and clinical significance of incidental focal ¹⁸F-FDG uptake in the frontal process of the maxilla, mimicking malignancy on PET/CT.

Methods

From a total of 32,834 patients who underwent ¹⁸F-FDG PET/CT, patients with focal uptake in the frontal process of the maxilla were selected by a database search. For those patients, medical records including relevant imaging studies were reviewed.

Results

Thirty-nine patients (0.12 %) demonstrated focal uptake on PET/CT. On CT of PET/CT, all lesions showed ground-glass attenuation with or without bony expansion, consistent with fibrous dysplasia. When comparing previous PET/CT, follow-up PET/CT, and CT, a significant difference in degree of ¹⁸F-FDG uptake was noted, with no associated change in the size of maxillary lesions. There were no patients who had symptoms or signs related to maxillary lesions during follow-up.

Conclusion

Focal ¹⁸F-FDG uptake in the frontal process of the maxilla is a rare, incidental, and persistent finding with variable uptake and can represent a benign condition.

     

Speeding up PET/MR for cancer staging of children and young adults

Objective

Combining ¹⁸F-FDG PET with whole-body MR for paediatric cancer staging is practically feasible if imaging protocols can be streamlined. We compared ¹⁸F-FDG PET/STIR with accelerated ¹⁸F-FDG PET/FSPGR for whole-body tumour imaging in children and young adults.

Methods

Thirty-three children and young adults (17.5?±?5.5 years, range 10–30) with malignant lymphoma or sarcoma underwent a ¹⁸F-FDG PET staging examination, followed by ferumoxytol-enhanced STIR and FSPGR whole-body MR. ¹⁸F-FDG PET scans were fused with MR data and the number and location of tumours on each integrated examination were determined. Histopathology and follow-up imaging served as standard of reference. The agreement of each MR sequence with the reference and whole-body imaging times were compared using Cohen’s kappa coefficient and Student’s t-test, respectively.

Results

Comparing ¹⁸F-FDG PET/FSPGR to ¹⁸F-FDG PET/STIR, sensitivities were 99.3 % for both, specificities were statistically equivalent, 99.8 versus 99.9 %, and the agreement with the reference based on Cohen’s kappa coefficient was also statistically equivalent, 0.989 versus 0.992. However, the total scan-time for accelerated FSPGR of 19.8?±?5.3 minutes was significantly shorter compared to 29.0?±?7.6 minutes for STIR (p?=?0.001).

Conclusion

F-FDG PET/FSPGR demonstrated equivalent sensitivities and specificities for cancer staging compared to ¹⁸F-FDG PET/STIR, but could be acquired with shorter acquisition time.

Key Points

? Breath-hold FSPGR sequences shorten the data acquisition time for whole-body MR and PET/MR.? Ferumoxytol provides long-lasting vascular contrast for whole-body MR and PET/MR.? ¹⁸ F-FDG PET/FSPGR data provided equal sensitivity and specificity for cancer staging compared to ¹⁸ F-FDG PET/STIR.

     

Diagnostic performance of <Superscript>18</Superscript>F-FDG PET/CT and whole-body MRI before and early after treatment of multiple myeloma: a prospective comparative study

Objective

To determine the diagnostic accuracy of WB-MRI and ¹⁸F-FDG PET/CT in detecting infiltration pattern, disease activity, and response to treatment in patients with multiple myeloma (MM).

Materials and methods

Fifty-six patients with confirmed MM were included in the present study for pre-treatment evaluation. Among these individuals, 22 patients were available for the post-treatment evaluation of response to therapy. All patients were imaged with both WB-MRI and ¹⁸F-FDG PET/CT. All radiographic findings of infiltration pattern, disease activity, and response to therapy were compared. The diagnostic performance of both modalities was estimated using bone marrow aspirate and biopsy as the reference test.

