68 Ga-labeled Prostate-specific Membrane Antigen Positron Emission Tomography for Prostate Cancer Imaging: The New Kid on the Block—Early or Too Early to Draw Conclusions?

Semiquantitative Parameters in PSMA-Targeted PET Imaging with [18F]DCFPyL: Impact of Tumor Burden on Normal Organ Uptake

PURPOSE

In this study, we aimed to quantitatively investigate the biodistribution of [¹⁸F]DCFPyL in patients with prostate cancer (PCa) and to determine whether uptake in normal organs correlates with an increase in tumor burden.

PROCEDURES

Fifty patients who had been imaged with [¹⁸F]DCFPyL positron emission tomography/computed tomography (PET/CT) were retrospectively included in this study. Forty of 50 (80 %) demonstrated radiotracer uptake on [¹⁸F]DCFPyL PET/CT compatible with sites of PCa. Volumes of interests (VOIs) were set on normal organs (lacrimal glands, parotid glands, submandibular glands, liver, spleen, and kidneys) and on tumor lesions. Mean standardized uptake values corrected to lean body mass (SUL_mean) and mean standardized uptake values corrected to body weight (SUV_mean) for normal organs were assessed. For the entire tumor burden, SUL_mean/max, SUV_mean, tumor volume (TV), and the total activity in the VOI were obtained using tumor segmentation. A Spearman's rank correlation coefficient was used to investigate correlations between normal organ uptake and tumor burden.

RESULTS

There was no significant correlation between TV with the vast majority of the investigated organs (lacrimal glands, parotid glands, submandibular glands, spleen, and liver). Only the kidney showed significant correlation: With an isocontour threshold at 50 %, left kidney uptake parameters correlated significantly with TV (SUV_mean, ρ = - 0.214 and SUL_mean, ρ = - 0.176, p < 0.05, respectively).

CONCLUSIONS

Only a minimal sink effect with high tumor burden in patients imaged with [¹⁸F]DCFPyL was observed. Other factors, such as a high intra-patient variability of normal organ uptake, may be a much more important consideration for personalized dosimetry with PSMA-targeted therapeutic agents structurally related to [¹⁸F]DCFPyL than the tumor burden.

Molecular imaging of prostate cancer: Review of imaging agents, modalities, and current status

INTRODUCTION

The clinical course of Prostate cancer (PCa) are markedly diverse, ranging from indolent to highly aggressive disseminated disease. Molecular imaging techniques are playing an increasing role in early PCa detection, staging and disease recurrence. There are some molecular imaging modalities, radiotracers agents and its performance are important in current clinical practice PCa.

OBJECTIVE

This review summarizes the latest information regarding molecular imaging of PCa and is designed to assist urologists with ordering and interpreting these modalities and different radiotracers for different patients.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted up to September 2019. We selected the most recent and relevant original articles, metanalysis and reviews that have provided relevant information to guide molecular imaging modalities and radiotracers use.

EVIDENCE SYNTHESIS

In this review, we discuss 3 main molecular imaging modalities and 7 radiotracer technologies available.

CONCLUSIONS

The use molecular imaging modalities and radiotracers has a unique role in biochemical recurrence and diagnosis of ganglionar and bone progression of PCa. In the present time, no one of these molecular imaging modalities can be recommended over the classical work-up of abdominopelvic CT scan and bone scan, and large-scale and multi-institutional studies are required to validate the efficacy and cost utility of these new technologies.

Impact of 68Ga-PSMA PET/CT in the treatment of prostate cancer: Initial experience in Spain

Aim

To evaluate whether positron-emission tomography/computed tomography with ⁶⁸Ga-PSMA (⁶⁸Ga-PSMA PET/CT) influences the therapeutic management of patients with primary or recurrent prostate cancer (PCa).

Background

Although ⁶⁸Ga-PSMA PET/CT is one of the best options for staging or restaging patients with PCa, its availability is still very limited in Spain. The present study reports the results of the first group of patients in Spain who underwent ⁶⁸Ga-PSMA PET/CT imaging.

Materials and methods

All patients (n = 27) with a histological diagnosis of PCa who underwent ⁶⁸Ga-PSMA PET/CT prior to the definitive treatment decision at the only centre with this technology in Spain during 2017-2018 were included. Two nuclear medicine physicians and a radiologist reviewed the imaging studies. The clinical impact was assessed from a theoretical perspective, based on the treatment that would have been applied if no data from the ⁶⁸Ga-PSMA PET/CT were available.

Results

Most patients (n = 26; 96%) had persistent disease or biochemical recurrence after radical prostatectomy, radiotherapy, or combined treatment. One patient underwent ⁶⁸Ga-PSMA PET/CT imaging to stage high-risk PCa. Overall, ⁶⁸Ga-PSMA PET/CT was positive in 19 patients (70.4%). In 68.75% of these patients, none of the other imaging tests-MRI, CT, or bone scans-performed prior to the ⁶⁸Ga-PSMA PET/CT were able to detect the presence of cancerous lesions. Overall, the findings of the ⁶⁸Ga-PSMA PET/CT led to a modification of the therapeutic approach in 62.96% of the patients in the study.

Conclusions

⁶⁸Ga-PSMA PET/CT alters the therapeutic approach in a substantial proportion of patients with PCa.

