PSMA PET total tumor volume predicts outcome of patients with advanced prostate cancer receiving [177Lu]Lu-PSMA-617 radioligand therapy in a bicentric analysis

Prostate-specific Membrane Antigen: Interpretation Criteria, Standardized Reporting, and the Use of Machine Learning

Prostate-specific membrane antigen targeting positron emission tomography (PSMA-PET) is routinely used for the staging and restaging of patients with various stages of prostate cancer. For clear communication with referring physicians and to improve inter-reader agreement, the use of standardized reporting templates is mandatory. Increasingly, tumor volume is used by reporting and response assessment frameworks to prognosticate patient outcome or measure response to therapy. However, the quantification of tumor volume is often too time-consuming in routine clinical practice. Machine learning-based tools can facilitate the quantification of tumor volume for improved outcome prognostication.

Improving sensitivity through data augmentation with synthetic lymph node metastases for AI-based analysis of PSMA PET-CT images

BACKGROUND

We developed a fully automated artificial intelligence (AI)AI-based-based method for detecting suspected lymph node metastases in prostate-specific membrane antigen (PSMA)(PSMA) positron emission tomography-computed tomography (PET-CT)(PET-CT) images of prostate cancer patients by using data augmentation that adds synthetic lymph node metastases to the images to expand the training set.

METHODS

Synthetic data were derived from original training images to which new synthetic lymph node metastases were added. Thus, the original training set from a previous study (n = 420) was expanded by one synthetic image for every original image (n = 840), which was used to train an AI model. The performance of the AI model was compared to that of nuclear medicine physicians and a previously developed AI model. The human readers were alternately used as a reference and compared to either another reading or AI model.

RESULTS

The new AI model had an average sensitivity of 84% for detecting lymph node metastases compared with 78% for human readings. Our previously developed AI method without synthetic data had an average sensitivity of 79%. The number of false positive lesions were slightly higher for the new AI model (average 3.3 instances per patient) compared to human readings and the previous AI model (average 2.8 instances per patient), while the number of false negative lesions was lower.

CONCLUSIONS

Creating synthetic lymph node metastases, as a form of data augmentation, on [18F]PSMA-1007F]PSMA-1007 PETPET-CT-CT images improved the sensitivity of an AI model for detecting suspected lymph node metastases. However, the number of false positive lesions increased somewhat.

Utility of PSMA-PET derived volumetric parameters in initial risk stratification and prediction of prostate cancer metastasis - a head-to-head comparison of the radiotracers 18F-PSMA-1007 and 68Ga-PSMA-11

OBJECTIVE

This study aimed to explore and compare the utility of baseline 18F-PSMA-1007 and 68Ga-PSMA-11 PET/computed tomography (CT) derived volumetric parameters in initial risk stratification and prediction of prostate cancer (PCa) metastasis.

METHODS

Forty treatment-naïve, biopsy-proven intermediate-/high-risk PCa patients were prospectively recruited. Each patient underwent PET/CT with 68Ga-PSMA-11 and 18F-PSMA-1007 (within 2 weeks). The maximum and mean standardized uptake values (SUVmax and SUVmean) of primary tumor, prostate PSMA-tumor volume (PSMA-TVp), and prostate total lesion PSMA (TL-PSMAp) were measured.

RESULTS

PSMA-TVp and TL-PSMAp (with both radiotracers) mostly exhibited moderate-to-strong correlation with Gleason score, serum prostate-specific antigen level and clinical tumor stage (Spearman ρ = 0.361-0.783, P-values ≤0.022). Primary tumor SUVmax values were similar across initial risk categories. PSMA-TVp and TL-PSMAp, however, were significantly higher in high-risk PCa compared to intermediate-risk PCa (P-values ≤0.001). Receiver operating characteristic (ROC) curve analysis revealed that F-PSMA-TVp, Ga-PSMA-TVp, F-TL-PSMAp, and Ga-TL-PSMAp (optimal cutoff values of 20.9, 23.4, 142.5, and 144.8, respectively) could effectively differentiate high-risk from intermediate-risk PCa [area under the ROC curve (AUCs) 0.859-0.898, P-values <0.001] with high sensitivity (~68.8-75%) and excellent specificity (100%). PSMA-TVp and TL-PSMAp (with both radiotracers) could predict presence of regional and extraregional nodal metastasis (AUCs 0.703-0.801, P-values ≤0.03) with moderate sensitivity (~47.8-70.6%) and excellent specificity (~82.6-94.1%).

CONCLUSION

Our results suggest that baseline PSMA-PET primary tumor volumetric parameters provide a noninvasive, objective, and accurate index for initial risk stratification and can predict presence of regional and extraregional nodal metastasis in PCa patients. Larger studies are warranted to evaluate their incremental role over conventional parameters.

Should new organ involvement be included in Response Evaluation Criteria in PSMA Imaging?

PURPOSE

The current study is intended to investigate the effect of new organ involvement on overall survival (OS) and modify the Response Evaluation Criteria in PSMA Imaging (RECIP) by including new organ involvement to RECIP 1.0.

MATERIALS AND METHODS

This retrospective study includes 114 patients diagnosed with metastatic castration-resistant prostate cancer (mCRPC) between September 2017 and June 2022 who had received docetaxel treatment and had baseline and post-treatment prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) images. The inclusion criteria were patients with pre- and post-treatment [18F]FDG PET/CT images and whose [18F]FDG PET images were negative. Those whose data were unavailable, who had additional malignancy, or who received abiraterone, enzalutamide, or Lutetium (Lu)-177 treatment were excluded. Age, Gleason score (GS), TPSA (total prostate-specific antigen) levels, surgical history, and OS information were recorded for each patient.

RESULTS

The 114 patients herein had a median age of 72.5 (51-91) years and a median GS of 8 (7-10). New lesions were observed in 59 patients (51.7%) and new organ PSMA uptake was observed in 14 patients (12.2%). In the multivariate Cox regression analysis, volume-based treatment response (vTR)-total lesion PSMA (TLP), RECIP PSMA-VOL, modified RECIP (mRECIP) PSMA-VOL, and mRECIP TLP were independent prognostic factors for mortality (p < 0.001, p = 0.006, p = 0.003, and p = 0.003, respectively). The median OS of patients with new organ involvement and new lesion with PSMA uptake was 9.3 months (95% CI 2.1-16.5 months) and 11.8 months (95% CI 7.4-16.2 months), respectively.

CONCLUSION

The study concluded that new organ involvement had a shorter OS than new lesion involvement. In the mRECIP that we developed, unlike RECIP, we demonstrated that both PSMA-VOL and TLP value were independent prognostic factors for mortality.

Comparison of discovery rates and prognostic utility of [68Ga]Ga-PSMA-11 PET/CT and circulating tumor DNA in prostate cancer-a cross-sectional study

BACKGROUND

Circulating-tumor DNA (ctDNA) and prostate-specific membrane antigen (PSMA) ligand positron-emission tomography (PET) enable minimal-invasive prostate cancer (PCa) detection and survival prognostication. The present study aims to compare their tumor discovery abilities and prognostic values.

METHODS

One hundred thirty men with confirmed PCa (70.5 ± 8.0 years) who underwent [68Ga]Ga-PSMA-11 PET/CT (184.8 ± 19.7 MBq) imaging and plasma sample collection (March 2019-August 2021) were included. Plasma-extracted cell-free DNA was subjected to whole-genome-based ctDNA analysis. PSMA-positive tumor lesions were delineated and their quantitative parameters extracted. ctDNA and PSMA PET/CT discovery rates were compared, and the prognostic value for overall survival (OS) was evaluated.

RESULTS

PSMA PET discovery rates according to castration status and PSA ranges did differ significantly (P = 0.013, P < 0.001), while ctDNA discovery rates did not (P = 0.311, P = 0.123). ctDNA discovery rates differed between localized and metastatic disease (P = 0.013). Correlations between ctDNA concentrations and PSMA-positive tumor volume (PSMA-TV) were significant in all (r = 0.42, P < 0.001) and castration-resistant (r = 0.65, P < 0.001), however not in hormone-sensitive patients (r = 0.15, P = 0.249). PSMA-TV and ctDNA levels were associated with survival outcomes in the Logrank (P < 0.0001, P < 0.0001) and multivariate Cox regression analysis (P = 0.0023, P < 0.0001).

CONCLUSION

These findings suggest that PSMA PET imaging outperforms ctDNA analysis in detecting prostate cancer across the whole spectrum of disease, while both modalities are independently highly prognostic for survival outcomes.

PSMA-Targeted Radiopharmaceuticals for Prostate Cancer Diagnosis and Therapy

ABSTRACT

Prostate cancer (PCa) is the most common noncutaneous malignancy in men. Until recent years, accurate imaging of men with newly diagnosed PCa, or recurrent or low-volume metastatic disease, was limited. Further, therapeutic options for men with advanced, metastatic, castration-resistant disease were increasingly limited as a result of increasing numbers of systemic therapies being combined in the upfront metastatic setting. The advent of urea-based, small-molecule inhibitors of prostate-specific membrane antigen (PSMA) has partially addressed those shortcomings in diagnosis and therapy of PCa. On the diagnostic side, there are multiple pivotal phase III trials with several different agents having demonstrated utility in the initial staging setting, with generally modest sensitivity but very high specificity for determining otherwise-occult pelvic nodal involvement. That latter statistic drives the utility of the scan by allowing imaging interpreters to read with very high sensitivity while maintaining a robust specificity. Other pivotal phase III trials have demonstrated high detection efficiency in patients with biochemical failure, with high positive predictive value at the lesion level, opening up possible new avenues of therapy such as metastasis-directed therapy. Beyond the diagnostic aspects of PSMA-targeted radiotracers, the same urea-based chemical scaffolds can be altered to deliver therapeutic isotopes to PCa cells that express PSMA. To date, one such agent, when combined with best standard-of-care therapy, has demonstrated an ability to improve overall survival, progression-free survival, and freedom from skeletal events relative to best standard-of-care therapy alone in men with metastatic, castration-resistant PCa who are post chemotherapy. Within the current milieu, there are a number of important future directions including the use of artificial intelligence to better leverage diagnostic findings, further medicinal chemistry refinements to the urea-based structure that may allow improved tumor targeting and decreased toxicities, and the incorporation of new radionuclides that may better balance efficacy with toxicities than those nuclides that are available.