Results

For detection of active myelomatous tissue at diagnosis, WB-MRI achieved higher sensitivity (94%) than ¹⁸F-FDG PET/CT (75%) (p?=?0.0039), whereas both modalities achieved the same specificity (80%). For detection of residual myelomatous tissue after treatment, ¹⁸F-FDG PET/CT achieved higher specificity (86%) than WB-MRI (43%) (p?=?0.0081), whereas both modalities achieved the same sensitivity (75%).

Conclusion

WB-MRI is more sensitive than ¹⁸F-FDG PET/CT in the diagnosis of MM before treatment; however, ¹⁸F-FDG PET/CT is more specific than WB-MRI in detecting residual involvement in treated patients.

     

Defining optimal tracer activities in pediatric oncologic whole-body <Superscript>18</Superscript>F-FDG-PET/MRI

Purpose

To explore the feasibility of reducing administered tracer activities and to assess optimal activities for combined ¹⁸F-FDG-PET/MRI in pediatric oncology.

Methods

30 ¹⁸F-FDG-PET/MRI examinations were performed on 24 patients with known or suspected solid tumors (10 girls, 14 boys, age 12?±?5.6 [1–18] years; PET scan duration: 4 min per bed position). Low-activity PET images were retrospectively simulated from the originally acquired data sets using randomized undersampling of list mode data. PET data of different simulated administered activities (0.25–2.5 MBq/kg body weight) were reconstructed with or without point spread function (PSF) modeling. Mean and maximum standardized uptake values (SUV_mean and SUV_max) as well as SUV variation (SUV_var) were measured in physiologic organs and focal FDG-avid lesions. Detectability of organ structures and of focal ¹⁸F-FDG-avid lesions as well as the occurrence of false-positive PET lesions were assessed at different simulated tracer activities.

Results

Subjective image quality steadily declined with decreasing tracer activities. Compared to the originally acquired data sets, mean relative deviations of SUV_mean and SUV_max were below 5 % at ¹⁸F-FDG activities of 1.5 MBq/kg or higher. Over 95 % of anatomic structures and all pathologic focal lesions were detectable at 1.5 MBq/kg ¹⁸F-FDG. Detectability of anatomic structures and focal lesions was significantly improved using PSF. No false-positive focal lesions were observed at tracer activities of 1 MBq/kg ¹⁸F-FDG or higher. Administration of ¹⁸F-FDG activities of 1.5 MBq/kg is, thus, feasible without obvious diagnostic shortcomings, which is equivalent to a dose reduction of more than 50 % compared to current recommendations.

Conclusion

Significant reduction in administered ¹⁸F-FDG tracer activities is feasible in pediatric oncologic PET/MRI. Appropriate activities of ¹⁸F-FDG or other tracers for specific clinical questions have to be further established in selected patient populations.

     

Different predictive values of interim <Superscript>18</Superscript>F-FDG PET/CT in germinal center like and non-germinal center like diffuse large B-cell lymphoma

Purpose

Diffuse large B-cell lymphoma (DLBCL) is a pathologically heterogeneous disease with different prognoses according to its molecular profiles. Despite the broad usage of ¹⁸F-fluoro-2-dexoxy-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT), previous studies that have investigated the value of interim ¹⁸F-FDG PET/CT in DLBCL have given the controversial results. The purpose of this study was to evaluate the prognostic value of interim ¹⁸F-FDG PET/CT in DLBCL according to germinal center B cell-like (GCB) and non-GCB molecular profiling.

Methods

We enrolled 118 newly diagnosed DLBCL patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP). Interim ¹⁸F-FDG PET/CT scans performed after 2 or 3 cycles of R-CHOP treatment were evaluated based on the Lugano response criteria. Patients were grouped as GCB or non-GCB molecular subtypes according to immunohistochemistry results of CD10, BCL6, and MUM1, based on Hans’ algorithm.

