Gallium-68 Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography in Active Surveillance for Prostate Cancer Trial (PASPoRT)

PSMA PET as a Tool for Active Surveillance of Prostate Cancer-Where Are We at?

Active surveillance remains the preferred treatment for men with low-risk prostate cancer and select men with favourable intermediate-risk prostate cancer. It involves the close observation of clinicopathological parameters to assess for disease progression, aiming to delay or avoid definitive treatment and related toxicities for as long as possible, without compromising oncological outcomes. A recent advancement in prostate cancer staging is the PSMA PET scan, which uses a tracer that strongly binds a highly expressed cellular biomarker for prostate cancer. Recent articles have also demonstrated that PSMA PET may be a useful tool for risk-stratifying prostate cancer, with the SUVMax of the scan correlated with higher-grade prostate cancer. This has ignited interest in the potential use of PSMA PET to identify men with higher-risk prostate cancer who may be unsuitable for active surveillance, particularly those who were incorrectly classified as lower risk upon initial diagnosis. This review article aims to assess the current state of the literature and clinical guidelines regarding the use of PSMA PET as a tool to risk-stratify prostate cancer, and whether it can be incorporated into active surveillance protocols to identify men who were incorrectly risk-stratified at time of initial diagnosis.

PSMA PET/CT in the diagnosis of prostate cancer: why and when?

Prostate-specific membrane antigen (PSMA) is expressed in most primitive and metastatic prostate cancer (PCa), and PSMA inhibitors conjugated with the radionuclides Gallium 68 (68Ga) and fluoride 18 (18F) have been evaluated to detect PCa; moreover, tumour uptake, which represents PSMA expression, is highly correlated with the aggressiveness of the primary prostatic tumour. PSMA positron emission tomography/computed tomography (PET/CT) demonstrated to be sensitive for the detection of primary prostatic lesions, regional lymphadenopathy and clinical metastases in case of biochemical recurrence. In this respect, PSMA PET/CT has been evaluated in men enrolled in clinical trials candidate to initial or repeat prostate biopsy especially in the presence of clinical high risk for PCa, Active Surveillance (AS) and/or in case of negative histology of Prostate Imaging Reporting and Data System (PI-RADS score) 4-5 targeted biopsy. Although many experimental studies reported a superimposable detection rate for PCa of PSMA PET/CT vs. mpMRI targeted biopsy, still today, the use of PSMA PET/CT is experimental and had some limitations: cost, availability, patient characteristics, local expertise and false negative rate. Although prospective and randomized studies are awaited, including a greater number of patients, PSMA PET/CT evaluation could be proposed in the presence of claustrophobia, cardiac pacemaker and severe obesity especially in men at high risk for PCa.

Early Results from the CONFIRM Trial: Utility of Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography in Active Surveillance for Prostate Cancer

BACKGROUND AND OBJECTIVE

There is growing evidence on the utility of prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) for detection of clinically significant prostate cancer (csPC), but there are limited data on its use in active surveillance (AS). The CONFIRM trial aims to determine the utility of PSMA PET/CT in detecting csPC before confirmatory biopsy during AS.

METHODS

This is an initial analysis of a prospective, nonrandomised, crossover clinical trial (ANZCTR ID ACTRN12621001648819) that included men on AS for newly diagnosed low-grade prostate cancer (PC) with "high-risk" features. High risk was defined as grade group (GG) 1 disease with elevated prostate-specific antigen (PSA; >10 ng/ml, or PSA density >0.15 ng/ml/ml), high-volume GG 1, GG 1 with Prostate Imaging-Reporting and Data System 4 or 5 lesion on magnetic resonance imaging (MRI), or low-volume GG 2 PC. Patients underwent multiparametric MRI and [18F]-labelled radioligand PSMA PET/CT 3-6 mo after diagnosis, and confirmatory biopsy 6-9 mo after diagnosis.