Advances in PSMA Alpha Theragnostics

Alpha theranostics offer an attractive alternative form of therapy, which has best been investigated and documented with 225Ac-PSMA in patients with prostate cancer. Advantages offered by targeted alpha therapy include overcoming radiation resistance, oxygen independence, effecting double-stranded DNA breakages within the tumors with anticipated improved clinical outcomes and an acceptable side effect profile. The previous Seminars article on this topic, published in 2020, had to rely mostly on published case reports and small observational studies. In the last few years, however, several meta-analyses have emerged that evaluate the safety and efficacy of 225Ac-PSMA in prostate cancer patients, followed most recently by a multi-center retrospective study initiated by WARMTH. The findings of these publications, together with the exploration of TAT offered in clinical conditions other than as a last resort, is the focus of this updated overview. Unresolved clinical issues that remain, include the appropriate selection of patients that would benefit most from treatment with 225Ac-PSMA, treatment timing within the disease landscape, optimal dosing schedule, dosimetry, when and how to best use combination therapies and minimization and treatment of side effects, particularly that of xerostomia.

Same-day post-therapy imaging with a new generation whole-body digital SPECT/CT in assessing treatment response to [177Lu]Lu-PSMA-617 in metastatic castration-resistant prostate cancer

PURPOSE

Lutetium-177 [177Lu]Lu-PSMA-617 radioligand therapy (RLT) represents a significant advancement for metastatic castration-resistant prostate cancer (mCRPC), demonstrating improvements in radiographic progression free survival (rPFS) and overall survival (OS) with a low rate of associated side effects. Currently, most post-therapy SPECT/CT is conducted at 24 h after infusion. This study examines the clinical utility of a next-generation multi-detector Cadmium-Zinc-Telluride (CZT) SPECT/CT system (StarGuide) in same-day post-infusion assessment and early treatment response to [177Lu]Lu-PSMA-617.

METHODS

In this retrospective study, 68 men with progressive mCRPC treated with [177Lu]Lu-PSMA-617 at our center from June 2022 to June 2023 were evaluated. Digital whole-body SPECT/CT imaging was performed after [177Lu]Lu-PSMA-617infusion (mean ± SD: 1.8 ± 0.6 h, range 1.1-4.9 h). Quantitative analysis of [177Lu]Lu-PSMA-617 positive lesions was performed in patients who underwent at least 2 post-therapy SPECT/CT, using liver parenchyma uptake as reference. Metrics including [177Lu]Lu-PSMA-617 positive total tumor volume (Lu-TTV), SUVmax and SUVmean were calculated. These quantitative metrics on post-infusion SPECT/CT images after cycles 1, 2 and 3 were correlated with overall survival (OS), prostate specific antigen-progression free survival (PSA-PFS) as defined by prostate cancer working group 3 (PCWG3), and PSA decrease over 50% (PSA50) response rates.

RESULTS

56 patients (means age 76.2 ± 8.1 years, range: 60-93) who underwent at least 2 post-therapy SPECT/CT were included in the image analysis. The whole-body SPECT/CT scans (~ 12 min per scan) were well tolerated, with 221 same-day scans performed (89%). At a median of 10-months follow-up, 33 (58.9%) patients achieved PSA50 after [177Lu]Lu-PSMA-617 treatment and median PSA-PFS was 5.0 months (range: 1.0-15 months) while median OS was not reached. Quantitative analysis of SPECT/CT images showed that 37 patients (66%) had > 30% reduction in Lu-TTV, associated with significantly improved overall survival (median not reached vs. 6 months, P = 0.008) and PSA-PFS (median 6 months vs. 1 months, P < 0.001). However, changes in SUVmax or SUVmean did not correlate with PSA-PFS or OS.

CONCLUSION

We successfully implemented same-day post-therapy SPECT/CT after [177Lu]Lu-PSMA-617 infusions. Quantitation of 1-2 h post-therapy SPECT/CT images is a promising method for assessing treatment response. However, the approach is currently limited by its suboptimal detection of small tumor lesions and the necessity of incorporating a third-cycle SPECT/CT to mitigate the effects of any potential treatment-related flare-up. Further investigation in a larger patient cohort and prospective validation is essential to confirm these findings and to explore the role of SPECT/CT as a potential adjunct to PSMA PET/CT in managing mCRPC.

Prostate Cancer Theranostics With 177Lu-PSMA

This review paper highlights the transformative role of PSMA-targeted diagnostics and therapy in prostate cancer management, particularly focusing on 177Lu-PSMA-617, approved by the FDA and EMA for metastatic castration-resistant prostate cancer (mCRPC) patients post-chemotherapy and ARPI treatment. Originating from the VISION trial's success, this paper navigates the current radioligand therapy (RLT) indications, emphasizing practical patient selection, planning, and treatment execution. It critically examines Lu-PSMA's comparative effectiveness against cabazitaxel and Ra-223, addressing decision-making dilemmas for mCRPC treatments. Furthermore, the paper discusses Lu-PSMA in chemotherapy-naïve patients and its application in hormone-sensitive prostate cancer, underlined by ongoing global studies. A significant concern is Lu-PSMA's long-term safety profile, particularly nephrotoxicity risks, necessitating further investigation. The possibility of Lu-PSMA rechallenge in responsive patients is explored, stressing the need for comprehensive analyses and real-world data to refine treatment protocols. Conclusively, PSMA-targeted therapy marks a significant advance in prostate cancer therapy, advocating for its integration into a multimodal, patient-centric treatment approach. The review underscores the imperative for additional comparative studies to optimize treatment sequences and outcomes, ultimately enhancing long-term prognosis and disease control in prostate cancer management.

177Lu-PSMA therapy in metastatic prostate cancer: An updated review of prognostic and predictive biomarkers

177Lu-PSMA has been approved for the treatment of PSMA-positive metastatic castration-resistant (mCRPC) patients who progressed to androgen receptor pathway inhibitors (ARPIs) and taxane-based chemotherapy. However, a higher proportion of patients do not respond to this type of radioligand therapy (RLT). To date, there is a lack of validated prognostic and predictive biomarkers for 177Lu-PSMA therapy in prostate cancer. Several studies have investigated the prognostic and predictive role of clinical and molecular factors and also the metabolic features of PET imaging. In this review, we aim to take stock of the current scenario, focusing on new emerging data from retrospective/prospective series and clinical trials. Given the high costs and the possibility of primary resistance, it seems essential to identify clinical and molecular characteristics that could allow clinicians to choose the right patient to treat with 177Lu-PSMA. Biomarker-based clinical trials are urgently needed in this field.

Prostate-Specific Membrane Antigen-Targeted Therapies for Prostate Cancer: Towards Improving Therapeutic Outcomes

CONTEXT

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein overexpressed in most prostate cancers and exploited as a target for PSMA-targeted therapies. Different approaches to target PSMA-expressing cancer cells have been developed, showing promising results in clinical trials.

OBJECTIVE

To discuss the regulation of PSMA expression and the main PSMA-targeted therapeutic concepts illustrating their clinical development and rationalizing combination approaches with examples.

EVIDENCE ACQUISITION

We performed a detailed literature search using PubMed and reviewed the American Society of Clinical Oncology and European Society of Medical Oncology annual meeting abstracts up to September 2023.

EVIDENCE SYNTHESIS

We present an overarching description of the different strategies to target PSMA. The outcomes of PSMA-targeted therapies strongly rely on surface-bound PSMA expression. However, PSMA heterogeneity at different levels (interpatient and inter/intratumoral) limits the efficacy of PSMA-targeted therapies. We highlight the molecular mechanisms governing PSMA regulation, the understanding of which is crucial to designing therapeutic strategies aimed at upregulating PSMA expression. Thus far, homeobox B13 (HOXB13) and androgen receptor (AR) have emerged as critical transcription factors positively and negatively regulating PSMA expression, respectively. Furthermore, epigenetic regulation of PSMA has been also reported recently. In addition, many established therapeutic approaches harbor the potential to upregulate PSMA levels as well as potentiate DNA damage mediated by current radioligands.

CONCLUSIONS

PSMA-targeted therapies are rapidly advancing, but their efficacy is strongly limited by the heterogeneous expression of the target. A thorough comprehension of how PSMA is regulated will help improve the outcomes through increasing PSMA expression and will provide the basis for synergistic combination therapies.

PATIENT SUMMARY

Prostate-specific membrane antigen (PSMA) is overexpressed in most prostate cancers. PSMA-targeted therapies have shown promising results, but the heterogeneous expression of PSMA limits their efficacy. We propose to better elucidate the regulation of PSMA expression to increase the levels of the target and improve the therapeutic outcomes.

