Diagnosis and Evaluation of Treatment Response in Relapsing Polychondritis Using 18F-FDG PET/CT.

A 58-year-old man presenting with dyspnea, weight loss, and night sweating underwent 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) because of a suspicion of malignancy. 18F-FDG PET/CT demonstrated mild to moderate uptake on nasal, cricoid, and tracheobronchial tree cartilages and costovertebral junctions. The diagnosis was relapsing polychondritis, which is a rare multisystem disease characterized by inflammation of cartilage. In addition, subsequent 18F-FDG PET/CT after treatment showed complete metabolic response.

18F-FDG and 68Ga-FAPI-04 PET/CT Findings of a Rare Epithelial-myoepithelial Carcinoma Arising From Ex Pleomorphic Adenoma of Parotid.

Epithelial-myoepithelial carcinoma (EMC) is a rare low-grade salivary gland neoplasm. Distant metastasis is rare, and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has been used to determine the metastatic disease in EMC. 68Ga-fibroblast activation protein inhibitors (FAPI) PET/CT is a promising imaging modality for diagnostic and theognostic purposes in various malignancies. Comparison studies with 18F-FDG have investigated the role of 68Ga-FAPI PET/CT. Herein, we present 18F-FDG and 68Ga-FAPI-04 PET/CT findings of a 51-year-old woman with metastatic EMC arising from ex-pleomorphic adenoma of the parotid.

The Role of [18F]FDG PET/CT in the Characterization of Thymic Epithelial Tumors at Initial Stage.

Purpose: The aim of this study was to evaluate the potential role of [18F]FDG positron emission tomography/computed tomography (PET/CT) in the characterization of thymic epithelial tumors (TETs). Materials and Methods: A total of 73 patients who underwent preoperative [18F]FDG PET/CT were included in this study. Visual total score (VTS), maximum standard uptake values (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and heterogeneity index (HI) parameters were analyzed to investigate the prediction of histopathologic grade and advanced stage. Results: The cohort included 26 patients with low-grade thymoma (LGT), 36 patients with high-grade thymoma (HGT), and 11 patients with thymic carcinoma (TC). Ninety-one percent of TC had VTS >2, whereas 31% of LGT and 75% of HGT had VTS >2. SUVmax, MTV, and TLG were statistically significantly higher in the TC group than in both thymoma and HGT. Using the cutoff value of 7.25 for SUVmax, TC was differentiated from thymomas with 91% sensitivity and 74% specificity. TC had significantly lower HI values than thymomas. HI parameters showed good diagnostic ability to differentiate TC from thymoma and TC from HGT. SUVmax, MTV, and TLG were significantly higher in advanced-stage disease than in early-stage disease. Conclusions: Visual and quantitative parameters can reliably predict both advanced disease and the grade of primary tumor in TETs. Therefore, as a promising metabolic imaging method, [18F]FDG PET/CT makes important contributions to preoperative evaluation in routine clinical practice.

Influence of Early Versus Delayed Hepatic Artery Perfusion Scan on 90Y Selective Internal Radiation Therapy Planning.

Purpose: This study evaluated the effect of an increase in the time interval between hepatic intra-arterial injection of 99mTc-macroaggregated albumin (MAA) and hepatic artery perfusion scintigraphy (HAPS) on the lung shunt fraction (LSF) and perfused volume (PV) calculations in the treatment planning of selective internal radiation therapy (SIRT). Methods: The authors enrolled 51 HAPS sessions from 40 patients diagnosed with primary or metastatic liver malignancy. All patients underwent scan at the first and fourth hour after hepatic arterial injection of 99mTc-MAA. Based on single-photon emission computed tomography images, LSF values were measured from each patient's first and fourth hour images. PV1 and PV4 were also calculated based on three-dimensional images using 5% and 10% cutoff threshold values and compared with each other. Results: The authors found that the median of LSF4 was statistically significantly higher than LSF1 (3.05 vs. 4.14, p ≤ 0.01). There was no statistically significant difference between PV1 and PV4 on the 10% (p = 0.72) thresholds. Conclusions: LSF values can be overestimated in case of delayed HAPS, potentially leading to treatment cancellation due to incorrectly high results in patients who could benefit from SIRT. Threshold-based PV values do not significantly change over time; nevertheless, keeping the short interval time would be safer.