Results

In total 118 DLBCL patients, 35 % were classified as GCB, and 65 % were classified as non-GCB. Interim PET/CT was negative in 70 %, and positive in 30 %. During the median follow-up period of 23 months, the positive interim ¹⁸F-FDG PET/CT group showed significantly inferior progression free survival (PFS) compared to the negative interim ¹⁸F-FDG PET/CT group (P = 0.0004) in entire patients. A subgroup analysis according to molecular profiling demonstrated significant difference of PFS between the positive and negative interim ¹⁸F-FDG PET groups in GCB subtype of DLBCL (P = 0.0001), but there was no significant difference of PFS between the positive and negative interim ¹⁸F-FDG PET groups in non-GCB subtype of DLBCL.

Conclusions

Interim ¹⁸F-FDG PET/CT scanning had a significant predictive value for disease progression in patients with the GCB subtype of DLBCL treated with R-CHOP, but not in those with the non-GCB subtype. Therefore, molecular profiles of DLBCL should be considered for interim ¹⁸F-FDG PET/CT practice.

     

Influence of <Superscript>18</Superscript>F-FDG PET/CT on therapy management in patients with stage III/IV malignant melanoma

Purpose

To evaluate the influence of ¹⁸F-FDG PET/CT in comparison to CT alone on treatment decisions in patients with advanced melanoma and to analyse the 5-year survival data in comparison to literature data.

Methods

Therapy management in 64 consecutive patients (primary staging n?=?52; surveillance n?=?12) with stage III/IV melanoma who underwent ¹⁸F-FDG PET/CT between 2004 and 2005 in our department was retrospectively analysed. Treatment decisions were made by two dermatooncologists for each patient twice, first based on the CT results and then based on the PET/CT results. Therapy changes based on the PET/CT results were classified as “major” (e.g. change from metastasectomy to systemic therapy) or “minor” (e.g. change from first to second line chemotherapy). The 5-year survival data of different patient cohorts were calculated.

Results

In the 52 patients in the primary staging group, the results of ¹⁸F-FDG PET/CT led to therapy change in 59 % and a major therapy change in 52 %. ¹⁸F-FDG PET/CT led to the avoidance of futile operations in 13 patients with suspicious lesions on CT that were deemed nontumorous on PET/CT. In the 12 patients in the surveillance group, the results of ¹⁸F-FDG PET/CT led to therapy change in 33 % and a major change in 17 %. The 5-year survival rates were 30 % in the entire cohort, 34 % in the primary staging group, and 17 % in the surveillance group. A significant overall survival benefit was observed in patients in whom ¹⁸F-FDG PET/CT excluded metastases or in whom metastases could be completely removed compared with patients who were not eligible for surgery (41 % vs. 10 %).

Conclusion

Primary staging of patients with stage III/IV melanoma should be performed with ¹⁸F-FDG PET/CT, leading to higher diagnostic accuracy and enabling individualized therapeutic management, especially optimal patient selection for metastasectomy. This strategy may extend long-term survival even in patients with advanced disease.

     

Development of a nomogram combining clinical staging with <Superscript>18</Superscript>F-FDG PET/CT image features in non-small-cell lung cancer stage I–III

Purpose

Our goal was to develop a nomogram by exploiting intratumour heterogeneity on CT and PET images from routine ¹⁸F-FDG PET/CT acquisitions to identify patients with the poorest prognosis.

Methods

This retrospective study included 116 patients with NSCLC stage I, II or III and with staging ¹⁸F-FDG PET/CT imaging. Primary tumour volumes were delineated using the FLAB algorithm and 3D Slicer? on PET and CT images, respectively. PET and CT heterogeneities were quantified using texture analysis. The reproducibility of the CT features was assessed on a separate test–retest dataset. The stratification power of the PET/CT features was evaluated using the Kaplan-Meier method and the log-rank test. The best standard metric (functional volume) was combined with the least redundant and most prognostic PET/CT heterogeneity features to build the nomogram.