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.

Change in total lesion PSMA (TLP) during [177Lu]Lu-PSMA-617 radioligand therapy predicts overall survival in patients with mCRPC: monocentric evaluation of a prospective registry

PURPOSE

This study investigates imaging response of [177Lu]Lu-PSMA-617 radioligand therapy (RLT) based on the whole-body parameter total lesion PSMA (TLP), derived by PSMA-PET/CT and reflecting the total tumor burden, in patients with metastatic castration-resistant prostate cancer (mCRPC) enrolled in a prospective registry (NCT04833517).

METHODS

A total of n = 102 mCRPC patients received a [68Ga]Ga-PSMA-11 PET/CT at baseline and after two cycles of PSMA-RLT, in which TLP was measured by using a semi-automated tumor segmentation. TLP was defined as the summed products of volume and uptake (∑ Volume × SUVmean) of all tumor lesions. The Kaplan-Meier method was used to determine the most appropriate ∆TLP thresholds for classification into partial remission (PR), stable disease (SD), and progressive disease (PD) regarding overall survival (OS). Furthermore, we analyzed criteria that are also frequently used in established response frameworks, such as the occurrence of new metastases as independent criterion (I) or in combination with change in tumor burden (II), and the change in PSA serum value (III).

RESULTS

For the ∆TLP thresholds -30%/+30% (and also for higher thresholds, -40%/+40% or -50%/+50%), significant differences between all three response categories became apparent (PR/PD: p = 0.001; PR/SD: p = 0.001; SD/PD: p = 0.018). Including the development of new metastases as independent criterion of PD, there was no significant difference in OS between SD and PD (p = 0.455), neither when applied in combination with TLP (p = 0.191). Similarly, significant differentiation between SD and PD was not achieved by PSA serum value (p = 0.973).

CONCLUSION

In the largest monocentric study to date, TLP is shown to be a qualified prognostic biomarker, applying ∆TLP thresholds of -30%/+30%. It significantly differentiated between PR, SD, and PD, whereas other response criteria did not differentiate SD vs. PD. Using TLP, the development of new metastases is not a required information for predicting OS.

PSMA-Hornet: Fully-automated, multi-target segmentation of healthy organs in PSMA PET/CT images

BACKGROUND

Prostate-specific membrane antigen (PSMA) PET imaging represents a valuable source of information reflecting disease stage, response rate, and treatment optimization options, particularly with PSMA radioligand therapy. Quantification of radiopharmaceutical uptake in healthy organs from PSMA images has the potential to minimize toxicity by extrapolation of the radiation dose delivery towards personalization of therapy. However, segmentation and quantification of uptake in organs requires labor-intensive organ delineations that are often not feasible in the clinic nor scalable for large clinical trials.

PURPOSE

In this work we develop and test the PSMA Healthy organ segmentation network (PSMA-Hornet), a fully-automated deep neural net for simultaneous segmentation of 14 healthy organs representing the normal biodistribution of [18 F]DCFPyL on PET/CT images. We also propose a modified U-net architecture, a self-supervised pre-training method for PET/CT images, a multi-target Dice loss, and multi-target batch balancing to effectively train PSMA-Hornet and similar networks.

METHODS

The study used manually-segmented [18 F]DCFPyL PET/CT images from 100 subjects, and 526 similar images without segmentations. The unsegmented images were used for self-supervised model pretraining. For supervised training, Monte-Carlo cross-validation was used to evaluate the network performance, with 85 subjects in each trial reserved for model training, 5 for validation, and 10 for testing. Image segmentation and quantification metrics were evaluated on the test folds with respect to manual segmentations by a nuclear medicine physician, and compared to inter-rater agreement. The model's segmentation performance was also evaluated on a separate set of 19 images with high tumor load.

RESULTS

With our best model, the lowest mean Dice coefficient on the test set was 0.826 for the sublingual gland, and the highest was 0.964 for liver. The highest mean error in tracer uptake quantification was 13.9% in the sublingual gland. Self-supervised pretraining improved training convergence, train-to-test generalization, and segmentation quality. In addition, we found that a multi-target network produced significantly higher segmentation accuracy than single-organ networks.

CONCLUSIONS

The developed network can be used to automatically obtain high-quality organ segmentations for PSMA image analysis tasks. It can be used to reproducibly extract imaging data, and holds promise for clinical applications such as personalized radiation dosimetry and improved radioligand therapy.

Prostate-Specific Membrane Antigen: Gateway to Management of Advanced Prostate Cancer

Prostate-specific membrane antigen (PSMA) as a transmembrane protein is overexpressed by prostate cancer (PC) cells and is accessible for binding antibodies or low-molecular-weight radioligands due to its extracellular portion. Successful targeting of PSMA began with the development of humanized J591 antibody. Due to their faster clearance compared to antibodies, small-molecule radioligands for targeted imaging and therapy of PC have been favored in recent development efforts. PSMA positron emission tomography (PET) imaging has higher diagnostic performance than conventional imaging for initial staging of high-risk PC and biochemical recurrence detection/localization. However, it remains to be demonstrated how to integrate PSMA PET imaging for therapy response assessment and as an outcome endpoint measure in clinical trials. With the recent approval of 177Lu-PSMA-617 by the US Food and Drug Administration for metastatic castration-resistant PC progressing after chemotherapy, the high value of PSMA-targeted therapy was confirmed. Compared to standard of care, PSMA-based radioligand therapy led to a better outcome and a higher quality of life. This review, focusing on the advanced PC setting, provides an overview of different approved and nonapproved PSMA-targeted imaging and therapeutic modalities and discusses the future of PSMA-targeted theranostics, also with an outlook on non-radiopharmaceutical-based PSMA-targeted therapies.

Radiomics and Artificial Intelligence in Radiotheranostics: A Review of Applications for Radioligands Targeting Somatostatin Receptors and Prostate-Specific Membrane Antigens

Radiotheranostics refers to the pairing of radioactive imaging biomarkers with radioactive therapeutic compounds that deliver ionizing radiation. Given the introduction of very promising radiopharmaceuticals, the radiotheranostics approach is creating a novel paradigm in personalized, targeted radionuclide therapies (TRTs), also known as radiopharmaceuticals (RPTs). Radiotherapeutic pairs targeting somatostatin receptors (SSTR) and prostate-specific membrane antigens (PSMA) are increasingly being used to diagnose and treat patients with metastatic neuroendocrine tumors (NETs) and prostate cancer. In parallel, radiomics and artificial intelligence (AI), as important areas in quantitative image analysis, are paving the way for significantly enhanced workflows in diagnostic and theranostic fields, from data and image processing to clinical decision support, improving patient selection, personalized treatment strategies, response prediction, and prognostication. Furthermore, AI has the potential for tremendous effectiveness in patient dosimetry which copes with complex and time-consuming tasks in the RPT workflow. The present work provides a comprehensive overview of radiomics and AI application in radiotheranostics, focusing on pairs of SSTR- or PSMA-targeting radioligands, describing the fundamental concepts and specific imaging/treatment features. Our review includes ligands radiolabeled by 68Ga, 18F, 177Lu, 64Cu, 90Y, and 225Ac. Specifically, contributions via radiomics and AI towards improved image acquisition, reconstruction, treatment response, segmentation, restaging, lesion classification, dose prediction, and estimation as well as ongoing developments and future directions are discussed.

Prostate-Specific Membrane Antigen-Ligand Therapy: What the Radiologist Needs to Know

The discovery and clinical development of radiolabeled small-molecule ligands targeting prostate-specific membrane antigen (PSMA) has had a profound influence on the field of nuclear medicine. Such agents have been successfully deployed for both imaging and therapeutic applications. In particular, PSMA radioligand therapy (PRLT) has been shown to be a life-prolonging therapy for men with metastatic, castration-resistant prostate cancer and has also brought nuclear medicine physicians and nuclear radiologists into the forefront of direct patient care. In this review, we will discuss the clinical study data regarding the efficacy and toxicities related to PRLT, outline the key personnel that any center offering PRLT should have, offer salient clinical examples, and provide an overview of future directions for PRLT. As PRLT continues to evolve as a treatment modality, it is paramount that nuclear medicine physicians and nuclear radiologists understand the clinical context, management implications, and practical aspects so as to best deliver high-value care to patients.

Standardized PSMA-PET Imaging of Advanced Prostate Cancer

Imaging of advanced prostate cancer is a challenging task, as it requires longitudinal characterization of disease extent in a standardized way to enable appropriate treatment selection and evaluation of treatment efficacy. In the last years, prostate-specific membrane antigen (PSMA)-PET/CT has become the reference standard examination for patients with advanced prostate cancer. Together with the rise of PSMA-PET, standardized frameworks for the reporting of image findings have been proposed, eg, the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) and the structured reporting system for PSMA targeted PET imaging (PSMA-RADS) framework. Therefore, recent evidence on PSMA-PET derived tumor volume as useful a biomarker for outcome prognostication and related frameworks will be discussed in the article. The PROMISE framework recommends quantifying the tumor volume per-organ system, which accounts for the fact that the location of the metastases greatly influence its biological aggressiveness. In addition, changes in PSMA-PET derived tumor volume have been shown to be promising biomarkers for response assessment. Limitations of PSMA-PET will also be discussed because the tumor volume might not always be suited for response assessment. As a pitfall of PSMA-based systems, decreasing PSMA-expression might erroneously be interpreted as response to therapy. Also, especially for patients with limited disease, the tumor volume might not be ideal for response assessment. Therefore, various frameworks have been introduced to objectively measure response to therapy with PSMA-PET. Amongst these, the PSMA-PET progression (PPP) criteria and the response evaluation criteria in PSMA (RECIP) are optimized for earlier and later phenotypes of advanced prostate cancer, respectively. Variables needed to determine PPP or RECIP outcome on PSMA-PET are recorded under the umbrella of PROMISE recommendations. In this article, various reporting and response assessment frameworks are explained and discussed. Also, recent evidence for the relevance of PSMA-PET biomarkers for clinical management and outcome prognostication are shown.