KEY FINDINGS AND LIMITATIONS

Between November 2021 and September 2023, 60 patients (median age 62.5 yr) were enrolled. PSMA-avid lesions were identified in 44 patients (73.3%), of whom 27 (61.4%) harboured csPC (GG ≥2). Of the PSMA-avid lesions, 20 (45.5%) were MRI-occult. At a subsequent multidisciplinary meeting, active treatment was recommended for 24 patients (40%), with PSMA PET/CT findings influencing 12 (20%) of the decisions. PSMA PET/CT provided reassurance regarding the decision to continue AS by excluding PSMA-avid lesions in 14 cases (38.9%) and multifocal disease in four (11.1%). Our findings are limited by the small sample size and short follow-up.

CONCLUSIONS AND CLINICAL IMPLICATIONS

PSMA PET/CT appears to hold promise for improving risk stratification during AS by identifying csPC and MRI-occult lesions.

Integrating Prostate Specific Membrane Antigen-PET into Clinical Practice for Prostate Cancer

Prostate surface membrane antigen (PSMA)-PET imaging has significantly shaped the clinical management of prostate cancer, from localized to metastatic disease. It outperforms conventional imaging in both primary staging and detecting recurrence. PSMA-PET incorporation into the clinical workflow can alter treatment decisions, though the impact of observed stage migration on patient outcomes has yet to be well-characterized. There is growing interest in using PSMA-PET to predict treatment response across all stages of prostate cancer, and to select patients for PSMA radioligand therapy. Use of PSMA-PET will continue to expand for clinical applications as its role becomes better defined through prospective studies.

MRI and active surveillance: thoughts from across the pond

In the United States (US), urological guidelines recommend active surveillance (AS) for patients with low-risk prostate cancer (PCa) and endorse it as an option for those with favorable intermediate-risk PCa with a > 10-year life expectancy. Multiparametric magnetic resonance imaging (mpMRI) is being increasingly used in the screening, monitoring, and staging of PCa and involves the combination of T2-weighted, diffusion-weighted, and dynamic contrast-enhanced T1-weighted imaging. The American Urological Association (AUA) guidelines provide recommendations about the use of mpMRI in the confirmatory setting for AS patients but do not discuss the timing of follow-up mpMRI in AS. The National Comprehensive Cancer Network (NCCN) discourages using it more frequently than every 12 months. Finally, guidelines state that mpMRI can be used to augment risk stratification but should not replace periodic surveillance biopsy. In this review, we discuss the current literature regarding the use of mpMRI for patients with AS, with a particular focus on the approach in the US. Although AS shows a benefit to the addition of mpMRI to diagnostic, confirmatory, and follow-up biopsy, there is no strong evidence to suggest that mpMRI can safely replace biopsy for most patients and thus it must be incorporated into a multimodal approach. CLINICAL RELEVANCE STATEMENT: According to the US guidelines, regular follow-ups are important for men with prostate cancer on active surveillance, and prostate MRI is a valuable tool that should be utilized, in combination with PSA kinetics and biopsies, for monitoring prostate cancer. KEY POINTS: According to the US guidelines, the addition of MRI improves the detection of clinically significant prostate cancer. Timing interval imaging of patients on active surveillance remains unclear and has not been specifically addressed. MRI should trigger further work-ups, but not replace periodic follow-up biopsies, in men on active surveillance.

Oncologic Outcomes of Incidental Versus Biopsy-diagnosed Grade Group 1 Prostate Cancer: A Multi-institutional Study

Background and objective

Patients diagnosed with grade group (GG) 1 prostate cancer (PCa) following treatment for benign disease ("incidental" PCa) are typically managed with active surveillance (AS). It is not known how their outcomes compare with those observed in patients diagnosed with GG1 on biopsy. We aimed at determining whether long-term oncologic outcomes of AS for patients with GG1 PCa differ according to the type of diagnosis: incidental versus biopsy detected.

