Bone metastases in prostate cancer - Gallium-68-labeled prostate-specific membrane antigen or Fluorine 18 sodium fluoride PET/computed tomography - the better tracer?

OBJECTIVE: The objective was to assess the roles of 68Ga-PSMA PET/CT and 18F-NaF PET/CT in evaluation of skeletal metastatic lesions in prostate cancer. METHODS: Two hundred consecutive prostate cancer patients who had undergone 68Ga-PSMA PET/CT and 18F-NaF PET/CT at baseline evaluation (n = 80) and following suspected recurrence or disease progression (restaging) (n = 120) were analyzed retrospectively. RESULTS: PSMA and NAF scans were positive for skeletal metastatic lesions in 67% (134 patients) and negative in 33% (66 patients). The scans were concordant in 80% (160 patients: 66 negative and 94 positive) and discordant in 20% (40 patients). Among 40 discordant results, 14 were baseline and 26 were restaging studies. PSMA detected more number of lesions in 11 (nine baseline and two restaging). These were true positive marrow or lytic metastatic lesions. NaF revealed more number of lesions in 29 (5 initial and 24 restaging). These were false positive on follow-up imaging. No statistical difference (P value = 0.7 by McNemar test) between the two scans for identifying absence or presence of at least one skeletal lesion was noted at baseline staging. CONCLUSION: Though, both 18F-NaF and 68Ga-PSMA are excellent tracers for evaluation of skeletal metastases in prostate cancer, there is a distinct advantage of 68Ga-PSMA PET/CT due to detection of additional skeletal lesions and absence of false positive lesions. In addition, absence of PSMA avidity in healed metastases in the restaging setting opens up new avenue for assessment of response of skeletal metastases.

Vigorous achalasia: Zebra amongst horses.

Vigorous achalasia is an oesophageal disorder with clinical and radiological characteristics of classic achalasia and diffuse oesophageal spasm. It is a rarely reported variant. A 60-year-old gentleman presented with complaints of difficulty in swallowing, regurgitation and chest pain for the past 10 years. His symptoms persisted despite the use of proton pump inhibitors. On endoscopy and barium swallow, the diagnosis of vigorous achalasia was confirmed. It is a rare variant of classic achalasia usually misdiagnosed as diffuse oesophageal spasm.

Pilot study comparing dominant intraprostatic lesion volume using Ga-68 prostate-specific membrane antigen PET-computed tomography and multiparametric MRI.

PURPOSE: The standard imaging used for delineation of dominant intraprostatic lesion (DIL) is multiparametric MRI (mpMRI). The use of biologic imaging such as Ga-68 prostate-specific membrane antigen (PSMA) PET-computed tomography (PET-CT) for this purpose is being explored in view of increased sensitivity of this modality and the associated ease of delineation. MATERIALS AND METHODS: The primary objective of the study was to compare the autogenerated volumes of the DIL in Ga-68 PSMA PET-CT with the standard volume delineated in mpMRI. Twenty patients with biopsy-proven untreated prostatic adenocarcinoma were included. Multiple percentages of the maximum standardized uptake value (%SUVmax) were used to autogenerate DIL volumes in Ga-68 PSMA PET-CT and these volumes were numerically matched with the consensus DIL volume in mpMRI. PSMA tumor volume (PSMA-TV) and total lesion PSMA (TL-PSMA) were also calculated for each lesion. RESULTS: Median volume of DIL in mpMRI was 4 cm (interquartile range, IQR = 2.5-7.6 cm). The IQR for interobserver variability was 0.5-2.5 cm. Median SUVmax of the DIL was 14.1 (IQR = 10.2-22.3). Median %SUVmax corresponding to mpMRI volume was 41% of SUVmax (IQR = 34-55%). There was a strong negative correlation between MRI volume and %SUVmax (r = -0.829, P < 0.001). There was a significant correlation between TL-PSMA and prostate-specific antigen (r = 0.609, P = 0.004). CONCLUSIONS: The median DIL volume was 4 cm and median %SUVmax corresponding to MR volume of DIL was 41%. A strong inverse relationship is found between mpMRI-defined DIL volume and the %SUVmax which generates similar volume in Ga-68 PSMA PET-CT. TL-PSMA could be a quantitative biomarker for tumor load and prognosis.

