M. R. A. Pillai

(68)Ga-PSMA PET/CT imaging in primary hepatocellular carcinoma.

Ga-labelled prostate-specific membrane antigen (PSMA) is emerging as the tool with the most potential for imaging recurrent prostate cancer [1]. There have been a few reports of significant accumulation of the tracer in metastatic clear cell renal carcinoma [2] and metastatic breast cancer [3]. The expression of PSMA in tumour-associated vasculature of breast cancer and primary gliomas has been reported [4]. Similar to prostate cancer, F-FDG PET/CT is also not the best imaging option in primary hepatocellular carcinoma (HCC). The potential of Ga-PSMA for imaging primary HCC is not yet documented. We report the case of a 78-year-old man who presented with anorexia, significant weight loss, hepatomegaly and obstructive urinary symptoms. CT imaging of the abdomen revealed a large space-occupying lesion in liver with lytic bone lesions, miliary lung lesions and an enlarged prostate gland. The PSA level of the patient was elevated (17 ng/ml) and hence a Ga-PSMA PET/ CT scan was done, which revealed intense tracer accumulation in the liver lesion (c) with mild tracer uptake in the bone lesions (d) and lung lesions (e), with no abnormal tracer uptake in the prostate gland (b). He underwent a biopsy of the liver lesion which revealed primary HCC. A literature search revealed that 95 % of HCC stain positive for PSMA in the tumour vasculature [5]. The patient was started on sorafenib for metastatic HCC. Our experience shows that Ga-PSMA might be useful for imaging HCC, and it also opens the possibility of PSMA-based theranostics in HCC.

68Ga-PSMA PET/CT False-Positive Tracer Uptake in Paget Disease.

65-year-old man with left-sided pelvic pain on evaluation was found to have features suggestive of either Paget disease or prostatic bone metastasis of the left hemipelvis based on Tc-MDP bone scan and MRI. Ga-PSMA PET/CT to assess the possibility of primary prostate cancer and if present to stage it helped to rule out prostate cancer because of absence of focal abnormal increased tracer uptake in the prostate gland. However, false-positive tracer uptake was noted in the left hemipelvis, which was subject to biopsy and histopathologically proven to be Paget disease involvement.

Diagnostic Value of 68Ga PSMA-11 PET/CT Imaging of Brain Tumors-Preliminary Analysis.

Objective To evaluate the feasibility of using 68Ga PSMA-11 PET/CT for imaging brain lesions and its comparison with 18F-FDG. Methods Ten patients with brain lesions were included in the study. Five patients were treated cases of glioblastoma with suspected recurrence. 18F-FDG and 68Ga PSMA-11 brain scans were done for these patients. Five patients were sent for assessing the nature (primary lesion/metastasis) of space occupying lesion in brain. They underwent whole body 18F-FDG PET/CT scan and a primary site elsewhere in the body was ruled out. Subsequently they underwent 68Ga PSMA-11 brain PET/CT imaging. Target to background ratios (TBR) for the brain lesions were calculated using contralateral cerebellar uptake as background. Results In five treated cases of glioblastoma with suspected recurrence the findings of 68Ga PSMA-11 PET/CT showed good correlation with that of 18F-FDG PET/CT scan. Compared to the 18F-FDG, 68Ga PSMA-11 PET/CT showed better visualization of the recurrent lesion (presence/absence) owing to its significantly high TBR. Among the five cases evaluated for lesion characterization glioma and atypical meningioma patients showed higher SUVmax in the lesion with 68Ga PSMA-11 than with 18F-FDG and converse in cases of lymphoma. TBR was better with 68Ga PSMA PET/CT in all cases. Conclusion 68Ga PSMA-11 PET/CT brain imaging is a potentially useful imaging tool in the evaluation of brain lesions. Absence of physiological uptake of 68Ga PSMA-11 in the normal brain parenchyma results in high TBR values and consequently better visualization of metabolically active disease in brain.

Preparation of [68Ga]PSMA-11 for PET–CT imaging using a manual synthesis module and organic matrix based 68Ge/68Ga generator

INTRODUCTION [(68)Ga]PSMA-11 is a relatively recently introduced radiopharmaceutical for PET-CT imaging of prostate cancer patients. The availability of (68)Ge/(68)Ga generator and PSMA-11 ligand from commercial sources is facilitating the production of the radiopharmaceutical in-house. This paper describes our experience on the preparation of ~200 batches of [(68)Ga]PSMA-11 for conducting PET-CT imaging in patients suspected/suffering from prostate cancer. METHODS The radiosynthesis of [(68)Ga]PSMA-11 was done in a hospital based nuclear medicine department using (68)Ge/(68)Ga generator and a manual synthesis module, both supplied by Isotope Technologies Garching (ITG), Germany. The production involved the reaction of 5μg (5.3nmol) of PSMA-11 ligand in 1 ml of 0.25M sodium acetate buffer with 4ml of (68)GaCl3 in 0.05M HCl for 5min at 105°C; followed by purification in a C18 cartridge and collection through a 0.22μm pore size filter. RESULTS The radiochemical yields obtained were consistently high, 93.19%±3.76%, and there was hardly any batch failure. The radiochemical purity of the product was >99% and the product was stable for over 2h; however it was used in patients immediately after preparation. About 200 batches of [(68)Ga]PSMA-11 were prepared during the period and more than 300 patients received the tracer during the 14months of study. No adverse reaction was observed in any of the patients and the image qualities were consistent with literature reports. CONCLUSION [(68)Ga]PSMA-11 with high radiochemical and radionuclidic purity is conveniently prepared by using a (68)Ge/(68)Ga generator and manual synthesis module. The radiochemical yields are very high; and activity sufficient for 3-4 patients can be prepared in a single batch; multiple batches can be done on the same day and when needed after a gap of 1.5-2h.

