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OBJECTIVE: Recently, gallium-68-prostate-specific membrane antigen-11 (68Ga-PSMA-11) positron emission tomography/computed tomography (PET/CT) has become a key imaging method in prostate carcinoma staging and biochemical progression, with varying sensitivities in different studies (from 40% to 80%). After four years of experience with 68Ga-PSMA-11 PET/CT, we found that it is possible to detect lesions with increased PSMA expression in patients with undetectable prostate specific antigen (PSA) levels after radical prostatectomy. The key questions we wanted to answer were as follows: if those lesions were malignant and could the early detection of those malignant lesions have a role in patient management? We aimed to identify and follow up PSMA-positive findings for a period of 4 years in patients with prostate cancer after radical prostatectomy and undetectable PSA values at the time of the examination. We also explored false-positive lesions in detail. SUBJECTS AND METHODS: The study included all patients who underwent radical prostatectomy and had undetectable PSA values <0.05ng/mL and who underwent 68Ga-PSMA-11 PET/CT between July 2019 and December 2019. We performed 220 studies and found 40 patients with these characteristics; these patients were included in this study. All of them were followed up until July 2023. Any finding with increased radiopharmaceutical accumulation above the background activity in the respective area was considered a false positive. Prostate-specific membrane antigen accumulation in established lesions was assessed semi-quantitatively by the maximum standardized uptake value (SUVmax) and qualitatively by the four-point visual scale proposed in the E-PSMA recommendations. RESULTS: We found 15/40 (37.5%) patients with PSMA-positive findings. These were predominantly bone changes without a corresponding CT abnormality or discrete cystic or osteoblastic lesions with above-background increased PSMA expression. The mean SUVmax of these non-specific lesions was 3.02 (SD 2.86). After 3.5-4 years of follow-up, biochemical progression was found in only two of the patients.The great sensitivity of the method nowadays is a powerful engine for the development of new therapeutic options. On the other side, the lower specificity due to false positive findings, if misinterpreted, might lead to switching to a higher stage, with the planned radical treatment replaced by palliative treatment. CONCLUSION: The presence of 68Ga-PSMA-11 PET/CT-positive findings in patients after radical prostatectomy and an undetectable PSA had a low predictive value for future progression. The interpretation of 68Ga-PSMA-11 PET/CT should always include a complex assessment of the clinical setting-the risk group, PSA value and degree of PSMA accumulation in the lesions. In these situations, further clarification of PSMA-positive findings is appropriate before deciding to change treatment.

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BACKGROUND: Malignant melanoma stands out as a disease with highly aggressive behavior and frequent recurrences. It is crucial to find a non-invasive method for early recurrence detection which allows early and radical treatment. Our aim was to assess the diagnostic and clinical value of [18F]FDG PET/CT in the follow-up regimen of patients after radically treated first regional recurrence and for early detection of operable disease progression. MATERIAL AND METHODS: We performed [18F]FDG PET/CT in 96 consecutive patients who had a histologically proven regional recurrent disease that was radically treated. In 46 patients [18F]FDG PET/CT was used in the follow-up regimen and in the other 50 it was used for clarification of suspicious lesions seen in conventional studies. We explored the diagnostic performance of [18F]FDG PET/CT. We also compared the results with conventional studies and explored the clinical impact of [18F]FDG PET/CT by its ability to find localized disease progression in those groups. RESULTS: [18F]FDG PET/CT had better sensitivity, specificity, PPV and NPV, and accuracy in patients with symptoms. This good results in the second group had a high price for the patients, as there was a prevalence of distant metastatic disease in the second group - 64.0% vs. 28.3% in the surveillance group (p = 0.001). [18F]FDG PET/CT revealed more of the distant and in-transit lesions and assisted in lymph node detection by guiding the ultrasonography. Owing to the [18F]FDG PET/CT surveillance, 64.5% of all operable lesions were found in the surveillance group vs. only 35.5% in the second group, where the distant metastatic disease was prevalent. CONCLUSIONS: [18F]FDG PET/CT used as a follow-up tool in the surveillance regimen of patients after the first recurrence showed excellent performance in timely and accurate recognition of operable lesions. It had significantly better performance than conventional studies in the follow-up regimen of the patients in this high risk of progression group.