Results

PET entropy and CT zone percentage had the highest complementary values with clinical stage and functional volume. The nomogram improved stratification amongst patients with stage II and III disease, allowing identification of patients with the poorest prognosis (clinical stage III, large tumour volume, high PET heterogeneity and low CT heterogeneity).

Conclusion

Intratumour heterogeneity quantified using textural features on both CT and PET images from routine staging ¹⁸F-FDG PET/CT acquisitions can be used to create a nomogram with higher stratification power than staging alone.

     

Influence of volumetric 4′-[methyl-<Superscript>11</Superscript>C]-thiothymidine PET/CT parameters for prediction of the clinical outcome of head and neck cancer patients

Objective

This prospective study compared the value of pretreatment 4′-[methyl-¹¹C]-thiothymidine (¹¹C-4DST) volumetric parameters and those of 2-deoxy-2-[18F] fluoro-d-glucose (¹⁸F-FDG) in predicting the clinical outcome in patients with head and neck squamous cell carcinoma (HNSCC).

Methods

Fifty patients with HNSCC underwent ¹¹C-4DST PET/CT and ¹⁸F-FDG PET/CT prior to anticancer therapy. ¹⁸F-FDG metabolic tumor volume (¹⁸F-FDG MTV) and total lesion glycolysis (TLG) were calculated from ¹⁸F-FDG PET, and ¹¹C-4DST MTV and total lesion proliferation (TLP) were calculated from ¹¹C-4DST PET. All parameters were measured for the primary lesion and metastatic lymph nodes. Associations between clinical factors and PET/CT parameters and prognostic value were analyzed.

Results

Receiver-operating characteristic analysis revealed that MTV, TLG, and TLP acquired from the primary lesion and metastatic lymph nodes were good parameters for predicting disease relapse and death. The area under the curves (AUCs) ranged from 0.63 to 0.71 for ¹⁸F-FDG PET/CT parameters. The AUCs of ¹¹C-4DST PET/CT parameters were larger than those of ¹⁸F-FDG (range 0.72–0.81). Univariate analysis revealed that individuals with tumors showing a high value for any PET/CT parameter were at a significantly increased risk of relapse. Upon multivariate analysis, ¹⁸F-FDG MTV, ¹¹C-4DST MTV and ¹¹C-4DST TLP were significant independent factors for relapse-free survival (P = 0.04, P = 0.0001 and P = 0.0005, respectively).

Conclusion

Pretreatment ¹¹C-4DST PET/CT volume-based parameters can provide important prognostic information about patients with HNSCC.

     

<Superscript>89</Superscript>Zr-trastuzumab PET supports clinical decision making in breast cancer patients,when HER2 status cannot be determined by standard work up

Background

Up-to-date information on human epidermal growth factor receptor 2 (HER2) status in breast cancer (BC) is important, as expression can vary during the course of the disease, necessitating anti-HER2 therapy adjustments. Repeat biopsies, however, are not always possible. In this feasibility trial we assessed whether ⁸⁹Zr-trastuzumab PET could support diagnostic understanding and aid clinical decision making, when HER2 status could not be determined by standard work up. Additionally, HER2 status on circulating tumour cells (CTCs) was assessed.

Patients and methods

⁸⁹Zr-trastuzumab PET was performed in patients if disease HER2 status remained unclear after standard work up (bone scan, ¹⁸F-FDG PET, CT and if feasible a biopsy). PET result and central pathologic revision of available tumour biopsies were reported to the referring physician. CTC HER2 status prior to PET was evaluated afterwards and therefore not reported. Diagnostic understanding and treatment decision questionnaires were completed by the referring physicians before, directly after and?≥?3 months after ⁸⁹Zr-trastuzumab PET.