Initial experience of Ga-68 prostate-specific membrane antigen positron emission tomography/computed tomography imaging in evaluation of biochemical recurrence in prostate cancer patients.

Gallium-68 labeled prostate-specific membrane antigen (Ga-68 PSMA) ligand (HBED-CC) is a novel tracer used for prostate cancer imaging. The aim of the study was to investigate the performance of Ga-68 PSMA positron emission tomography/computed tomography (PET/CT) in patients with biochemical recurrence (BCR) after definitive treatment. Scans of 96 consecutive patients were analyzed. Sixty-two patients received external beam radiotherapy, 34 underwent radical prostatectomy (RP), and 20 patients were on androgen deprivation therapy. Patients with prostate-specific antigen (PSA) level ≥>0.2 ng/mL following RP and PSA rise by 2 ng/mL or more above the nadir PSA following RT (Phoenix criteria) was considered as BCR, respectively. All patients underwent contrast-enhanced PET/CT after injection of 67-111 MBq Ga-68 PSMA ligand. Detection rates were correlated with serum PSA level. Detection rate for nodal metastases was compared with CT. Results of the scan were validated by using either biopsy or follow-up imaging or clinical follow-up. Seventy-four (77%) patients showed abnormal finding in Ga-68 PSMA PET/CT. The median serum PSA level of the population was 5.5 ng/ml (range 0.2-123 ng/ml). The median PSA of the positive scans was higher than that of the negative scans (6 vs. 1.7 ng/ml) and was statistically significant (P = 0.001 by Mann-Whitney U-test). In post-RP group, the detection rates were 23%, 50%, and 82% for PSA <1, 1-2, and >2 ng/ml, respectively. For post-RT, the detection was 86%, 85%, and 95% for PSA 2-5, 5.1-10, and >10 ng/ml, respectively. PSMA PET/CT revealed nodal metastases in 52 (54%) patients while CT showed pathological nodes only in 27 (28%) patients. Overall PSMA PET/CT revealed more number of nodes than CT (111 vs. 48 nodal station). PSMA PET/CT showed relapse in prostate/prostatic bed in 26 (27%) patients, nodal metastases in 50 (52%), skeletal metastases in 20 (21%), and other sites in 4 (4%) patients. Ga-68 PSMA PET/CT has high detection rate for localizing the site of recurrence in patients with biochemical failure and is superior to CT scan in the detection of nodal disease.

Role of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Various Orbital Malignancies.

Orbital swelling comprises wide spectrum of pseudotumors, benign and malignant tumor. Malignant tumor may be primary or secondary tumor, and they constitute about 36% of orbital tumors in adult. Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scan is extensively used in hematological malignancies and in solid tumors for staging, treatment response, and restaging. Recently, the use of FDG-PET/CT in orbital malignancies has gained importance. The aim of this pictorial essay is to illustrate few important orbital malignancies detected in F-18 FDG-PET/CT and discuss its role in assessing the primary lesion and associated systemic finding.

An Infrequent Case of Adult Alveolar Rhabdomyosarcoma with Pancreatic Metastases Detected in F-18 FDG PET/CT.

Rhabdomyosarcoma (RMS) is a rare cancer in adults, comprising about 1% of all forms of adult cancer. Common sites of metastases are lungs, skeletal system, lymph nodes, and brain. Metastases of RMS to pancreas are infrequent. We report a case of adult orbital alveolar RMS with pancreatic metastases detected in F-18-fluorodeoxyglucose-positron emission tomography/computed tomography.

Rare case of thoracic kidney detected by renal scintigraphy.

Intrathoracic kidney is a rare congenital abnormality with lowest frequency among all renal ectopias. Patients with thoracic kidneys are usually asymptomatic, and the condition is usually discovered incidentally during radiological evaluation for other conditions or during thoracic surgery. We report a case of a 62-year-old male who was referred to our department for renal scintigraphy for a nonvisualized left kidney on ultrasonography report. Both Tc-99m dimercaptosuccinic acid and diethylenetriaminepentaacetic acid scans revealed a left thoracic kidney which was confirmed by CT scan of the thorax and abdomen.