Methods

A retrospective, multi-institutional analysis of PCa patients with GG1 on AS at eight institutions was conducted. Competing risk analyses estimated the incidence of metastases, PCa mortality, and conversion to treatment. As a secondary analysis, we estimated the risk of GG ≥2 on the first follow-up biopsy according to the type of initial diagnosis.

Key findings and limitations

A total of 213 versus 1900 patients with incidental versus biopsy-diagnosed GG1 were identified. Patients with incidental cancers were followed with repeated biopsies and multiparametric magnetic resonance imaging less frequently than those diagnosed on biopsy. The 10-yr incidence of treatment was 22% for incidental cancers versus 53% for biopsy (subdistribution hazard ratio [sHR] 0.34, 95% confidence interval [CI] 0.26-0.46, p < 0.001). Distant metastases developed in one patient with incidental cancer versus 17 diagnosed on biopsy and were diagnosed with molecular imaging in 13 (72%) patients. The 10-yr incidence of metastases was 0.8% for patients with incidental PCa and 2% for those diagnosed on biopsy (sHR 0.35, 95% CI 0.05-2.54, p = 0.3). The risk of GG ≥2 on the first follow-up biopsy was low if the initial diagnosis was incidental (7% vs 22%, p < 0.001).

Conclusions and clinical implications

Patients with GG1 incidental PCa should be evaluated further to exclude aggressive disease, preferably with a biopsy. If no cancer is found on biopsy, then they should receive the same follow-up of a patient with a negative biopsy. Further research should confirm whether imaging and biopsies can be avoided if postoperative prostate-specific antigen is low (<1-2 ng/ml).

Patient summary

We compared the outcomes of patients with low-grade prostate cancer on active surveillance according to the type of their initial diagnosis. Patients who have low-grade cancer diagnosed on a procedure to relieve urinary symptoms (incidental prostate cancer) are followed less intensively and undergo curative-intended treatment less frequently. We also found that patients with incidental prostate cancer are more likely to have no cancer on their first follow-up biopsy than patients who have low-grade cancer initially diagnosed on a biopsy. These patients have a more favorable prognosis than their biopsy-detected counterparts and should be managed the same way as patients with negative biopsies if they undergo a subsequent biopsy that shows no cancer.

The additional value of 68Ga-PSMA PET/CT SUVmax in predicting ISUP GG ≥ 2 and ISUP GG ≥ 3 prostate cancer in biopsy

BACKGROUND

Prebiopsy magnetic resonance imaging (MRI) increases the detection rate of clinically significant prostate cancer (csPCa). Prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA PET/CT) maximum standardized uptake value (SUVmax) of the prostate may offer additional value in predicting the likelihood of csPCa in biopsy.

METHODS

A single-center cohort study involving patients with biopsy-proven PCa who underwent both MRI and PSMA PET/CT between 2020 and 2021. Logistic regression models were developed for International Society of Urological Pathology (ISUP) Grade Group (GG) ≥ 2 and GG ≥ 3 using noninvasive prebiopsy parameters: age, (log-)prostate-specific antigen (PSA) density, PI-RADS 5 lesion presence, extraprostatic extension (EPE) on MRI, and SUVmax of the prostate. Models with and without SUVmax were compared using Likelihood ratio tests and area under the curve (AUC). DeLong's test was used to compare the AUCs.

RESULTS

The study included 386 patients, with 262 (68%) having ISUP GG ≥ 2 and 180 (47%) having ISUP GG ≥ 3. Including SUVmax significantly improved both models' goodness of fit (p < 0.001). The GG ≥ 2 model had a higher AUC with SUVmax 89.16% (95% confidence interval [CI]: 86.06%-92.26%) than without 87.34% (95% CI: 83.93%-90.76%) (p = 0.026). Similarly, the GG ≥ 3 model had a higher AUC with SUVmax 82.51% (95% CI: 78.41%-86.6%) than without 79.33% (95% CI: 74.84%-83.83%) (p = 0.003). The SUVmax inclusion improved the GG ≥ 3 model's calibration at higher probabilities.