Comparison of parametric imaging and SUV imaging with [68 Ga]Ga-PSMA-11 using dynamic total-body PET/CT in prostate cancer

PURPOSE

Standardized uptake value (SUV) has been prevalently used to measure [68 Ga]Ga-PSMA-11 activity in prostate cancer, but it is susceptible to multiple factors. Parametric imaging allows for absolute quantification of tracer uptake and provides a better diagnostic accuracy that is crucial for lesion detection. However, the clinical significance of total-body parametric imaging of [68 Ga]Ga-PSMA-11 remains to be fully assessed. Therefore, the aim of our study is to delve into the diagnostic implications of total-body parametric imaging of [68 Ga]Ga-PSMA-11 PET/CT for patients with prostate cancer.

METHODS

Twenty prostate cancer patients were included and underwent a dynamic total-body [68 Ga]Ga-PSMA-11 PET/CT scan. An irreversible two-tissue compartment model (2T3k) was fitted for each tissue time-to-activity curve, and the net influx rate (Ki) was obtained. The image quality and semi-quantitative analysis of lesion-to-background ratio (LBR), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were compared between parametric images and SUV images.

RESULTS

Kinetic modeling using 2T3k demonstrated favorable model fitting in both normal organs and lesions. All of the lesions detected on SUV images (55-60 min) could be detected on Ki images. The correlation between Ki, SUVmean, and SUVmax in both normal organs and pathological lesions was found to be positive and statistically significant. Conversely, a moderate positive correlations were found between Ki and K1 (R = 0.69, P < 0.001; R = 0.61, P < 0.001) and Ki and k3 (R = 0.69, P < 0.001; R = 0.62, P < 0.001), in normal organs and pathological lesions, respectively. Visual assessment in Ki images showed less image noise and higher lesions conspicuity compared to SUV images. Ki image-derived LBR, SNR, and CBR of pathological lesions including primary tumors (PTs), lymph node metastases (LNMs) and bone metastases (BMs), exhibited remarkably higher folds (1.4-3.6 folds) compared to those derived from SUV of corresponding lesions.

CONCLUSIONS

Total-body parametric imaging of [68 Ga]Ga-PSMA-11 enhanced lesion contrast and improved lesion detectability compared to SUV images. This may potentially serve as an imaging biomarker and theranostic tool for precise diagnosis and treatment evaluation in prostate cancer patients.

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.

Applications of Artificial Intelligence in PSMA PET/CT for Prostate Cancer Imaging

Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) has emerged as an important imaging technique for prostate cancer. The use of PSMA PET/CT is rapidly increasing, while the number of nuclear medicine physicians and radiologists to interpret these scans is limited. Additionally, there is variability in interpretation among readers. Artificial intelligence techniques, including traditional machine learning and deep learning algorithms, are being used to address these challenges and provide additional insights from the images. The aim of this scoping review was to summarize the available research on the development and applications of AI in PSMA PET/CT for prostate cancer imaging. A systematic literature search was performed in PubMed, Embase and Cinahl according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 26 publications were included in the synthesis. The included studies focus on different aspects of artificial intelligence in PSMA PET/CT, including detection of primary tumor, local recurrence and metastatic lesions, lesion classification, tumor quantification and prediction/prognostication. Several studies show similar performances of artificial intelligence algorithms compared to human interpretation. Few artificial intelligence tools are approved for use in clinical practice. Major limitations include the lack of external validation and prospective design. Demonstrating the clinical impact and utility of artificial intelligence tools is crucial for their adoption in healthcare settings. To take the next step towards a clinically valuable artificial intelligence tool that provides quantitative data, independent validation studies are needed across institutions and equipment to ensure robustness.

SUVmean on baseline [18F]PSMA-1007 PET and clinical parameters are associated with survival in prostate cancer patients scheduled for [177Lu]Lu-PSMA I&T

BACKGROUND

Quantification of [68 Ga]-labeled PSMA PET predicts response in patients with prostate cancer (PC) who undergo PSMA-targeted radioligand therapy (RLT). Given the increasing use [18F]-labeled radiotracers, we aimed to determine whether the uptake derived from [18F]PSMA-1007 PET can also identify responders and to assess its prognostic value relative to established clinical parameters.

METHODS

We retrospectively analyzed 103 patients with metastatic, castration-resistant PC who were treated with [177Lu]Lu-PSMA I&T. We calculated SUVmean, SUVmax, PSMA-avid tumor volume (TV), and total lesion PSMA (defined as PSMA-TV*SUVmean) on pre-therapeutic [18F]PSMA-1007 PET. Laboratory values for hemoglobin, C-reactive protein (CRP), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alkaline phosphatase (AP) were also collected prior to RLT. We performed univariable Cox regression followed by multivariable and Kaplan-Meier analyses with overall survival (OS) serving as endpoint. Last, we also computed a risk factor (RF) model including all items reaching significance on multivariable analysis to determine whether an increasing number of RFs can improve risk stratification.

RESULTS

A total of 48 patients died and median OS was 16 months. On univariable Cox regression, SUVmean, CRP, LDH, hemoglobin, and the presence of liver metastases were significantly associated with OS. On multivariable Cox regression, the following significant prognostic factors for OS were identified: SUVmean (per unit, HR, 0.91; P = 0.04), the presence of liver metastases (HR, 2.37; P = 0.03), CRP (per mg/dl, HR, 1.13; P = 0.003), and hemoglobin (per g/dl, HR, 0.76; P < 0.01). Kaplan-Meier analysis showed significant separation between patients with a SUVmean below or above a median SUVmean of 9.4 (9 vs 19 months, HR 0.57; P = 0.03). Of note, patients with only one RF (median OS not reached) showed longest survival compared to patients with two (11 months; HR 2.43 95% CI 1.07-5.49, P = 0.02) or more than two RFs (7 months; HR 3.37 95% CI 1.62-7.03, P < 0.001).

CONCLUSION

A lower SUVmean derived from [18F]PSMA-1007, higher CRP, lower hemoglobin, and the presence of liver metastases are associated with reduced OS in patients undergoing RLT. An early RF model also demonstrated that an increasing number of those factors is linked to worse outcome, thereby emphasizing the importance of clinical and imaging parameters for adequate risk stratification.

Role of volumetric parameters obtained from 68 Ga-PSMA PET/CT and 18F-FDG PET/CT in predicting overall survival in patients with mCRPC receiving taxane therapy

OBJECTIVE

The aim of this study was to determine the prognostic role of volumetric parameters and Pro-PET scores obtained from 68 Ga-prostate-specific membrane antigen (PSMA) PET/CT and 18F-FDG PET/CT in patients with metastatic castration-resistant prostate cancer (mCRPC) receiving taxane therapy.

MATERIALS AND METHODS

The study included 71 patients who underwent simultaneous PSMA and 18F-FDG PET/CT imaging between January 2019 and January 2022, had a Pro-PET score of 3-5 and had received taxane therapy after imaging. 18F-FDG tumor volume (TV-F) and PSMA tumor volume (TV-P) values of the lesions and total lesion glycolysis (TL-G) and total lesion PSMA (TL-P) values of the lesions were calculated on both imaging studies and the effects of these parameters on overall survival (OS) were investigated.

RESULTS

The median age of the patients included herein was 71 years (56-89) and the median prostate-specific antigen (PSA) level was 16.4 (0.01-1852 ng/dL). According to the Kaplan-Meier survival analysis, TTV-P ≥ 78.5, TTL-P ≥ 278.8, TTV-F ≥ 94.98, TTL-G ≥ 458.3, TTV-P + F ≥ 195.45, TTL-G + P ≥ 855.78, lymph node (L)TV-FDG ≥ 3.4, LFDG-SUVmax ≥ 3.2, LFDG-SUVmean ≥ 2.25, LFDG-SUVpeak ≥ 2.55, and bone (B)TV-F ≥ 51.15 values were found to be prognostic factors in predicting short OS. Multivariate Cox regression analysis showed that a Vscore ≥ 3 (95% confidence interval [CI]: 7.069-98.251, p < 0.001) and TTL-G + P ≥ 855.78 (95% CI: 4.878-1037.860, p = 0.006) were found to be independent prognostic factors in predicting short OS.

CONCLUSION

Volumetric parameters and Pro-PET scores obtained from 68 Ga-PSMA PET/CT and 18F-FDG PET/CT imaging have been shown to have an impact on OS in patients with mCRPC receiving taxane therapy.

Is There a Role of Artificial Intelligence in Preclinical Imaging?