The impact of very high initial PSA on oncological outcomes after radical prostatectomy for clinically localized prostate cancer

BACKGROUND

To analyze oncological outcomes of very high-risk patients with initial PSA 50-99.9 and ≥100 ng/ml who underwent radical prostatectomy (RP) for clinically localized prostate cancer.

METHODS

Overall, 2,811 RP patients (1992-2018) with negative preoperative CT-scan and bone scintigraphy were included. The impact of preoperative PSA level, categorized as 20-49.9 (n = 2,195) vs. 50-99.9 (n = 454) vs. ≥100 ng/ml (n = 162) on biochemical recurrence (BCR)-free survival, metastasis-free survival (MFS) and cancer-specific survival (CSS) was assessed using Kaplan-Meier and multivariable Cox regression models.

RESULTS

Median follow-up was 47.5 months. Ten-year BCR-free survival rates were 46.9 vs. 32.1 vs. 29.0% within PSA-categories 20-49.9 vs. 50-99.9 vs. ≥100 ng/ml, respectively (P < 0.001). Ten-year MFS rates were 78.4 vs. 67.2 vs. 37.3% within PSA-categories 20-49.9 vs. 50-99.9 vs. ≥100 ng/ml (P < 0.001). 10-year CSS rates were 93.7 vs. 85.5 vs. 66.7% within PSA-categories 20-49.9 vs. 50-99.9 vs. ≥100 ng/ml (P < 0.001). In multivariable analyses, PSA-categories 50-99.9 ng/ml and ≥100 ng/ml were independently predicting higher risk of BCR (hazard ratio [HR]: 1.3 and 1.4), metastatic progression (HR: 1.4 and 2.3), and cancer-specific mortality (CSM, HR: 1.9 and 3.4) compared with PSA-category 20-49.9 ng/ml.

CONCLUSION

Initial PSA levels ≥50 ng/ml are associated with higher risk of BCR, metastatic progression, and CSM compared with high-risk patients with PSA of 20-49.9 ng/ml. In consequence, these patients may be counseled about a potentially increased risk of undetected metastases prior to RP possibly necessitating intensified multimodal treatments in the future.

MRI-Guided Ultrafocal HDR Brachytherapy for Localized Prostate Cancer: Median 4-Year Results of a feasibility study

PURPOSE

For the treatment of localized prostate cancer, focal therapy has the potential to cure with fewer side effects than traditional whole-gland treatments. We report an update on toxicity, quality of life (QoL), and tumor control in our magnetic resonance imaging (MRI)-guided ultrafocal high-dose-rate brachytherapy cohort.

METHODS AND MATERIALS

Disease status was evaluated by systematic biopsies and 3T multiparametric MRI. The brachytherapy implant procedure under fused transrectal ultrasound/MRI guidance was followed by a 1.5 T MRI for contour adjustments and catheter position verification. A single dose of 19 Gy was delivered to the tumor with a margin of 5 mm. Genitourinary (GU) toxicity, gastrointestinal (GI) toxicity, and erectile dysfunction (ED) were graded with the Common Terminology Criteria for Adverse Events version 4.0. QoL was measured with RAND-36, European Organisation for Research and Treatment of Cancer QLQ-C30 and PR25. International Prostate Symptom Scores and International Index of Erectile Function scores were obtained. Prostate-specific antigen level was monitored, with biochemical recurrence defined as nadir + 2 ng/mL (Phoenix).

RESULTS

Thirty patients with National Comprehensive Cancer Network low- (13%) to intermediate-risk (87%) prostate cancer were treated between May 2013 and April 2016. Median follow-up was 4 years. Median age was 71 years (interquartile range, 68-73) and median initial prostate-specific antigen level was 7.3 ng/mL (5.2-8.1). Maximum Gleason score was 4 + 3 = 7 (in 2 patients). All tumors were radiologic (MRI) stage T2. No grade >2 GU or >1 GI toxicity occurred. International Prostate Symptom Scores only deteriorated temporarily. Mild pretreatment ED deteriorated to moderate/severe ED in 50% of patients. Long-term clinically relevant QoL deterioration was seen in sexual activity and tiredness, whereas emotional and cognitive functioning improved. At 4 years, biochemical disease-free survival was 70% (95% confidence interval, 52%-93%), metastases-free survival was 93% (85%-100%), and overall survival was 100%. Of intraprostatic recurrences, 7 of 9 were out of field.

CONCLUSIONS

Ultrafocal high-dose-rate brachytherapy conveys minimal GU or GI toxicity and has a marginal effect on QoL. An early decline in erectile function was seen. Tumor control outcomes are poor (biochemical disease-free survival of 70% [52%-93%] at 4 years), most likely as a result of poor patient selection.

PSMA-PET/CT-Positive Paget Disease in a Patient with Newly Diagnosed Prostate Cancer: Imaging and Bone Biopsy Findings

A 67-year-old man diagnosed with Gleason score 4 + 5 = 9 clinically localized prostate cancer with ⁶⁸Ga-labeled prostate-specific membrane antigen-targeted ligand positron emission tomography/computed tomography (PSMA-PET/CT) positive Paget bone disease is described. Immunohistochemical staining revealed weak PSMA positivity of the bone lesion supporting the hypothesis that neovasculature might explain positive PSMA-PET/CT findings in Paget disease.