Results

Twenty patients were enrolled: 8 with two primary cancers (HER2-positive and HER2-negative BC or BC and non-BC), 7 with metastases inaccessible for biopsy, 4 with prior HER2-positive and -negative metastases and 1 with primary BC with equivocal HER2 status. ⁸⁹Zr-trastuzumab PET was positive in 12 patients, negative in 7 and equivocal in 1 patient. In 15/20 patients, ⁸⁹Zr-trastuzumab PET supported treatment decision. The scan altered treatment of 8 patients, increased physicians’ confidence without affecting treatment in 10, and improved physicians’ disease understanding in 18 patients. In 10/20 patients CTCs were detected; 6/10 showed HER2 expression. CTC HER2 status was not correlated to ⁸⁹Zr-trastuzumab PET result or treatment decision.

Conclusion

⁸⁹Zr-trastuzumab PET supports clinical decision making when HER2 status cannot be determined by standard work up. The impact of CTC HER2 status needs to be further explored.

     

<Superscript>18</Superscript>F-FDG uptake by rectal cancer is similar in mucinous and nonmucinous histological subtypes

Purpose

PET/CT has been considered limited for the evaluation of mucinous colorectal tumors due to low ¹⁸F-FDG uptake. The aim of our study was to compare PET/CT variables in mucinous (MC) and nonmucinous (NMC) rectal adenocarcinomas.

Methods

Consecutive patients with cT2-4N0-2M0 rectal cancer included in a prospective clinical trial were reviewed. PET/CT was performed for primary baseline staging. Visual and quantitative analysis included SUVmax and SUVmean, metabolic tumor volume (MTV) and total lesion glycolysis (TLG). PET/CT parameters were compared according to histological subtypes.

Results

Overall, 73 patients were included (18 mucinous and 55 nonmucinous). SUVmax values were similar between MC and NMC (19.7 vs. 16.6; p = 0.5). MTV and TLG values were greater in the MC group (103.9 vs. 54.1; p = 0.007 and 892.5 vs. 358.8; p = 0.020) due to larger tumor volumes of MC.

Conclusions

Metabolic parameters at baseline PET/CT for patients with rectal cancer are similar in mucinous and nonmucinous histological subtypes.

     

Assessment of intratumor heterogeneity in mesenchymal uterine tumor by an <Superscript>18</Superscript>F-FDG PET/CT texture analysis

Objective

The aim of this study was to retrospectively evaluate the clinical significance of ¹⁸F-FDG PET/CT textural features for discriminating uterine sarcoma from leiomyoma.

Methods

Fifty-five patients with suspected uterine sarcoma based on ultrasound and MRI findings who underwent pretreatment ¹⁸F-FDG PET/CT were included. Fifteen patients were histopathologically proven to have uterine sarcoma, 14 patients by surgical operation and one by biopsy, and 40 patients were diagnosed with leiomyoma by surgical operation or in a follow-up for at least 2 years. A texture analysis was performed on PET/CT images from which second- and higher order textural features were extracted in addition to standardized uptake values (SUVs) and other first-order features. The accuracy of PET features for differentiating between uterine sarcoma and leiomyoma was evaluated using a receiver-operating-characteristic (ROC) analysis.

Results

The intratumor distribution of ¹⁸F-FDG was more heterogeneous in uterine sarcoma than in leiomyoma. Entropy, correlation, and uniformity calculated from normalized gray-level co-occurrence matrices and SUV standard deviation derived from histogram statistics showed greater area under the ROC curves (AUCs) than did maximum SUV for differentiating between sarcoma and leiomyoma. Entropy, as a single feature, yielded the greatest AUC of 0.974 and the optimal cut-off value of 2.85 for entropy provided 93% sensitivity, 90% specificity, and 92% accuracy. When combining conventional features with textural ones, maximum SUV (cutoff: 6.0) combined with entropy (2.85) and correlation (0.73) provided the best diagnostic performance (100% sensitivity, 94% specificity, and 95% accuracy).