This review provides an overview of the current opportunities for integrating artificial intelligence methods into the field of preclinical imaging research in nuclear medicine. The growing demand for imaging agents and therapeutics that are adapted to specific tumor phenotypes can be excellently served by the evolving multiple capabilities of molecular imaging and theranostics. However, the increasing demand for rapid development of novel, specific radioligands with minimal side effects that excel in diagnostic imaging and achieve significant therapeutic effects requires a challenging preclinical pipeline: from target identification through chemical, physical, and biological development to the conduct of clinical trials, coupled with dosimetry and various pre, interim, and post-treatment staging images to create a translational feedback loop for evaluating the efficacy of diagnostic or therapeutic ligands. In virtually all areas of this pipeline, the use of artificial intelligence and in particular deep-learning systems such as neural networks could not only address the above-mentioned challenges, but also provide insights that would not have been possible without their use. In the future, we expect that not only the clinical aspects of nuclear medicine will be supported by artificial intelligence, but that there will also be a general shift toward artificial intelligence-assisted in silico research that will address the increasingly complex nature of identifying targets for cancer patients and developing radioligands.

PSMA-targeted therapy for non-prostate cancers

Radioligand therapy (RLT) agents are demonstrating a crucial role in the clinical approach to aggressive malignancies such as metastatic castrate-resistant prostate cancer (m-CRPC). With the recent FDA approval of prostate-specific membrane antigen (PSMA)-targeted RLT for m-CRPC, the field has broadened its gaze to explore other cancers that express PSMA in the tumor parenchyma or tumor neovasculature. In this review article, we discuss current progress in the clinical use of PSMA RLTs in non-prostate cancers such salivary gland cancers, renal cell carcinoma, high grade glioma, and soft tissue sarcoma. We highlight early reports in small case series and clinical trials indicating promise for PSMA-targeted RLT and highlighting the importance of identifying patient cohorts who may most benefit from these interventions. Further study is indicated in non-prostate cancers investigating PSMA RLT dosimetry, PSMA PET/CT imaging as a biomarker, and assessing PSMA RLT safety and efficacy in these cancers.

Tumor Volume on PSMA PET as a Prognostic Biomarker in Prostate Cancer Patients Treated With Cabazitaxel

PURPOSE

The aim of this study was to evaluate the prognostic value of 68Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT in metastatic castration-resistant prostate cancer patients receiving second-line chemotherapy with cabazitaxel.

METHODS

All patients with metastatic castration-resistant prostate cancer who underwent a PSMA PET/CT within 8 weeks before initiating the cabazitaxel treatment were retrospectively evaluated. The whole-body PSMA total tumor volume (PSMA-TV) was measured for each patient. Other factors such as prostate-specific antigen, hemoglobin, lactate dehydrogenase, and alkaline phosphatase were recorded. A log-rank cutoff finder was used to define the PSMA-TV optimal cutoff. Survival analyses were performed using Cox regression and Kaplan-Meier methods.

RESULTS

In total, 32 patients were included, receiving a median of 6 cycles of cabazitaxel (range, 2-10). After a median follow-up of 12 months, 28 patients presented disease progression, and 18 died. Baseline PSMA-TV presented a significant association with progression-free survival (PFS) and overall survival (OS; P = 0.035 and P = 0.002, respectively). Optimal PSMA-TV cutoffs were 515 mL for PFS and 473 mL for OS. Patients with low volume presented longer PFS and OS than those with high volume: median PFS, 21 versus 12 weeks, respectively (hazard ratio, 0.33; P = 0.017); and median OS, 24 versus 8.5 months, respectively (hazard ratio, 0.21; P = 0.002). On the multivariable analyses, PSMA-TV remained an independent predictor of OS (P = 0.016).

CONCLUSION

Our results show that total tumor volume measured on PSMA PET/CT is a prognostic biomarker in patients treated with cabazitaxel. High PSMA-TV before treatment initiation is associated with shorter PFS and OS.

Predicting the effect of different folate doses on [68Ga]Ga-PSMA-11 organ and tumor uptake using physiologically based pharmacokinetic modeling

BACKGROUND

Folate intake might reduce [⁶⁸Ga]Ga-PSMA-11 uptake in tissues due to a competitive binding to the PSMA receptor. For diagnostic imaging, this could impact decision making, while during radioligand therapy this could affect treatment efficacy. The relationship between folate dose, timing of dosing and tumor and organ uptake is not well established. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model to predict the effect of folates on [⁶⁸Ga]Ga-PSMA-11 PET/CT uptake in salivary glands, kidneys and tumors.

METHODS

A PBPK model was developed for [⁶⁸Ga]Ga-PSMA-11 and folates (folic acid and its metabolite 5-MTHF), with compartments added that represent salivary glands and tumor. Reactions describing receptor binding, internalization and intracellular degradation were included. Model evaluation for [⁶⁸Ga]Ga-PSMA-11 was performed by using patient scan data from two different studies (static and dynamic), while for folates data from the literature were used for evaluation. Simulations were performed to assess the effect of different folate doses (150 µg, 400 µg, 5 mg and 10 mg) on accumulation in salivary glands, kidney and tumor, also for patients with different tumor volumes (10, 100, 500 and 1000 mL).

RESULTS

Final model evaluation showed that predictions adequately described data for both [⁶⁸Ga]Ga-PSMA-11 and folates. Predictions of a 5-MTFH dose of 150 µg and folic acid dose of 400 µg (in case of administration at the same time as [⁶⁸Ga]Ga-PSMA-11 (t = 0)) showed no clinically relevant effect on salivary glands and kidney uptake. However, the effect of a decrease in salivary glands and kidney uptake was determined to be clinically relevant for doses of 5 mg (34% decrease for salivary glands and 32% decrease for kidney) and 10 mg (36% decrease for salivary glands and 34% decrease for kidney). Predictions showed that tumor uptake was not relevantly affected by the co-administration of folate for all different folate doses (range 150 µg-10 mg). Lastly, different tumor volumes did not impact the folate effect on [⁶⁸Ga]Ga-PSMA-11 biodistribution.

CONCLUSION

Using a PBPK model approach, high doses of folate (5 and 10 mg) were predicted to show a decrease of [⁶⁸Ga]Ga-PSMA-11 salivary glands and kidney uptake, while intake by means of folate containing food or vitamin supplements showed no relevant effects. In addition, tumor uptake was not affected by folate administration in the simulated dose ranges (150 µg-10 mg). Differences in tumor volume are not expected to impact folate effects on [⁶⁸Ga]Ga-PSMA-11 organ uptake.

Novel computational biology modeling system can accurately forecast response to neoadjuvant therapy in early breast cancer

BACKGROUND

Generalizable population-based studies are unable to account for individual tumor heterogeneity that contributes to variability in a patient's response to physician-chosen therapy. Although molecular characterization of tumors has advanced precision medicine, in early-stage and locally advanced breast cancer patients, predicting a patient's response to neoadjuvant therapy (NAT) remains a gap in current clinical practice. Here, we perform a study in an independent cohort of early-stage and locally advanced breast cancer patients to forecast tumor response to NAT and assess the stability of a previously validated biophysical simulation platform.

METHODS

A single-blinded study was performed using a retrospective database from a single institution (9/2014-12/2020). Patients included: ≥ 18 years with breast cancer who completed NAT, with pre-treatment dynamic contrast enhanced magnetic resonance imaging. Demographics, chemotherapy, baseline (pre-treatment) MRI and pathologic data were input into the TumorScope Predict (TS) biophysical simulation platform to generate predictions. Primary outcomes included predictions of pathological complete response (pCR) versus residual disease (RD) and final volume for each tumor. For validation, post-NAT predicted pCR and tumor volumes were compared to actual pathological assessment and MRI-assessed volumes. Predicted pCR was pre-defined as residual tumor volume ≤ 0.01 cm³ (≥ 99.9% reduction).

RESULTS

The cohort consisted of eighty patients; 36 Caucasian and 40 African American. Most tumors were high-grade (54.4% grade 3) invasive ductal carcinomas (90.0%). Receptor subtypes included hormone receptor positive (HR+)/human epidermal growth factor receptor 2 positive (HER2+, 30%), HR+/HER2- (35%), HR-/HER2+ (12.5%) and triple negative breast cancer (TNBC, 22.5%). Simulated tumor volume was significantly correlated with post-treatment radiographic MRI calculated volumes (r = 0.53, p = 1.3 × 10^-7, mean absolute error of 6.57%). TS prediction of pCR compared favorably to pathological assessment (pCR: TS n = 28; Path n = 27; RD: TS n = 52; Path n = 53), for an overall accuracy of 91.2% (95% CI: 82.8% - 96.4%; Clopper-Pearson interval). Five-year risk of recurrence demonstrated similar prognostic performance between TS predictions (Hazard ratio (HR): - 1.99; 95% CI [- 3.96, - 0.02]; p = 0.043) and clinically assessed pCR (HR: - 1.76; 95% CI [- 3.75, 0.23]; p = 0.054).

CONCLUSION

We demonstrated TS ability to simulate and model tumor in vivo conditions in silico and forecast volume response to NAT across breast tumor subtypes.