The role of [68 Ga]Ga-FAPI-04 PET/CT in renal cell carcinoma: a preliminary study.

PURPOSE: We aimed to investigate the role of [68 Ga]Ga-FAPI-04 PET/CT and uptake patterns of primary and metastatic lesions in patients with renal cell carcinoma (RCC). METHODS: Twenty patients with a suspicious lesion considered primary renal malignancy or a history of RCC were included in our study. Two patients were excluded from further analyses due to other confirmed malignancies. Six patients were newly diagnosed, while the indication of 12 patients was restaging. All patients underwent [68 Ga]Ga-FAPI-04 and [18F]F-FDG PET/CT. SUVmax and tumor-to-background ratio (TBR) of primary (n = 7) and local recurrent lesions (n = 6) and lymph node (n = 26), lung (n = 32), bone (n = 5), and other metastases (n = 14) were compared between the two tracers. RESULTS: We detected 90 lesions in 18 patients with varying FAPI and FDG uptake values on both PET/CT. The median TBR of FAPI-PET/CT of all lesions was higher than TBR of FDG-PET/CT with statistically significance (5.6 vs. 2.1, p < 0.001). In primary and recurrent lesions, the median SUVmax, TBR, and tumor volume on FAPI-PET/CT were higher than FDG-PET/CT. The median SUVmax of lung lesions on FAPI-PET/CT was statistical significantly higher than FDG-SUVmax (3.8 vs. 1.8, p = 0.02). The median of FAPI-SUVmax on primary lesions was lower in the early stage based on TNM compared to the advanced stage. FAPI-SUVmax in 49% of all lesions were SUVmax ≥ 6, and 13% were SUVmax ≥ 10. In patient-based analyses, seven patients (39%) had at least one lesion with FAPI-SUVmax ≥ 10; 12 patients (67%) had at least one lesion with FAPI-SUVmax ≥ 6. CONCLUSION: This study showed the potential utility of [68 Ga]Ga-FAPI-04 PET/CT showing promising results in RCC. We have presumed that FAPI-PET/CT may be performed for complementary imaging modality providing prognosis and possibility of theranostic application in selected patients.

FAPI-Negative FDG-Avid Metastatic Relapse of Breast Cancer on PET/CT.

ABSTRACT: A 69-year-old woman with breast cancer underwent 18 F-FDG PET/CT because of the increased CA-15-3 level. 18 F-FDG PET/CT showed multiple hypermetabolic lymph nodes (LNs) in the neck and mediastinum. The patient was also referred for 68 Ga-fibroblast activation protein inhibitor (FAPI) 04 PET/CT for further evaluation. However, 18 F-FDG-avid LNs were FAPI-negative on 68 Ga-FAPI-04 PET/CT. Supraclavicular LN biopsy confirmed the metastasis of breast cancer. Recent reports have focused on the potential of FAPI PET imaging in breast cancer; however, this case highlights that false-negative 68 Ga-FAPI-04-PET/CT findings should also be considered while evaluating metastatic spread.

Utility of 68 Ga-FAPI-04 PET/CT in Adenoid Cystic Carcinoma Compared With 18 F-FDG PET/CT : Two Case Reports.

ABSTRACT: 68 Ga-fibroblast activation protein inhibitor (FAPI) PET/CT is an emerging imaging modality with high sensitivity and high tumor-to-background ratio in various cancers including in the head and neck regions. The authors present 2 cases of adenoid cystic carcinoma who underwent 68 Ga-FAPI-04 and 18 F-FDG PET/CT. Locoregional recurrence has been detected more precisely in the first case with 68 Ga-FAPI-04. In the second case, 68 Ga-FAPI-04 outperformed 18 F-FDG in the number of lesions and demonstrated intense FAP uptake on widespread metastases, which could provide a treatment option as a theranostic concept. These cases highlight that 68 Ga-FAPI-04 PET/CT may be useful for detecting local recurrence and metastases and help select patients for radionuclide treatments targeting cancer-associated fibroblasts.