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BACKGROUND: Sarcomas comprise 1% of malignant tumors in adults but represent a significant diagnostic and therapeutic challenge. Molecular imaging with ¹8FDG PET/CT is a powerful modality in oncology. Its use for initial assessment, evaluation of response to therapy and recurrent disease in most tumors is essential for therapeutic decisions. Its indication in sarcomas is still controversial. One of the indications for PET/CT in sarcomas is detection of recurrences. Nowadays magnetic resonance tomography (MRT) has a crucial role in identification of local recurrences in soft tissue and bone sarcoma. ¹8FDG-PET/CT may serve as a complementary method. Dual time point imaging (DTPI) has been studied for most tumors as a method for differentiating benign from malignant lesions. There is limited data on DTPI in sarcomas. Therefore we studied prospectively patients with suspected local recurrences in the treated area and used DTPI as a method for differentiating benign from malignant tissue. THE AIM: of this study was to evaluate the ability of dual-time point PET/CT to enhance sensitivity, specificity, PPV, NPV and accuracy of ¹8FDG PET/CT in high grade and low grade sarcomas. MATERIAL AND METHODS: We conducted a dual-time PET/CT in 15 patients with suspected locally recurrent disease. The delayed scan was conducted on the 120th min in the suspected region. The interpretation of PET/CT was made both upon CT scan and metabolic scans. The percentage change over time per lesion was calculated (%DSUV). The increase in SUVmax with %DSUV > 10% in the late scanning was considered as indicative for malignancy. We assessed the sensitivity, specificity, accuracy, positive and negative predicting value of the interpretation of PET/CT at 60 min and 120 min. All of the patients were followed up for a period of 1-3 years after our examination, either with histologic results, or with an MRT scans. RESULTS: The received sensitivity, specificity and accuracy of ¹8FDG PET/CT interpretation at 120 min in high grade sarcomas were respectively 100%, 80% and 89%. By comparison, in low grade tumors at 120 min scan, these parameters were 50%, 75% and 66%. CONCLUSION: These preliminary data suggests that dual-time imaging in sarcomas improves sensitivity and accuracy in identification of local recurrent disease in high grade sarcomas and have limited role in low grade sarcomas. Further research is necessary to confirm these results.

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As fluorine-18-fluorodesoxyglucose positron emission tomography/computed tomography ( (18)F-FDG PET/CT) is gaining wider availability, more and more patients with malignancies undergo whole body PET/CT, mostly to assess tumor spread in the rest of the body, but not in the brain. Brain is a common site of metastatic spread in patients with solid extracranial tumors. Gold standard in the diagnosis of brain metastases remains magnetic resonance imaging (MRI). However MRI is not routinely indicated and is not available for all cancer patients. Fluorine-18-FDG PET is considered as having poor sensitivity in detecting brain metastases, but this may not be true for PET/CT. The aim of our study was to assess the value of (18)F-FDG PET/CT in the detection of brain metastases found by whole body scan including the brain, in patients with solid extracranial neoplasms. A total of 2502 patients with solid extracranial neoplasms were studied. All patients underwent a routine whole body (18)F-FDG PET/CT scan with the whole brain included in the scanned field. Patients with known or suspected brain metastases were preliminary excluded from the study. Hypermetabolic and ring-like brain lesions on the PET scan were considered as metastases. Lesions with CT characteristics of brain metastases were regarded as such irrespective of their metabolic pattern. Lesions in doubt were verified by MRI during first testing or on follow-up or by operation. Our results showed that brain lesions, indicative of and verified to be metastases were detected in 25 out of the 2502 patients (1%), with lung cancer being the most common primary. Twenty three out of these 25 patients had no neurological symptoms by the time of the scan. The detection rate of brain metastases was relatively low, but information was obtained with a minimum increase of radiation burden. In conclusion, whole body (18)F-FDG PET/CT detected brain metastases in 1% of the patients if brain was included in the scanned field. Brain scanning as a part of whole body scan cannot replace routine imaging techniques, but in case of positive findings provides early and crucial information for further patient management, especially in asymptomatic patients.

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