A Prognostic Risk Score for Prostate Cancer Based on PSMA PET-derived Organ-specific Tumor Volumes

Background Prostate-specific membrane antigen (PSMA) PET has high specificity in localizing primary tumors and metastases in patients with prostate cancer, but the individual overall survival probability is still difficult to estimate. Purpose To develop a prognostic risk score using PSMA PET-derived organ-specific total tumor volumes for predicting overall survival in patients with prostate cancer. Materials and Methods Men with prostate cancer who underwent PSMA PET/CT from January 2014 to December 2018 were evaluated retrospectively. All patients from center A were split into training (80%) and internal validation (20%) cohorts. Randomly selected patients from center B were used for external validation. Organ-specific tumor volumes were automatically quantified from PSMA PET scans by a neural network. A prognostic score was selected using multivariable Cox regression guided by the Akaike information criterion (AIC). The final prognostic risk score fitted on the training set was applied to both validation cohorts. Results A total of 1348 men (mean age, 70 years ± 8 [SD]) were included, with 918 patients in the training cohort, 230 in the internal validation cohort, and 200 in the external validation cohort. The median follow-up time was 55.7 months (IQR, 46.7-65.1 months; >4 years; 429 deaths occurred). A body weight-adjusted prognostic risk score integrating total, bone, and visceral tumor volumes obtained high C index values in the internal (0.82) and external (0.74) validation cohorts, as well as in patients with castration-resistant (0.75) and hormone-sensitive (0.68) disease. The fit of the statistical model for the prognostic score was improved compared with a model containing total tumor volume only (AIC, 3324 vs 3351; likelihood ratio test, P < .001). Calibration plots ascertained good model fit. Conclusion The newly developed risk score that included prostate-specific membrane antigen PET-derived organ-specific tumor volumes had good model fit for predicting overall survival in both internal and external validation cohorts. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Civelek in this issue.

Reversible epigenetic alterations mediate PSMA expression heterogeneity in advanced metastatic prostate cancer

Prostate-specific membrane antigen (PSMA) is an important cell surface target in prostate cancer. There are limited data on the heterogeneity of PSMA tissue expression in metastatic castration-resistant prostate cancer (mCRPC). Furthermore, the mechanisms regulating PSMA expression (encoded by the FOLH1 gene) are not well understood. Here, we demonstrate that PSMA expression is heterogeneous across different metastatic sites and molecular subtypes of mCRPC. In a rapid autopsy cohort in which multiple metastatic sites per patient were sampled, we found that 13 of 52 (25%) cases had no detectable PSMA and 23 of 52 (44%) cases showed heterogeneous PSMA expression across individual metastases, with 33 (63%) cases harboring at least 1 PSMA-negative site. PSMA-negative tumors displayed distinct transcriptional profiles with expression of druggable targets such as MUC1. Loss of PSMA was associated with epigenetic changes of the FOLH1 locus, including gain of CpG methylation and loss of histone 3 lysine 27 (H3K27) acetylation. Treatment with histone deacetylase (HDAC) inhibitors reversed this epigenetic repression and restored PSMA expression in vitro and in vivo. Collectively, these data provide insights into the expression patterns and regulation of PSMA in mCRPC and suggest that epigenetic therapies - in particular, HDAC inhibitors - can be used to augment PSMA levels.

Recent advances in the molecular targeted drugs for prostate cancer

CONTEXT

Prostate cancer (PCa) is the second largest male tumor in the world and one of the most common malignant tumors in the urinary system. In recent years, the incidence rate of PCa in China has been increasing year by year. Meanwhile, refractory hormone resistance and adverse drug reactions of advanced PCa cause serious harm to patients.

OBJECTIVE

The present study aims to systematically review the recent advances in molecularly targeted drugs for prostate cancer and to use the retrieval and analysis of the literature library to summarize the adverse effects of different drugs so as to maximize the treatment benefits of targeted therapies.

EVIDENCE ACQUISITION

We performed a systematic literature search of the Medline, EMBASE, PubMed, and Cochrane databases up to March 2022 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Medical Subject Heading (MeSH) terms and keywords such as (prostate cancer) AND (molecular target drugs) AND (side effect) were used. No language restrictions were set on the search process, and all these results were processed independently by two authors. Consensus was reached through discussion once met with any disagreements. The primary endpoint was differential features between different molecular targeted drugs. Secondary endpoints were side effects of different drugs on the body and corresponding prognostic values.

EVIDENCE SYNTHESIS

The Cochrane Collaboration risk of bias tool was used to assess the study quality in terms of sequence generation, allocation concealment, blinding, the completeness of outcome data, selective reporting and other biases. We retrieved 332 articles, of which 49 met the criteria for inclusion. Included studies show that prostatic tumor cells, tumor neovascularization and immune checkpoints are the main means for targeted therapy. Common drugs include 177 Lu-PSMA, Olaparib, Rucaparib, Bevacizumab, Pazopanib, Sorafenib, Cabozantinib, Aflibercept, Ipilimumab, Atezolizumab, Avelumab, Durvalumab. A series of publicly available data suitable for further analysis of side effects. An over-representation analysis of these datasets revealed reasonable dosage and usage is the key to controlling the side effects of targeted drugs. Important information such as the publication year, the first author, location and outcome observation of adverse effects was extracted from the original article. If the study data has some insufficient data, contacting the corresponding authors is necessary. All the studies included prospective nonrandomized and randomized research. Retrospective reviews were also screened according to the relevant to the purpose of this study. Meeting abstracts as well as letters to the editor and editorials were excluded.

STATISTICAL ANALYSIS

Data analysis was based on Cochrane's risk of bias tools to obtain the quality assessment. The included randomized studies used RoB2 and non-randomized ones corresponded to ROBINS-I. Standardized mean differences (SMD) were used to determine relative risk (RR) and side effects between groups. The eggers' test was used to check the publication bias from variable information in the included studies. All p < 0.05 were considered to be significant, and 95% was set as the confidence interval.

CONCLUSIONS

With the approval of a variety of targeted drugs, targeted therapy will be widely used in the treatment of advanced or metastatic prostate cancer. Despite the existence of adverse reactions related to targeted drug treatment, it is still meaningful to adjust the drug dosage or treatment cycle to reduce the occurrence of adverse reactions, improving the treatment benefits of patients.

Second Version of the Prostate Cancer Molecular Imaging Standardized Evaluation Framework Including Response Evaluation for Clinical Trials (PROMISE V2)

CONTEXT

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) is emerging to become a reference imaging tool for the staging and restaging of patients with prostate cancer for both clinical routine and trials. The prostate cancer molecular imaging standardized evaluation (PROMISE) criteria have been proposed as a framework for whole-body staging (molecular imaging TNM staging, denoted miTNM staging) to describe the prostate cancer disease extent on PSMA-PET.

OBJECTIVE

To create a comprehensive and integrated framework for PSMA-PET image interpretation and reporting.

EVIDENCE ACQUISITION

We propose the PROMISE V2 framework, which integrates an updated miTNM system, improved assessment of local disease, and a slightly modified PSMA-expression score for clinical routine. We have added a response monitoring framework defining qualitative and quantitative parameters to be recorded for a longitudinal assessment in clinical trials.

EVIDENCE SYNTHESIS

We provide a comprehensive literature review on the current use of the PROMISE framework in clinical research and prospective trials. PROMISE variables demonstrate a clear association with survival. PSMA expression assessed by the PSMA-expression score was used in several trials, and a low PSMA-expression score is a negative prognosticator of overall survival after ¹⁷⁷Lu-PSMA radioligand therapy. The proposed imaging parameters recorded for response assessment in clinical trials can be utilized to determine response according to PSMA-PET progression (PPP) or Response Evaluation Criteria in PSMA-PET/Computed Tomography (RECIP) frameworks, but also future response criteria.

CONCLUSIONS

PROMISE V2 offers standardized reporting of disease extent for clinical routine and research. Parameters recorded within clinical trials facilitate objective response assessment.

PATIENT SUMMARY

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) has become a standard imaging examination for prostate cancer. We propose a comprehensive framework for the analysis and reporting of PSMA-PET findings that will improve the communication between imaging experts and uro-oncologists.

Tumor Volume is a Better Prognostic Factor than Greatest Tumor Diameter in operated Stage I-III Non-small Cell Lung Cancer

INTRODUCTION

The aim of this study was to investigate the prognostic impact of tumor volume (TV, recorded from surgical specimens) on patients with stage I-III non-small-cell lung cancer (NSCLC) after complete resection.

MATERIALS AND METHODS

A total of 129 patients with stage I-III NSCLC diagnosed and underwent curative resection from 2007 to 2014 in our center were included in the study. Their clinico-pathological factors were retrospectively reviewed. Overall survival (OS) and disease-free survival (DFS) analyses were performed with the Kaplan-Meier method and Cox's hazard model. According to the ROC analysis, patients were divided into 2 groups (Group 1: 58 patients <30.3 cm³ and Group 2: 71 patients ≥30.3 cm³) and the OS and DFS values were compared.

RESULTS

Median TVs and greatest tumor diameter were 12 cm³ (0.1-30) / 3 cm (0.4-6.5) in Group 1 and 98 cm³ (30.6-1521) / 6 cm (3.5-21) in Group 2. Median OS was 53 (5-177) months in Group 1 and 38 (2-200) months in Group 2 (P < .001). DFS was similar in both group (28 [1-140] vs. 24 [1-155] months, Introduction P = .489). Kaplan-Meier curves showed significantly higher OS rates in Group 1 than Group 2 (P = .04). In multivariable analysis (TV, tumor T stage, tumor N stage, receiving adjuvant radiotherapy) showed that TV (HR: 0.293, 95% CI: 0.121-0.707, P = .006) and tumor N stage (HR: 0.013, 95% CI: 0.001-0.191, P = .02) were independent factors associated with OS.

CONCLUSION

Tumor volume, not considered in the routine TNM classification, may improve prediction accuracy of overall OS in operated Stage I-III NSCLC.

