Preoperative 68Ga-PSMA PET/CT defines a subgroup of high-risk prostate cancer patients with favorable outcomes after radical prostatectomy and lymph node dissection

Development and validation of [18 F]-PSMA-1007 PET-based radiomics model to predict biochemical recurrence-free survival following radical prostatectomy

PURPOSE

Biochemical recurrence (BCR) following radical prostatectomy (RP) is a significant concern for patients with prostate cancer. Reliable prediction models are needed to identify patients at risk for BCR and facilitate appropriate management. This study aimed to develop and validate a clinical-radiomics model based on preoperative [18 F]PSMA-1007 PET for predicting BCR-free survival (BRFS) in patients who underwent RP for prostate cancer.

MATERIALS AND METHODS

A total of 236 patients with histologically confirmed prostate cancer who underwent RP were retrospectively analyzed. All patients had a preoperative [18 F]PSMA-1007 PET/CT scan. Radiomics features were extracted from the primary tumor region on PET images. A radiomics signature was developed using the least absolute shrinkage and selection operator (LASSO) Cox regression model. The performance of the radiomics signature in predicting BRFS was assessed using Harrell's concordance index (C-index). The clinical-radiomics nomogram was constructed using the radiomics signature and clinical features. The model was externally validated in an independent cohort of 98 patients.

RESULTS

The radiomics signature comprised three features and demonstrated a C-index of 0.76 (95% CI: 0.60-0.91) in the training cohort and 0.71 (95% CI: 0.63-0.79) in the validation cohort. The radiomics signature remained an independent predictor of BRFS in multivariable analysis (HR: 2.48, 95% CI: 1.47-4.17, p < 0.001). The clinical-radiomics nomogram significantly improved the prediction performance (C-index: 0.81, 95% CI: 0.66-0.95, p = 0.007) in the training cohort and (C-index: 0.78 95% CI: 0.63-0.89, p < 0.001) in the validation cohort.

CONCLUSION

We developed and validated a novel [18 F]PSMA-1007 PET-based clinical-radiomics model that can predict BRFS following RP in prostate cancer patients. This model may be useful in identifying patients with a higher risk of BCR, thus enabling personalized risk stratification and tailored management strategies.

A systematic review and meta-analysis to evaluate the diagnostic accuracy of PSMA PET/CT in the initial staging of prostate cancer

BACKGROUND

Positron Emission Tomography-Computed Tomography using Prostate-Specific Membrane Antigen (PSMA PET/CT) is notable for its superior sensitivity and specificity in detecting recurrent PCa and is under investigation for its potential in pre-treatment staging. Despite its established efficacy in nodal and metastasis staging in trial setting, its role in primary staging awaits fuller validation due to limited evidence on oncologic outcomes. This systematic review and meta-analysis aims to appraise the diagnostic accuracy of PSMA PET/CT compared to CI for comprehensive PCa staging.

METHODS

Medline, Scopus and Web of science databases were searched till March 2023. Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines were followed to identify eligible studies. Primary outcomes were specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV) of PSMA PET/CT for local, nodal and metastatic staging in PCa patients. Due to the unavailability of data, a meta-analysis was feasible only for detection of seminal vesicles invasion (SVI) and LNI.

RESULTS

A total of 49 studies, comprising 3876 patients, were included. Of these, 6 investigated accuracy of PSMA PET/CT in detection of SVI. Pooled sensitivity, specificity, PPV and NPV were 42.29% (95%CI: 29.85-55.78%), 87.59% (95%CI: 77.10%-93.67%), 93.39% (95%CI: 74.95%-98.52%) and 86.60% (95%CI: 58.83%-96.69%), respectively. Heterogeneity analysis revealed significant variability for PPV and NPV. 18 studies investigated PSMA PET/CT accuracy in detection of LNI. Aggregate sensitivity, specificity, PPV and NPV were 43.63% (95%CI: 34.19-53.56%), 85.55% (95%CI: 75.95%-91.74%), 67.47% (95%CI: 52.42%-79.6%) and 83.61% (95%CI: 79.19%-87.24%). No significant heterogeneity was found between studies.

CONCLUSIONS

The present systematic review and meta-analysis highlights PSMA PET-CT effectiveness in detecting SVI and its good accuracy in LNI compared to CI. Nonetheless, it also reveals a lack of high-quality research on its performance in clinical T staging, extraprostatic extension and distant metastasis evaluation, emphasizing the need for further rigorous studies.