68Ga-PSMA PET/CT Imaging in Multiple Myeloma.

The potential applications of Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT in the imaging of prostate cancer are now well established. A few case reports regarding the potential use of Ga-PSMA PET/CT in nonprostate cancer malignancies are also published. Apparently, the tumor neoangiogenesis is the mechanism attributed to increased Ga-PSMA uptake in the tumor sites in nonprostatic malignancies. We describe the use of Ga-PSMA PET/CT in imaging multiple myeloma. The intense Ga-PSMA avidity of the lesions also opens up the possibility of theranostics with Lu-PSMA.

Erratum to: A rare case of rectal carcinoma and prostate carcinoma with coexistent Paget’s disease mimicking bone metastases in both 18F-FDG and 68Ga PSMA PET/CT

F-FDG PET/CT for initial staging in a 68-year-old man with moderately differentiated adenocarcinoma of the rectum showed intense FDG uptake in the primary site in the rectum (Fig. 1B,C yellow arrow) and mild to moderate heterogeneous FDG uptake in diffuse sclerotic lesions involving the left hemipelvis, proximal aspects of left femur, and L5 vertebra (Fig. 1A, red arrow, Fig. 1D,E). Incidentally, per rectal examination revealed a hard nodule in the right half of the prostate and his serum prostatespecific antigen (sPSA) level was elevated (11 ng/mL). Subsequent biopsy revealed adenocarcinoma of the prostate (Gleason score – 7), and a Ga PSMA PET/CT for initial staging showed intense tracer uptake in the primary site in the prostate (Fig. 1F,J green arrow) and mild to moderate heterogeneous tracer uptake in the bone lesions (Fig. 1G-I, red arrow) similar to that seen in F-FDG PET/ CT. As the pattern was not definitive for bone metastases from either the rectum or prostate, a bone biopsy from the left iliac crest was done, which revealed Paget’s disease. The role of F-FDG PET/CT in colorectal cancer [1] and Ga PSMA PET/CT in prostate cancer is well established [2]. False positive uptake in Paget’s disease in F-FDG PET/CT [3] and Ga PSMA PET/CT is published [4]. This case reinforces the fact that atypical findings on PET/CT warrant careful interpretation and often histopathological correlation.

68Ga-PSMA PET/CT Imaging and 153Sm-EDTMP Bone Pain Palliation Therapy.

Ga-labeled prostate-specific membrane antigen (PSMA) is a potential tool in the imaging of recurrent prostate cancer. Ga-PSMA imaging is also useful for radiotherapy planning and in targeted therapy with Lu-PSMA. A few case reports regarding the use of Ga-PSMA in nonprostate cancer malignancies are also reported. We describe the use of Ga-PSMA imaging before Sm-EDTMP bone pain palliation therapy in a 58-year-old hormone refractory prostate cancer patient with extensive bone metastases.

68Ga-PSMA Uptake in an Incidentally Detected Gastrointestinal Stromal Tumor in a Case of Suspected Carcinoma Prostate

A 74-year-old man with suspected prostate cancer and a previously negative transrectal ultrasound-guided prostate biopsy underwent Ga-PSMA PET/CT. Scan showed no abnormal tracer concentration in enlarged prostate gland to suggest prostate cancer. Note was made of an incidentally detected well defined soft tissue lesion in the greater curvature of the stomach with moderate tracer concentration in its intraluminal portion. Biopsy of the lesion revealed gastrointestinal stromal tumor.

False Positive Uptake in Bilateral Gynecomastia on 68Ga-PSMA PET/CT Scan

A 66-year-old man on hormonal therapy with prostate cancer was referred for Ga-PSMA PET/CT scan for biochemical recurrence. Ga-PSMA PET/CT scan detected moderate heterogeneous tracer concentration in bilateral breast parenchyma, in addition to the abnormal tracer concentration in enlarged prostate gland, right external iliac lymph node, and sclerotic lesion in L4 vertebra. On clinical examination, he was found to have bilateral gynecomastia. Abnormal concentration of Ga-PSMA in breast cancer is now well known, and in this context, it is important to know that tracer localization can occur in gynecomastia as well, as evidenced in this case.

68Ga-DOTA Ubiquicidin PET/CT in an Infected Implant.

We describe the case of a 55-year-old man who presented with history of fever for 3 months that began 2 months after he had undergone open reduction and internal fixation of left humerus fracture. Implant infection was suspected, but conventional imaging remained unyielding. Ga-DOTA ubiquicidin PET/CT showed increased tracer uptake along the entire length of the implant in the left humerus. Implant removal and temporary external fixation were done. In 24 hours, the patient became afebrile, and blood culture on the fourth day was sterile.