68 Ga-FAPI-04 PET/CT and 18 F-FDG PET/CT in Metastatic Papillary Renal Cell Cancer.

ABSTRACT: Papillary renal cell cancer is a rare malignancy with limited treatment options in the advanced stage of the disease. We present the case of a 62-year-old man with progressive left-sided papillary renal cell carcinoma who underwent 68 Ga-FAPI (fibroblast activated protein inhibitor)-04 and 18 F-FDG PET/CT imaging. 68 Ga-FAPI-04 PET/CT demonstrated variable FAP expression in all metastatic lesions detected by 18 F-FDG PET/CT, including multiple lymph nodes, bone, and thyroid. This case highlights that FAP-targeted imaging can be a promising modality for diagnostic and theranostic use in papillary renal cell carcinoma.

PSMA-Directed Imaging and Therapy of Salivary Gland Tumors: A Single-Center Retrospective Study.

We analyzed the diagnostic performance of prostate-specific membrane antigen (PSMA) PET/CT and the dosimetry, efficacy, and safety of 177Lu-PSMA-617 radioligand therapy (RLT) in salivary gland malignancies (SGMs). Methods: We identified 28 SGM patients with PSMA PET/CT from our database. CT and PSMA PET/CT images were evaluated separately by 3 masked readers in joint reading sessions. Pathologic findings were grouped into 6 TNM regions, and lesion-based disease extent was classified as no disease (n = 1, 4%), unifocal (n = 2, 7%), oligometastatic (n = 9, 32%), multifocal (n = 3, 11%), or disseminated (n = 13, 47%). For each region, the SUVmax of the lesion with the highest uptake was measured and the visual PSMA expression score was evaluated on a per-patient basis using PROMISE criteria. The association between PSMA expression and clinical and histopathologic markers was tested using the Student t test. Five patients underwent PSMA RLT with intratherapeutic dosimetry. Response was assessed using RECIST 1.1, and adverse events were graded according to version 5.0 of the Common Terminology Criteria for Adverse Events. Results: Compared with CT, PSMA PET/CT demonstrated additional metastatic lesions in 11 of 28 (39%) patients, leading to upstaging of TNM and lesion-based disease extent in 3 (11%) and 6 (21%) patients, respectively. PSMA PET/CT detected CT-occult local tumor, regional lymph nodes, nonregional lymph nodes, and bone metastases in 1 (4%), 4 (14%), 2 (7%), and 4 (14%) patients, respectively; no additional lesions were detected in the other predefined regions. PSMA expression level was higher than liver in 6 patients (25%). A significantly higher SUVmax was observed in male than female patients (15.8 vs. 8.5, P = 0.007) and in bone than lung lesions (14.2 vs. 6.4, P = 0.006). PSMA RLT was discontinued after 1 cycle in 3 of 5 patients because of insufficient tumor doses. No adverse events of grade 4 or higher occurred. Conclusion: In SGMs, PSMA PET/CT demonstrated a superior detection rate and led to upstaging in about one third of patients when compared with CT. The male sex and the presence of bone metastases were associated with significantly higher PSMA expression. PSMA RLT was well tolerated, but most patients did not have more than 1 cycle because of insufficient tumor doses.

Comparison of 2D planar and 3D volumetric methods for estimation of split renal function by 99mTc-DMSA scintigraphy.

PURPOSE: Split renal function (SRF) can be measured by using several methods in 99mTc-DMSA scintigraphy. Geometric mean (GM) based methods derived from planar images(2D) have been used for several years, besides; 3D-methods were also reported as an option for assessment of SRF. The purpose of this study to compare 2D and 3D methods for calculation of SRF in pediatric and adult patients. METHODS: We evaluated 212 patients, underwent both planar and SPECT 99mTc-DMSA scintigraphy.2D-SRFs were calculated by GM without background correction (SRFnobcg), GM with background correction in crescent formation from lower lateral borders (SRFcres), and GM with background correction in circumferential formation, including the whole kidney surroundings (SRFcirc). In 3D settings, SRF was measured with SPECT (SRFspect). Paired t-test was used to compare the mean SRFs of each group. Bland-Altman method was used as an agreement method for each method. Analyses were performed based on left kidney SRFs. RESULTS: In comparison of 2D and 3D methods, SRFspect was significantly different from SRFnobcg and SRFcres (p=<0.001) but not from SRFcirc (p = 0.155) in all patients. Similar results were found for patients with high creatinine level, SRFcirc and SRFspect were not significantly different (p = 0.317), while significant differences were found between SRFspect and SRFnobcg/SRFcres (p=<0.001).On the other hand, all 2D-methods showed statistical differences (p=<0.001-0.026) from 3D-method in pediatric patients. Bland-Altman-plot demonstrated that SRFcirc underestimated the poor functioning kidneys. CONCLUSION: SRFcirc can be used in measurement of SRF in adult patients with normal functioning kidneys in busy clinics. However, SRFspect provides more accurate results and suggested particularly for pediatric patients and poor functioning kidneys.