Conclusions

In combination with the conventional histogram statistics and/or volumetric parameters, ¹⁸F-FDG PET/CT textural features reflecting intratumor metabolic heterogeneity are useful for differentiating between uterine sarcoma and leiomyoma.

     

<Superscript>18</Superscript>F-FDG PET/CT to differentiate malignant necrotic lymph node from benign cystic lesions in the neck

Objective

Patients presenting with cystic lesions in the neck without obvious signs of malignancy constitute a diagnostic challenge since fine needle aspiration is often insufficient and a diagnosis may not be reached until surgical resection/biopsy is performed. The differential diagnosis of a cystic cervical mass comprises a variety of benign conditions, but malignancy must be ruled out. We examined the diagnostic performance of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET/CT to identify malignancy.

Methods

We retrospectively included consecutive patients referred from the Department of ENT Head and Neck Surgery for ¹⁸F-FDG PET/CT-scans because of a solitary neck cyst. Scan results were compared to histopathology and follow-up.

Results

The study comprised 58 patients. Twenty patients (34%) were diagnosed with cancer during follow-up. PET/CT suggested malignancy in 34 patients (19 true positive, 15 false positive) and showed no malignancy in 24 (23 true negative, 1 false negative). The sensitivity, specificity, accuracy, positive and negative predictive values were 95% (76–99%), 61% (45–74%), 72% (60–82%), 56% (39–71%), and 96% (80–99%), respectively (95% confidence intervals in brackets). The primary tumor was identified in 14 out of the 20 patients with confirmed cancer. Increased metabolism, as evaluated by PET, was the only imaging characteristic among several others, which associated independently with malignancy in the cystic neck lesions, odds ratio 1.27 (1.07–1.50), p = 0.006.

Conclusion

¹⁸F-FDG PET/CT could reliably rule out malignancy (NPV 96%), albeit with a high frequency of false positive scans, requiring further diagnostic work-up. Increased metabolism was the best imaging parameter to differentiate between malignant and benign lesions.

     

Prognostic role of pretreatment 18F-FDG PET/CT in primary brain lymphoma

Objective

Primary brain lymphoma is an aggressive extranodal non-Hodgkin lymphoma with poor prognosis. Many possible prognostic factors are investigated with controversial results, but possible prognostic role of 18fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) features remains unclear. Our aim was to study the metabolic behavior of brain lymphoma at 18F-FDG PET/CT and the prognostic impact of qualitative and semiquantitative PET/CT parameters.

Methods

Between 2006 and 2018, 52 patients (26 females and 26 males; mean age: 61 years) with histologically confirmed diagnosis of brain lymphoma who underwent 18F-FDG PET/CT for staging before any treatment were included. PET images were qualitatively and semiquantitatively analyzed by measuring the maximum standardized uptake value body weight (SUVbw), lean body mass (SUVlbm), body surface area (SUVbsa), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). The Kaplan–Meier method was used to estimate the progression-free survival (PFS) and overall survival (OS) times. Cox regression models were performed to determinate the relation between qualitative and semiquantitative PET/CT features and OS and PFS.

Results

Thirty-nine patients had positive 18F-FDG PET/CT showing 18F-FDG uptake (mean SUVbw of 18.2; SUVlbm of 13.9; SUVbsa of 5; MTV of 14.8; TLG of 153) at the corresponding cerebral lesion; the remaining 13 were not 18F-FDG avid. Relapse or progression of disease occurred in 22 patients with an average time of 9.7 months; death occurred in 18 patients with an average of 7.9 months. There was no difference in PFS and OS between baseline PET/CT positive and negative groups or considering SUVbw, SUVlbm, and SUVbsa. PFS and OS was significantly shorter in patients with MTV ≥?9.8 cm³ (p?=?0.037 and p?=?0.022, respectively) and TLG ≥?94 (p?=?0.045 and p?=?0.0430, respectively).

Conclusions

18F-FDG avidity was noted in 75% of cases. Only metabolic tumor parameters (MTV and TLG) were independently correlated with PFS and OS.