Impact of Circulating Tumor Cell-Expressed Prostate-Specific Membrane Antigen and Prostate-Specific Antigen Transcripts in Different Stages of Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA)-based images, which visually quantify PSMA expression, are used to determine prostate cancer micrometastases. This study evaluated whether a circulating tumor cell (CTC)-based transcript platform, including PSMA mRNA, could help identify potential prognostic markers in prostate cancer.

EXPERIMENTAL DESIGN

We prospectively enrolled 21 healthy individuals and 247 patients with prostate cancer [localized prostate cancer (LPCa), n = 94; metastatic hormone-sensitive prostate cancer (mHSPC), n = 44; and metastatic castration-resistant prostate cancer (mCRPC), n = 109]. The mRNA expression of six transcripts [PSMA, prostate-specific antigen (PSA), AR, AR-V7, EpCAM, and KRT 19] from CTCs was measured, and their relationship with biochemical recurrence (BCR) in LPCa and mCRPC progression-free survival (PFS) rate in mHSPC was assessed. PSA-PFS and radiological-PFS were also calculated to identify potential biomarkers for predicting androgen receptor signaling inhibitor (ARSI) and taxane-based chemotherapy resistance in mCRPC.

RESULTS

CTC detection rates were 75.5%, 95.3%, and 98.0% for LPCa, mHSPC, and mCRPC, respectively. In LPCa, PSMA [hazard ratio (HR), 3.35; P = 0.028) and PSA mRNA (HR, 1.42; P = 0.047] expressions were associated with BCR. Patients with mHSPC with high PSMA (HR, 4.26; P = 0.020) and PSA mRNA (HR, 3.52; P = 0.042) expressions showed significantly worse mCRPC-PFS rates than those with low expression. Increased PSA and PSMA mRNA expressions were significantly associated with shorter PSA-PFS and radiological PFS in mCPRC, indicating an association with drug resistance.

CONCLUSIONS

PSMA and PSA mRNA expressions are associated with BCR in LPCa. In advanced prostate cancer, PSMA and PSA mRNA can also predict rapid progression from mHSPC to mCRPC and ARSI or taxane-based chemotherapy resistance.

Correlation between pre-radical prostatectomy standardized SUVmax ratios detected on 68Ga-PSMA-I&T PET/CT and final histopathology outcomes: an in-depth analysis

OBJECTIVE

To evaluate the predictive potential of the maximum standardized uptake value(SUVmax) value of intraprostatic tumors derived from preoperative 68Ga-PSMA-I&T PET/CT (SUVT), and its ratios to SUVmax in the liver (SUVTLR) and parotid gland (SUVTPR) with respect to histopathological findings.

MATERIALS AND METHODS

Data from patients who underwent radical prostatectomy (RP) for prostate cancer (PC) at our clinic between 2017 and 2020 were assessed. Patients with a secondary malignancy, a history of transurethral prostate resection, prior treatment for PC, or who received salvage RP were excluded. Whole-body images obtained using the same device, as per the guidelines, were reviewed by two nuclear medicine specialists with more than a decade of experience to reach a consensus for each lesion. The relationships between age, PSA, Prostate Volume, clinical T stage, biopsy International Society of Urological Pathology grade (ISUP), D'amico risk group, intraprostatic tumor volume (HPTV) identified in the final histopathological specimen review, HP-ISUP grade, seminal vesicle invasion (SVI), extracapsular invasion (ECI), positive surgical margine (PSM), SUVT, SUVTLR, and SUVTPR were analyzed.

RESULTS

The mean age of the 64 included patients was 64.1 ± 5.3. A statistically significant correlation was found between SUVT, SUVTLR, SUVTPR values, and histopathologic stage parameters, such as biopsy ISUP, D'amico Risk Classification, HP-ISUP, HPTV (p < 0.05). PSMATV, SUVT, and SUVTLR were statistically significant predictors of extracapsular invasion, while PSA, PSMATV, and SUVTLR were significant predictors of SVI (p < 0.05).

CONCLUSION

The standardized SUVT, SUVTLR, and SUVTPR values could be employed as noninvasive markers to assist in predicting postoperative histopathological findings, particularly ECI, SVI, and PSM.