Reprint of: morphologic spectrum of treatment-related changes in prostate tissue and prostate cancer: an updated review

A wide range of treatment options are available to patients with prostate cancer. Some treatments are standard (currently used) while some are emerging therapies. Androgen deprivation therapy is typically reserved for localized or metastatic prostate cancer not amenable to surgery. Radiation therapy may be offered to individuals for local therapy with curative intent in low- or intermediate-risk disease that may have a high probability of progression on active surveillance or where surgery is not suitable. Focal therapy/ablation treatment is an alternative approach for those who prefer to avoid radical prostatectomy for localized disease of low- or intermediate-risk or as salvage therapy after failed radiation therapy. Chemotherapy and immunotherapy remain under investigation and are currently used for androgen-independent disease or hormone-refractory prostate cancer; however, a better understanding of therapeutic efficacy is needed. Histopathologic changes observed in benign and malignant prostate tissue induced by hormonal therapies and radiation therapy are well described, whereas treatment-related effects secondary to novel therapies continue to be documented although their clinical significance is not absolutely clear. An informed and accurate evaluation of post-treatment prostate specimens requires pathologists with diagnostic acumen and knowledge relating to the histopathologic spectrum associated with each treatment option. In situations when clinical history is lacking, but morphologic features are suggestive of prior treatment, pathologists are encouraged to consult clinical colleagues regarding prior treatment history including details of when treatment was initiated and duration of therapy. This review aims to provide a concise update of current and emerging therapies for prostate cancer, histologic alterations and recommendations on Gleason grading.

Advanced PSMA-PET/CT Imaging Parameters in Newly Diagnosed Prostate Cancer Patients for Predicting Metastatic Disease

(1) Purpose: Recent studies indicate that advanced imaging parameters such as prostate PSMA tumor volume may have a value in predicting response to treatment of castration-resistant prostate cancer patients. In this study, we examine whether a relationship can be found between advanced imaging parameters such as prostate PSMA-TV and the presence of metastatic disease in newly diagnosed prostate cancer patients undergoing PSMA-PET/CT for staging purposes; (2) Methods: We retrospectively analyzed PET/CT studies of 91 patients with newly diagnosed prostate cancer. Prostate PSMA-TV was measured using the MIRADA-XD software. PET/CT results were recorded, as well as additional clinical parameters such as the Gleason score, etc.; (3) Results: Prostate PSMA-TV measurements were found to be able to significantly differentiate metastatic from the non-metastatic patient groups (13.7 vs. 5.5, p-value < 0.05). Overall, 54% percent of patients with levels of over 8.1 PSMA-TV had metastatic lesions found on their PSMA-PET/CT. A model based on this cutoff attained a sensitivity of 80%, a specificity of 68.3%, and a negative predictive value of 93.5% for identifying metastatic disease. Another bin model was found statistically capable of assessing the likelihood of the presence of metastatic disease with a p-value of 0.001; (4) Conclusions: Prostate PSMA-TV measurement has the potential to predict the presence of metastatic disease at staging and thus may impact further treatment decision and patient management.

Single Center Experience with a 4-Week 177Lu-PSMA-617 Treatment Interval in Patients with Metastatic Castration-Resistant Prostate Cancer

Background: 177Lu-PSMA-617 is a promising theragnostic treatment for metastatic castration-resistant prostate cancer (mCRPC). However, both the optimal treatment dose and interval in mCRPC and the rate of identification of responders from non-responders among possible treatment candidates are unknown. Methods: 62 men with mCRPC who were treated with 177Lu-PSMA-617 during 1/2017−2/2019 were included in the study. Treatment responses, overall survival (OS) and progression free survival (PFS) were determined. The median follow-up time was 1.4 years (IQR 0.5−2.2). Tumor volume of metastases (MTV), SUVmax and tumor lesion activity (TLA) were quantitated from pre-treatment PSMA PET/CT images together with pre-treatment PSA. Results: An average of three treatment cycles (2−5) were given within a four-week interval. PFS was 4.9 months (2.4−9.6) and OS was 17.2 months (6−26.4). There were no major adverse events reported. A significant PSA response of >50% was found in 58.7% of patients, which was significantly associated with longer OS, p < 0.004. PSA response was not associated with staging PSMA-derived parameters. Conclusions: 177Lu-PSMA-617 treatment in four-week intervals was safe and effective. Almost 60% of patients had a significant PSA response, which was associated with better OS. Pre-treatment PSA kinetics or staging PSMA PET/CT-derived parameters were not helpful in identifying treatment responders from non-responders; better biomarkers are needed to aid in patient selection.

Lutetium Lu 177 vipivotide tetraxetan for metastatic castration-resistant prostate cancer

INTRODUCTION

¹⁷⁷Lu-vipivotide tetraxetan is a radiopharmaceutical that selectively targets prostate-specific membrane antigen (PSMA) and delivers beta-radiations to kill prostate cancer cells.

AREAS COVERED

Extensive experience outside the United States as well as randomized phase II and phase III data demonstrate that ¹⁷⁷Lu-vipivotide tetraxetan is a safe, generally well tolerated, and effective therapy for men with mCRPC. ¹⁷⁷Lu-vipivotide tetraxetan was approved by the FDA in March 2022 for the treatment of PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) after androgen receptor pathway inhibition and taxane-based chemotherapy based on the results of the VISION trial.

EXPERT OPINION

This review discusses the development and studies leading to the approval of ¹⁷⁷Lu-vipivotide tetraxetan. In all, ¹⁷⁷Lu-vipivotide tetraxetan is an exciting new tool in the arsenal for men with mCRPC after novel androgen pathway inhibitors and at least one taxane chemotherapy. Optimal selection of patients, sequencing of ¹⁷⁷Lu-vipivotide tetraxetan with the other agents available to treat mCRPC, and the use of dosimetry are current areas of interest with great potential and opportunities for further individual patient optimization using the tools of theranostics.

Role of baseline 68Ga-PSMA PET/CT-derived whole-body volumetric parameters in predicting survival outcomes of metastatic castration-resistant prostate cancer patients receiving first-line treatment

OBJECTIVE

We aimed to evaluate whether baseline ⁶⁸Ga-PSMA PET/CT-derived whole-body volumetric parameters could be used as predictive biomarkers for survival in metastatic castration-resistant prostate cancer (mCRPC) patients receiving first-line treatment.

MATERIALS AND METHODS

This retrospective study included 54 mCRPC patients, who underwent baseline ⁶⁸Ga-PSMA PET/CT imaging within 1 month before starting first-line treatment. Pre-treatment prostate-specific antigen (PSA) levels and treatments were recorded. SUVmax, SUVmean, whole-body PSMA-derived tumor volume (wbPSMA-TV), and whole-body total lesion PSMA (wbTL-PSMA) were calculated for all patients. PSA response was defined as a decline of ≥ 50% from pre-treatment value at 12 weeks. Overall survival (OS) was measured from the start of the first-line treatment for mCRPC.

RESULTS

Docetaxel and abiraterone/enzalutamide were administered to 32 and 22 patients in the first-line setting, respectively. wbPSMA-TV (rho = 0.582, p = 0.004) and wbTL-PSMA (rho = 0.564, p = 0.007) showed moderate positive correlations with PSA levels. Older age (p = 0.02), higher wbPSMA-TV (p = 0.007), higher PSA (p = 0.01), higher number of bone metastases (p = 0.02), and lack of PSA response (p = 0.03) were significantly associated with an increased risk of mortality. Multivariate analysis determined wbPSMA-TV (HR: 1.003, 95% CI 1.001-1.004, p = 0.001) and PSA response (HR: 2.241, 95% CI 1.189-4.222, p = 0.01) as independent predictors of OS.

CONCLUSION

The wbPSMA-TV may be a useful tool to reflect tumor burden and predict survival outcomes in patients with mCRPC.

Current status and progress in using radiolabelled PARP-1 inhibitors for imaging PARP-1 expression in tumours

Poly(ADP-ribose) polymerase-1 (PARP-1) is a key enzyme in the DNA repair process, and the overexpression of PARP-1 in several tumours makes this enzyme a promising molecular target. Recently, several PARP-1 inhibitors, such as olaparib, rucaparib, niraparib and talazoparib, have been clinically approved as anticancer drugs. Several of these inhibitors have been radiolabelled for noninvasive imaging of PARP-1 expression in several types of tumours. In this review, the background and progress for using various radiolabelled PARP-1 inhibitors for cancer diagnosis are discussed and future development directions are proposed.

Fully automatic prognostic biomarker extraction from metastatic prostate lesion segmentations in whole-body [68Ga]Ga-PSMA-11 PET/CT images

PURPOSE

This study aimed to develop and assess an automated segmentation framework based on deep learning for metastatic prostate cancer (mPCa) lesions in whole-body [⁶⁸Ga]Ga-PSMA-11 PET/CT images for the purpose of extracting patient-level prognostic biomarkers.

METHODS

Three hundred thirty-seven [⁶⁸Ga]Ga-PSMA-11 PET/CT images were retrieved from a cohort of biochemically recurrent PCa patients. A fully 3D convolutional neural network (CNN) is proposed which is based on the self-configuring nnU-Net framework, and was trained on a subset of these scans, with an independent test set reserved for model evaluation. Voxel-level segmentation results were assessed using the dice similarity coefficient (DSC), positive predictive value (PPV), and sensitivity. Sensitivity and PPV were calculated to assess lesion level detection; patient-level classification results were assessed by the accuracy, PPV, and sensitivity. Whole-body biomarkers total lesional volume (TLV_auto) and total lesional uptake (TLU_auto) were calculated from the automated segmentations, and Kaplan-Meier analysis was used to assess biomarker relationship with patient overall survival.