     

Image fusion between 18F-FDG PET and MRI in cardiac sarcoidosis: A case series

Background

Sarcoidosis is a systemic disorder of unknown etiology. It is distinguished by the presence of noncaseating epithelioid granulomas. This study demonstrates the use of image fusion between (18)F-fluoro-2-deoxy-d-glucose positron emission tomography (18F-FDG PET) and magnetic resonance imaging (MRI) to diagnose patients with cardiac sarcoidosis (CS).

Methods

Seven patients diagnosed with sarcoidosis were retrospectively included. All patients underwent 18F-FDG PET/CT and cardiac MRI.

Results

On the MRI scan, late gadolinium enhancement (LGE) was observed in five patients. T2-weighted images revealed areas with an increased signal consistent with myocardial edema in two patients and with hypointensity suggesting fibrosis in one patient. Increased 18F-FDG uptake was seen in the myocardial wall in three patients, indicating active inflammation.

Conclusion

18F-FDG PET and MRI image fusion allows clinicians to obtain complete morphofunctional cartography in patients with sarcoidosis. Our data show that 18F-FDG PET/MRI image fusion imaging can be useful in the diagnosis of CS.

     

Is whole-body fluorine-18 fluorodeoxyglucose PET/CT plus additional pelvic images (oral hydration–voiding–refilling) useful for detecting recurrent bladder cancer?

Objective

Because of the urinary excretion of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG), FDG-PET or PET/CT is thought of little value in patients with bladder cancer. The purpose of our study was to investigate the value of ¹⁸F-FDG PET/CT with additional pelvic images in detection of recurrent bladder cancers.

Methods

From December 2006 to August 2010, 35 bladder cancer patients (median age 56 years old, ranging from 35 to 96) underwent routine ¹⁸F-FDG PET/CT. To better detect bladder lesions, a new method called as oral hydration–voiding–refilling was introduced, which included that all the patients firstly received oral hydration, then were required to void frequently and finally were demanded to hold back urine when the additional pelvic images were scanned. Lesions were confirmed by either histopathology or clinical follow-up for at least 6 months.

Results

Finally, 12 recurrent cases of 35 patients were confirmed by cystoscope. PET/CT correctly detected 11 of them. Among these 11 true positive patients, 5 patients (45.5 %) were detected only after additional pelvic images. Lichenoid lesions on the bladder wall were missed, which caused 1 false negative result. All three false positive cases were testified to be inflammatory tissues by cystoscope. Therefore, the sensitivity, specificity and accuracy of PET/CT were 91.7 % (11/12), 87.0 % (20/23) and 88.6 % (31/35), respectively.

Conclusion

PET/CT with additional pelvic images can highly detect recurrent lesions in residual bladder tissues. Our method with high accuracy and better endurance could be potentially applied.

     

Comparison of FDG PET/CT and MRI in lymph node staging of endometrial cancer

Objective

Endometrial cancer is the most frequent cancer occurring in the female genital tract in the Western countries. Because surgical staging is currently the standard, noninvasive techniques that accurately identify lymph node (LN) metastases would be beneficial by reducing costs and complications. The purpose of our study is to compare the diagnostic accuracy of 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) with that of magnetic resonance imaging (MRI) for detecting LN metastases in the preoperative staging of endometrial cancer.

Methods

Two hundred eighty-seven consecutive patients with endometrial cancer underwent preoperative PET/CT and MRI for staging. The malignancy criteria for LNs were a short diameter of 1 cm or more by MRI and focally increased ¹⁸F-FDG uptake by PET/CT. After evaluating PET/CT and MRI separately, morphologic and functional image findings were compared with the histological findings regarding LN metastasis for all patients. PET/CT and MRI images were classified on the basis of histological findings as true-positive, true-negative, false-positive, or false-negative. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated.

