68 Ga-PSMA-11 PET/CT Imaging in Brain Gliomas and Its Correlation With Clinicopathological Prognostic Parameters.

BACKGROUND: Gliomas are the most common primary central nervous system tumors, of which the malignant gliomas account for 60%-75%. The primary and secondary brain malignancies are highly treatment resistant, and their marked angiogenesis attracts interest as a potential therapeutic target. The grade of gliomas, Ki-67 index, and IDH mutation status are among the major prognostic markers in gliomas. Prostate-specific membrane antigen (PSMA) is a zinc-dependent peptidase that is not only expressed in prostate cancer cells but also in the tumor neovasculature. The initial PSMA PET studies in central nervous system tumors using 68 Ga-HBED-CC-PSMA ( 68 Ga-PSMA-11) PET tracer confirmed selective target expression in gliomas of different grades, with higher expression in high-grade glioma compared with low-grade glioma. AIMS AND OBJECTIVES: The aim of the present study was to correlate and compare the 68 Ga-PSMA-11 and 18 F-FDG uptake in brain tumors with their clinicopathological prognostic parameters, so as to study their prognostic implications. In addition, the study also aimed to identify patients who are likely to benefit from potential PSMA-targeted therapies. PATIENTS AND METHODS: This ongoing prospective study was approved by the institutional scientific and medical ethics committee. The patients with primary or recurrent glioma lesions on MRI underwent regional brain PET/CT scanning with 68 Ga-PSMA-11 and 18 F-FDG. The final histopathology of the brain lesions (glioma grade), Ki-67 index, and IDH mutation status were compared with SUV max values of the 68 Ga-PSMA-11 and 18 F-FDG PET/CT. RESULTS: A total of 15 patients (13 males and 2 females; age range, 21-73 years; median age, 58 years) were included in this study analysis. Among the 15 patients, 10 were treatment naive and 2 were patients with recurrent glioma. Three patients turned out to be WHO grade I-II, 6 belonged to grade III, and 6 grade IV (glioblastoma multiforme) on final histopathology. The 68 Ga-PSMA-11 PET/CT showed tracer uptake in all high-grade gliomas with good tumor-to-background ratio. It was PSMA nonavid in 2/3 low-grade gliomas, and it showed low-grade uptake in 1/3 patients. PSMA expression (as evaluated by SUV max values) was significantly higher in higher-grade tumors, those with IDH mutation wildtype status, and higher Ki-67 indices. FDG PET SUV max also showed significant correlation with these prognostic parameters. CONCLUSIONS: In these preliminary results, PSMA PET appears to be an important tool in the evaluation and prognosis of gliomas. PSMA-directed theranostics can be explored as a personalized approach in gliomas with high PSMA uptake. However, with the limitation of small sample size, larger clinical trials are warranted to draw conclusive evidence regarding the same.

Comparison of Multiparametric Magnetic Resonance Imaging and Gallium-68 Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography for Detecting Carcinoma Prostate in Patients with Serum Prostate-Specific Antigen between 4 and 20 ng/ml.

INTRODUCTION: We carried out this study to compare the diagnostic accuracy of multiparametric magnetic resonance imaging (mpMRI) and gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography (Ga-68 PSMA PET/CT) to detect prostatic carcinoma in patients with serum prostate-specific antigen (PSA) between 4 and 20 ng/ml in prebiopsy setting. MATERIALS AND METHODS: This prospective study evaluated men with serum PSA values between 4 and 20 ng/ml. All patients underwent mpMRI and Ga-68 PSMA PET/CT, followed by 12-core transrectal ultrasonography (TRUS)-guided biopsy to detect prostatic carcinoma. The diagnostic accuracy of mpMRI and PSMA PET/CT scan was compared with histopathological findings. RESULTS: There were thirty patients included in the study with a median age of 73 years (age range: 69-79 years). The median total serum PSA was 8.0 ng/ml (5.0-19.9 ng/ml). Of these, 18 had an identifiable lesion on imaging and had histopathological findings suggestive of carcinoma prostate. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of mpMRI were 100%, 92.30%, 94.73%, and 100%, respectively, and that of PSMA PET scan were 94.44%, 100%, 100%, and 92.31%, respectively. The diagnostic accuracy of both was 96.67%. CONCLUSION: PSMA PET scan showed higher PPV and specificity while mpMRI showed higher sensitivity and NPV. The accuracy in predicting presence of carcinoma was the same for both. PSMA PET showed higher specificity and PPV and predicted the subsequent need of biopsy. In our study, the NPV of PET, though good, was lower than mpMRI. Prospective trials with larger sample size are needed. In combination, PET/MRI may achieve greater accuracy and may serve as investigation of choice.

Ga-68 DOTATATE Positron Emission Tomography/Computed Tomography in a Rare Case of Esthesioneuroblastoma.

We describe the Ga-68 DOTATATE positron emission tomography/computed tomography (PET/CT) findings of a 51-year-old man, operated for right esthesioneuroblastoma. Postoperative Ga-68 DOTATATE PET/CT revealed focal uptake anterior to sphenoid ostium on the right paramedian side, suspicious for residual disease. Magnetic resonance imaging showed an enhancing lesion in posterosuperior nasal cavity on the right side extending into the right sphenoid sinus. He underwent re-surgery and adjuvant chemoradiotherapy. The histopathology revealed residual olfactory neuroblastoma. The follow-up Ga-68 DOTATATE PET/CT was negative. This case emphasizes the role of Ga-68 DOTATATE PET/CT in the management, especially in residual or recurrent disease and potential radiotheranostics for these rare tumors.

A Comparative Study of Pituitary Volume Variations in MRI in Acute Onset of Psychiatric Conditions.

INTRODUCTION: The growing belief that endocrine abnormalities may underlie many mental conditions has led to increased use of imaging and hormonal assays in patients attending to psychiatric OPDs. People who are in an acute phase of a psychiatric disorder show Hypothalamic Pituitary Adrenal (HPA) axis hyperactivity, but the precise underlying central mechanisms are unclear. AIM: To assess the pituitary gland volume variations in patients presenting with new onset acute psychiatric illness in comparison with age and gender matched controls by using MRI. MATERIALS AND METHODS: The study included 50 patients, with symptoms of acute psychiatric illness presenting within one month of onset of illness and 50 age and gender matched healthy controls. Both patients and controls were made to undergo MRI of the Brain. A 0.9 mm slices of entire brain were obtained by 3 dimensional T1 weighted sequence. Pituitary gland was traced in all sagittal slices. Anterior pituitary and posterior pituitary bright spot were measured separately in each slice. Volume of the pituitary (in cubic centimetre- cm3) was calculated by summing areas. Significance of variations in pituitary gland volumes was compared between the cases and controls using Analysis of Covariance (ANOVA). RESULTS: There were significantly larger pituitary gland volumes in the cases than the controls, irrespective of psychiatric diagnosis (ANOVA, f=15.56; p=0.0002). Pituitary volumes in cases were 15.36% (0.73 cm3) higher than in controls. CONCLUSION: There is a strong likelihood of HPA axis overactivity during initial phase of all mental disorders along with increased pituitary gland volumes. Further studies including hormonal assays and correlation with imaging are likely to provide further insight into neuroanatomical and pathological basis of psychiatric disorders.