Bilateral Testicular Mass Presenting as a Rare Manifestation of Extramedullary Plasmacytoma on 18F-FDG PET/CT.

ABSTRACT: We present the case of a 48-year-old man diagnosed with metastatic Ewing sarcoma who was referred for 18F-FDG PET/CT for treatment response evaluation following chemoradiotherapy. The patient also had complaints of new-onset testicular swelling at the time of imaging. Although the metastatic bone disease showed a complete metabolic response to treatment, 18F-FDG PET/CT demonstrated significantly increased metabolic activity in bilateral testicular mass. Consequently, the patient underwent bilateral orchiectomy, and histopathologic examination revealed bilateral testicular plasmacytoma, a rare manifestation of extramedullary plasmacytoma.

225Ac-Prostate-Specific Membrane Antigen Therapy for Castration-Resistant Prostate Cancer: A Single-Center Experience.

PURPOSE: Prostate-specific membrane antigen (PSMA)-targeted therapies are among the current promising treatments. We present our preliminary results on the use of 225Ac-PSMA therapy in patients with metastatic castration-resistant prostate cancer as a single center. METHODS: Twelve advanced stage metastatic castration-resistant prostate cancer patients who received 225Ac-PSMA therapy were recruited in this retrospective study. Patients were treated with 225Ac-PSMA therapy every 8 weeks, and prostate-specific antigen (PSA) response was analyzed. Meanwhile, overall survival (OS) and progression-free survival (PFS) were estimated. Hematological and nonhematological adverse effects were recorded before and at 8 weeks after the last treatment cycle. RESULTS: In total, 25 cycles of 225Ac-PSMA were administered to 12 patients. The pretreatment median PSA level was 129 ng/mL. After the first cycle of therapy, any PSA response was observed in 9 of 12 patients, whereas 6 of them had biochemical response of >50%. Four of 12 patients reached the best PSA response after the first treatment cycle, whereas 3 patients after the second and 2 patients after the third cycle. The median PFS and OS were 4 and 10 months, respectively. For patients with any PSA response after the first cycle, OS was found to be higher despite without any statistical significance (10 vs 4 months; P = 0.301) when compared with the nonresponsive group. No significant difference was encountered in terms of adverse effect in the pretreatment and posttreatment era. CONCLUSIONS: Our preliminary results are encouraging, especially patients who had PSA response after the first cycle of 225Ac-PSMA therapy.

Complementary Role of 68Ga-Prostate-Specific Membrane Antigen and 18F-FDG PET/CT for Evaluation of Metastases and Treatment Response in Renal Cell Carcinoma.

ABSTRACT: We present a case of clear cell renal cell carcinoma, which demonstrates complementary FDG and prostate-specific membrane antigen (PSMA) uptake on metastases in PET/CT, as an example of tumor heterogeneity. The patient had non-FDG-avid lung and bone metastases with PSMA uptake, whereas metastatic cervical and axillary lymph nodes showed vice versa, and skeletal muscle metastasis to vastus lateralis, which is an unusual region for metastasis, showed both PSMA and FDG positivity. In response assessment, mix response was detected. It seems that 68Ga-PSMA and 18F-FDG may have a complementary role in demonstration of metastasis accurately and assessment of treatment response in clear cell renal cell carcinoma.

Squamous Cell Carcinoma Mimicking Neck Paraganglioma on 68Ga-DOTATATE PET/CT.