Prognostic Value of PSMA PET/CT in Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the majority of prostate cancer (PCa). PSMA has an enzymatic function that makes metabolic substrates such as folate available for utilization by PCa cells. Intracellular folate availability drives aggressive tumor phenotype. PSMA expression is, therefore, a marker of aggressive tumor biology. The large extracellular domain of PSMA is available for targeting by diagnostic and therapeutic radionuclides, making it a suitable cellular epitope for theranostics. PET imaging of radiolabeled PSMA ligands has several prognostic utilities. In the prebiopsy setting, intense PSMA avidity in a prostate lesion correlate well with clinically significant PCa (csPCa) on histology. When used for staging, PSMA PET imaging outperforms conventional imaging for the accurate staging of primary PCa, and findings on imaging predict post-treatment outcomes. The biggest contribution of PSMA PET imaging to PCa management is in the biochemical recurrence setting, where it has emerged as the most sensitive imaging modality for the localization of PCa recurrence by helping to guide salvage therapy. PSMA PET obtained for localizing the site of recurrence is prognostic, such that a higher lesion number predicts a less favorable outcome to salvage radiotherapy or surgical intervention. Systemic therapy is given to patients with advanced PCa with distant metastasis. PSMA PET is useful for predicting response to treatments with chemotherapy, first- and second-line androgen deprivation therapies, and PSMA-targeted radioligand therapy. Artificial intelligence using machine learning algorithms allows for the mining of information from clinical images not visible to the human eyes. Artificial intelligence applied to PSMA PET images, therefore, holds great promise for prognostication in PCa management.

The Application of Radiolabeled Targeted Molecular Probes for the Diagnosis and Treatment of Prostate Cancer

Radiopharmaceuticals targeting prostate-specific membrane antigens (PSMA) are essential for the diagnosis, evaluation, and treatment of prostate cancer (PCa), particularly metastatic castration-resistant PCa, for which conventional treatment is ineffective. These molecular probes include [⁶⁸Ga]PSMA, [¹⁸F]PSMA, [Al¹⁸F]PSMA, [^99mTc]PSMA, and [⁸⁹Zr]PSMA, which are widely used for diagnosis, and [¹⁷⁷Lu]PSMA and [²²⁵Ac]PSMA, which are used for treatment. There are also new types of radiopharmaceuticals. Due to the differentiation and heterogeneity of tumor cells, a subtype of PCa with an extremely poor prognosis, referred to as neuroendocrine prostate cancer (NEPC), has emerged, and its diagnosis and treatment present great challenges. To improve the detection rate of NEPC and prolong patient survival, many researchers have investigated the use of relevant radiopharmaceuticals as targeted molecular probes for the detection and treatment of NEPC lesions, including DOTA-TOC and DOTA-TATE for somatostatin receptors, 4A06 for CUB domain-containing protein 1, and FDG. This review focused on the specific molecular targets and various radionuclides that have been developed for PCa in recent years, including those mentioned above and several others, and aimed to provide valuable up-to-date information and research ideas for future studies.

Using PSMA imaging for prognostication in localized and advanced prostate cancer

The use of prostate-specific membrane antigen (PSMA)-directed applications in modern prostate cancer management has evolved rapidly over the past few years, helping to establish new treatment pathways and provide further insights into prostate cancer biology. However, the prognostic implications of PSMA-PET have not been studied systematically, owing to rapid clinical implementation without long follow-up periods to determine intermediate-term and long-term oncological outcomes. Currently available data suggest that traditional prognostic factors and survival outcomes are associated with high PSMA expression (both according to immunohistochemistry and PET uptake) in men with localized and biochemically recurrent disease. Treatment with curative intent (primary and/or salvage) often fails when PSMA-positive metastases are present; however, the sensitivity of PSMA-PET in detecting all metastases is poor. Low PSMA-PET uptake in recurrent disease is a favourable prognostic factor; however, it can be associated with poor prognosis in conjunction with high ¹⁸F-fluorodeoxyglucose uptake in metastatic castration-resistant prostate cancer. Clinical trials embedding PSMA-PET for guiding management with reliable oncological outcomes are needed to support ongoing clinical use.

Necessity of Pelvic Lymph Node Irradiation in Patients with Recurrent Prostate Cancer after Radical Prostatectomy in the PSMA PET/CT Era: A Narrative Review

The main prostate cancer (PCa) treatments include surgery or radiotherapy (with or without ADT). However, none of the suggested treatments eliminates the risk of lymph node metastases. Conventional imaging methods, including MRI and CT scanning, are not sensitive enough for the diagnosis of lymph node metastases; however, the novel imaging method, PSMA PET/CT scanning, has provided valuable information about the pelvic LN involvement in patients with recurrent PCa (RPCa) after radical prostatectomy. The high sensitivity and negative predictive value enable accurate N staging in PCa patients. In this narrative review, we summarize the evidence on the treatment and extent of radiation in prostate-only or whole-pelvis radiation in patients with positive and negative LN involvement on PSMA PET/CT scans.