CONCLUSION

SUVmax of the prostate on PSMA PET/CT potentially improves diagnostic accuracy in predicting the likelihood of csPCa in prostate biopsy.

Medium-term follow up of active surveillance for early prostate cancer at a non-academic institution

OBJECTIVES

To report oncological outcomes of active surveillance (AS) at a single non-academic institution adopting the standardised Prostate Cancer Research International Active Surveillance (PRIAS) protocol.

PATIENTS AND METHODS

Competing risk analyses estimated the incidence of overall mortality, metastases, conversion to treatment, and grade reclassification. The incidence of reclassification and adverse pathological findings at radical prostatectomy were compared between patients fulfilling all PRIAS inclusion criteria vs those not fulfilling at least one.

RESULTS

We analysed 341 men with Grade Group 1 prostate cancer (PCa) followed on AS between 2010 and 2022. There were no PCa deaths, two patients developed distant metastases and were alive at the end of the study period. The 10-year cumulative incidence of metastases was 1.9% (95% confidence interval [CI] 0.33-6.4%). A total of 111 men were reclassified, and 127 underwent definitive treatment. Men not fulfilling at least one PRIAS inclusion criteria (n = 43) had a higher incidence of reclassification (subdistribution hazards ratio 1.73, 95% CI 1.07-2.81; P = 0.03), but similar rates of adverse pathological findings at radical prostatectomy.

CONCLUSION

Metastases in men on AS at a non-academic institution are as rare as those reported in established international cohorts. Men followed without stringent inclusion criteria should be counselled about the higher incidence of reclassification and reassured they can expect rates of adverse pathological findings comparable to those fulfilling all criteria. Therefore, AS should be proposed to all men with low-grade PCa regardless of whether they are followed at academic institutions or smaller community hospitals.

The Current Landscape of Prostate-Specific Membrane Antigen (PSMA) Imaging Biomarkers for Aggressive Prostate Cancer

The review examines the vital role of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) in the diagnosis, staging, and treatment of prostate cancer (PCa). It focuses on the superior diagnostic abilities of PSMA PET/CT for identifying both nodal and distant PCa, and its potential as a prognostic indicator for biochemical recurrence and overall survival. Additionally, we focused on the variability of PSMA's expression and its impact on personalised treatment, particularly the use of [177Lu] Lu-PSMA-617 radioligand therapy. This review emphasises the essential role of PSMA PET/CT in enhancing treatment approaches, improving patient outcomes, and reducing unnecessary interventions, positioning it as a key element in personalised PCa management.

Active surveillance should not be routinely considered in ISUP grade group 2 prostate cancer

Active surveillance has been proposed as a therapeutic option in selected intermediate risk patients with biopsy grade group 2 prostate cancer. However, its oncologic safety in this setting is debated. Therefore, we conducted a non-systematic literature research of contemporary surveillance protocols including patients with grade group 2 disease to collect the most recent evidence in this setting. Although no randomized controlled trial compared curative-intent treatments, namely radical prostatectomy and radiotherapy vs. active surveillance in patients with grade group 2 disease, surgery is associated with a benefit in terms of disease control and survival when compared to expectant management in the intermediate risk setting. Patients with grade group 2 on active surveillance were at higher risk of disease progression and treatment compared to their grade group 1 counterparts. Up to 50% of those patients were eventually treated at 5 years, and the metastases-free survival rate was as low as 85% at 15-years. When considering low- and intermediate risk patients treated with radical prostatectomy, grade group 2 was one of the strongest predictors of grade upgrading and adverse features. Available data is insufficient to support the oncologic safety of active surveillance in all men with grade group 2 prostate cancer. Therefore, those patients should be counselled regarding the oncologic efficacy of upfront active treatment modalities and the lack of robust long-term data supporting the safety of active surveillance in this setting.