ABSTRACT: Somatostatin receptor (SSTR) imaging with 68Ga-labeled somatostatin analogs has been used for many tumors with high SSTR expression. Increased uptake mostly depends on the SSTR status of tumors; however, false-positive uptake can be demonstrated in benign diseases or other malignancies because of the increased SSTR expression. We present a case of a 50-year-old man with increased SSTR activity on cervical lesion located in internal jugular chain in 68Ga-DOTATATE PET/CT, which was performed for suspicion of paraganglioma. Biopsy revealed lymph node metastasis of squamous cell carcinoma other than paraganglioma. 18F-FDG PET/CT showed primary malignancy on larynx and lymph node metastasis, which were correlated surgically.

177Lu-PSMA Therapy for Metastatic Testicular Mixed Germ Cell Tumor.

ABSTRACT: Prostate-specific membrane antigen (PSMA) overexpression in various tumors are demonstrated in both in vitro and in vivo studies. Prostate-specific membrane antigen-directed radionuclide therapies are generally used in prostate cancer and could be also useful in PSMA-avid other malignancies. Herein, we present a case of a 46-year-old male patient who had progressive metastatic testicular mixed germ cell tumor, despite repeated operations and treatments. 68Ga-PSMA PET/CT was performed to assess eligibility for 177Lu-PSMA therapy. Patient had intense PSMA uptake in metastatic lesions, and 177Lu-PSMA has been given to control of disease. However, α-fetoprotein level progressed, and mixed therapy response was detected in 68Ga-PSMA PET/CT.

Metastatic Poorly Differentiated Thyroid Cancer With Heterogeneous Distribution of 18F-FDG, 68Ga-DOTATATE, and 68Ga-PSMA on PET/CT.

ABSTRACT: We present a case of a 55-year-old man with a history of poorly differentiated metastatic thyroid cancer, which is rare and shows aggressive behavior. The patient had radioactive iodine-negative multiple metastasis on 18F-FDG PET/CT, therefore 68Ga-DOTATATE and 68Ga-PSMA PET/CT were performed whether an opportunity exist for DOTATATE or PSMA-directed radionuclide therapy. Different patterns of tumoral uptakes were detected on 18F-FDG, 68Ga-DOTATATE, and 68Ga-PSMA PET/CT, as a demonstration of tumor heterogeneity.

Does bone scintigraphy still have a role in the era of 68 Ga-PSMA PET/CT in prostate cancer?

OBJECTION: We aimed to evaluate the role of bone scintigraphy (BS) which has long been the imaging modality of choice in prostate cancer (PCa) and performed a head-to-head comparison between BS, BS + SPECT/CT and 68 Ga-PSMA-PET/CT, for the detection of bone metastasis of PCa. METHODS: We evaluated 138 PCa patients who underwent BS and 68 Ga-PSMA PET/CT and SPECT/CT of 102 of 138 patients. Images were interpreted retrospectively and areas of abnormally increased tracer uptake related to PCa were documented as benign, metastatic or equivocal. Equivocal uptakes were finally diagnosed based on a consensus review of correlative imaging. Patient- and lesion-based analysis was performed. Patients with superscan images were excluded from lesion-based analysis. RESULTS: At least one metastatic or equivocal uptake in skeleton was defined in 76 of 138 (55%) BS, in 33 of 102 (32.3%) SPECT/CT, and in 49 of 138 (35.5%) 68 Ga-PSMA PET/CT. 23 (16.7%) patients had also superscan findings on BS and 68 Ga-PSMA PET/CT. For patient-based analysis, sensitivity, specificity, accuracy, PPV, and NPV were calculated as 91.1%, 64.5%, 73.1%, 55.4% and 93.7% for BS; 95.5%, 82.7%, 86.9%, 72.8% and 96.2% for BS + SPECT/CT; 97.7%, 95.7%, 95.6%, 91.6% and 98.8% for 68 Ga-PSMA PET/CT. For lesion-based analysis, sensitivity, specificity, accuracy, PPV, and NPV were 53%, 63.9%, 60.1%, 42.8% and 71.8% for BS; 59.2%, 87.6%, 77.7%, 62.6% and 80% for BS + SPECT/CT; 96.4%, 98.1%, 97.5%, 96.4% and 98.1% for 68 Ga-PSMA PET/CT. CONCLUSION: This study has shown that 68 Ga-PSMA PET/CT overcomes the limitations of BS and proves superiority in detecting bone metastases, even in patients with SPECT/CT. Our findings present important implications that 68 Ga-PSMA PET/CT can replace BS in future practice.