Results

Histologic examination revealed LN metastases in 51 patients (17.8 %). The maximal standardized uptake values (SUVmax) of the primary lesions by PET/CT ranged from 1.4 to 37.7, with a mean value of 9.3, whereas those of the metastatic LNs ranged from 2.0 to 22.5 with a mean of 7.3. On a per-patient basis, node staging resulted in sensitivities of 70.0 % with ¹⁸F-FDG PET/CT and 34.0 % with MRI, and specificities of 95.4 % with PET/CT and 95.0 % with MRI. The NPV of PET/CT was 94.3 %, and that of MRI was 87.2 %. On a lesion base analysis, sensitivity of PET/CT was 79.4 % while that of MRI was 51.6 %. In detecting distant metastasis, the sensitivity, specificity, accuracy, PPV, and NPV of PET/CT were 92.9, 98.9, 98.6, 81.3, and 99.6 %, respectively.

Conclusion

Diagnostic performance of FDG PET/CT was better than MRI for detecting metastatic lymph nodes in patients with endometrial cancer both by patient basis and lesion basis analyses. Due to high NPV, FDG PET-CT could aid in selecting candidates for lymphadenectomy.

     

Comparison of 18F-FDG-PET/CT and 18F-FDG-PET/MR imaging in oncology: a systematic review

Objective

The aim of this study was to systematically review the literature to evaluate the clinical performance of integrated ¹⁸F-FDG PET/MR as compared with ¹⁸F-FDG PET/CT in oncologic imaging.

Methods

The literature was searched using MEDLINE and EMBASE via OVID. Studies comparing the diagnostic accuracy of integrated ¹⁸F-FDG PET/MR and ¹⁸F-FDG PET/CT in the diagnosis, staging/restaging, assessment of treatment response, or evaluation of metastasis in patients with suspected or diagnosed cancers were deemed eligible for inclusion. Risk of bias and applicability concerns were assessed using the QUADAS-2 tool.

Results

Twenty studies met the inclusion criteria. The overall quality of the studies was rated favorably with bias or applicability concerns in a few studies. Our review suggests that ¹⁸F-FDG PET/MR performs comparably to ¹⁸F-FDG PET/CT in the detection of local lymph node and distant metastases and superiorly in determining the local extent of tumor. SUV obtained from ¹⁸F-FDG PET/MR correlated highly with those obtained from ¹⁸F-FDG PET/CT.

Conclusions

Based on early evidence, ¹⁸F-FDG PET/MR is comparable to ¹⁸F-FDG PET/CT in the clinical scenarios examined in this review. The potential for interchangeability of ¹⁸F-FDG PET/MR with ¹⁸F-FDG PET/CT will vary by indication and the body site that is being imaged, with PET scanners integrated with MRI predicted to provide greater detail in the evaluation of local tumor extent, where ¹⁸F-FDG PET/CT can be limited.

     

Residual FDG uptake of primary thyroid lymphoma after treatment may overestimate residual lymphoma

Objective

To assess ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) images in primary thyroid lymphoma (PTL) patients before and after treatment.

Methods

We conducted a retrospective review of data for ten patients (four men, six women) of mean age 65 (range 48–88) years, with histopathologically confirmed malignant thyroid lymphoma who underwent pre-treatment and post-treatment ¹⁸F-FDG PET between January 2005 and December 2014. Thyroid uptake was assessed by the 5-point scale score based on maximum intensity projection images.

Results

Four of the ten patients were judged to have a complete metabolic response (scores 1–3) and four to have a partial metabolic response (PMR; scores 4–5). Three of the four PMR patients had a good outcome with a treatment-free interval and overall survival of at least 53.0 months, although two of these three patients showed residual FDG uptake in the thyroid for more than 2 years after completion of treatment. Two of the ten patients were considered to have progressive metabolic disease.

Conclusions

In patients with PTL, residual FDG uptake in the thyroid after treatment that corresponds to a PMR may not always indicate a poor outcome.