RESULTS

At the patient level, the accuracy, sensitivity, and PPV were all > 90%, with the best metric being the PPV (97.2%). PPV and sensitivity at the lesion level were 88.2% and 73.0%, respectively. DSC and PPV measured at the voxel level performed within measured inter-observer variability (DSC, median = 50.7% vs. second observer = 32%, p = 0.012; PPV, median = 64.9% vs. second observer = 25.7%, p < 0.005). Kaplan-Meier analysis of TLV_auto and TLU_auto showed they were significantly associated with patient overall survival (both p < 0.005).

CONCLUSION

The fully automated assessment of whole-body [⁶⁸Ga]Ga-PSMA-11 PET/CT images using deep learning shows significant promise, yielding accurate scan classification, voxel-level segmentations within inter-observer variability, and potentially clinically useful prognostic biomarkers associated with patient overall survival.

TRIAL REGISTRATION

This study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12615000608561) on 11 June 2015.

Outcome of 177 Lu-PSMA Radionuclide Treatment in Advanced Prostate Cancer and Its Association With Clinical Parameters : A Single-Center Experience

PURPOSE

This study was set out to analyze the efficacy and safety of 177 Lu-PSMA-617 (LuPSMA) treatment in metastatic castration-resistant prostate cancer (mCRPC) patients.

PATIENTS AND METHODS

Progressive mCRPC patients who received at least 1 cycle of LuPSMA therapy were evaluated retrospectively. Demographic, clinic, and histopathological data were documented. Treatment efficacy was determined based on biochemical response criteria (Prostate Cancer Clinical Trial Working Group 3), and toxicity rates were defined based on CTCAE v4.03. The prognostic significance of laboratory/clinical data and 68 Ga-PSMA PET/CT quantitative results were analyzed using SPSS Version 24.0.

RESULTS

One hundred patients (median prostate-specific antigen [PSA] level, 75.7 ng/mL) who met the eligibility criteria were identified. The median number of cycles received per patient was 3 (range, 1-9). After the first cycles of LuPSMA, biochemical partial response, biochemical stable disease, and biochemical progressive disease were observed in 31%, 36%, and 33% of patients, respectively. Any PSA decline was determined in 60% of patients. After the fourth cycle of treatment, biochemical partial response, biochemical stable disease, and biochemical progressive disease were defined in 48%, 26%, and 26% of patients, respectively. The median overall survival (OS) from the first cycle of LuPSMA was 14 months. Patients who had any PSA response after the first cycle had significantly longer OS than nonresponders (median OS: 17 vs 9 months; P ≤ 0.001). Total PSMA-derived tumor volume ( P = 0.004), total PSMA activity per lesion ( P = 0.01), PSA ( P = 0.007), alkaline phosphatase ( P = 0.002), lactate dehydrogenase ( P < 0.001), and hemoglobin ( P < 0.001) were significant prognostic factors for OS in univariate Cox regression analysis.

CONCLUSIONS

LuPSMA therapy is a favorable treatment for mCRPC with remarkable therapeutic efficacy and low toxicity rates, even in progressive disease under standard therapies. Baseline PSMA-based tumor burden, PSA, alkaline phosphatase, lactate dehydrogenase, and hemoglobin were significant predictors of OS and can be useful for selection of the best candidate for LuPSMA therapy.

Morphologic spectrum of treatment-related changes in prostate tissue and prostate cancer: An Updated Review

A wide range of treatment options is available to patients with prostate cancer. Some treatments are standard (currently used) while some are emerging therapies. Androgen deprivation therapy is typically reserved for localized or metastatic prostate cancer not amenable to surgery. Radiation therapy may be offered to individuals for local therapy with curative intent in low- or intermediate-risk disease that may have a high probability of progression on active surveillance or where surgery is not suitable. Focal therapy/ablation treatment is an alternative approach for those who prefer to avoid radical prostatectomy for localized disease of low- or intermediate-risk or as salvage therapy following failed radiation therapy. Chemotherapy and immunotherapy remain under investigation and are currently used for androgen-independent disease or hormone-refractory prostate cancer; however a better understand therapeutic efficacy is needed. Histopathologic changes observed in benign and malignant prostate tissue induced by hormonal therapies and radiation therapy is well described, while treatment-related effects secondary to novel therapies continue to be documented although their clinical significance is not absolutely clear. An informed and accurate evaluation of post-treatment prostate specimens requires pathologists with diagnostic acumen and knowledge relating to the histopathologic spectrum associated with each treatment option. In situations when clinical history is lacking, but morphologic features are suggestive of prior treatment, pathologists are encouraged to consult clinical colleagues regarding prior treatment history including details of when treatment was initiated and duration of therapy. This review aims to provide a concise update of current and emerging therapies for prostate cancer, histologic alterations and recommendations on Gleason grading.

Utility of PET to Appropriately Select Patients for PSMA-Targeted Theranostics

ABSTRACT

The majority of aggressive prostate cancers overexpress the transmembrane protein prostate-specific membrane antigen (PSMA). PSMA is, therefore, an attractive target for drug development. Over the last decade, numerous PSMA-targeted radiopharmaceuticals for imaging and therapy have been developed and investigated in theranostic combination. PSMA-targeted radiopharmaceuticals for imaging have been primarily developed for PET. PSMA PET provides whole-body evaluation of the degree of PSMA expression on tumors and potentially provides a method to better select patients for PSMA-targeted therapy. Numerous PSMA-targeted therapeutic agents using β- or α-particle emitters are under study in clinical trials. In particular, the β-particle-emitting radioisotope 177Lu bound to PSMA-targeted small molecules have ongoing and completed late-stage clinical trials in metastatic castration-resistant prostate cancer. To define the most appropriate patient group for PSMA-targeted therapeutics, multiple studies have investigated PSMA and FDG PET/CT to establish PET parameters as predictive and prognostic biomarkers. This article discusses recent clinical trials that examine the optimal use of PET for the selection of patients for PSMA-targeted therapeutics and provides an integrative overview of choice of PET tracer(s), targeting molecule, therapeutic radioisotope, nonradioactive therapy, and cancer type (prostate or nonprostate).

Diffuse Bone Marrow Involvement of Multiple Myeloma on [18F]PSMA-1007 PET/CT: Is There a Theranostic Potential?

ABSTRACT

A 71-year-old man presented with chronic anemia (hemoglobin 7.3 g/dL). Further serum analyses showed elevated prostate-specific antigen (13 ng/mL), suggestive of prostate cancer. However, ultrasound-guided transrectal sextant biopsy did not find any evidence of prostate cancer. In order to improve guidance of intended repeated biopsy, [18F]prostate-specific membrane antigen (PSMA) 1007 PET/CT was performed, which showed a solitary lesion with strong PSMA expression in the left peripheral zone in the prostate gland. Surprisingly, also a diffuse bone marrow involvement with predominantly osteolytic lesions was observed. This massive osseous tumor burden was clearly discordant to the only relatively mild elevated prostate-specific antigen. The subsequent bone biopsy revealed multiple myeloma. This case does not only highlight a possible pitfall on PSMA PET/CT, but also raises the question on how far PSMA ligands may offer diagnostic and therapeutic potential in multiple myeloma.

Freely available artificial intelligence for pelvic lymph node metastases in PSMA PET-CT that performs on par with nuclear medicine physicians

PURPOSE

The aim of this study was to develop and validate an artificial intelligence (AI)-based method using convolutional neural networks (CNNs) for the detection of pelvic lymph node metastases in scans obtained using [¹⁸F]PSMA-1007 positron emission tomography-computed tomography (PET-CT) from patients with high-risk prostate cancer. The second goal was to make the AI-based method available to other researchers.

METHODS

[¹⁸F]PSMA PET-CT scans were collected from 211 patients. Suspected pelvic lymph node metastases were marked by three independent readers. A CNN was developed and trained on a training and validation group of 161 of the patients. The performance of the AI method and the inter-observer agreement between the three readers were assessed in a separate test group of 50 patients.

RESULTS

The sensitivity of the AI method for detecting pelvic lymph node metastases was 82%, and the corresponding sensitivity for the human readers was 77% on average. The average number of false positives was 1.8 per patient. A total of 5-17 false negative lesions in the whole cohort were found, depending on which reader was used as a reference. The method is available for researchers at www.recomia.org .

CONCLUSION

This study shows that AI can obtain a sensitivity on par with that of physicians with a reasonable number of false positives. The difficulty in achieving high inter-observer sensitivity emphasizes the need for automated methods. On the road to qualifying AI tools for clinical use, independent validation is critical and allows performance to be assessed in studies from different hospitals. Therefore, we have made our AI tool freely available to other researchers.

Total Tumor Volume on 18F-PSMA-1007 PET as Additional Imaging Biomarker in mCRPC Patients Undergoing PSMA-Targeted Alpha Therapy with 225Ac-PSMA-I&T

Background: PSMA-based alpha therapy using 225Ac-PSMA-I&T provides treatment for metastatic castration-resistant prostate cancer (mCRPC), even after the failure of 177Lu-PSMA radioligand therapy (RLT). In clinical routine, the total tumor volume (TTV) on PSMA PET impacts therapy outcomes and plays an increasing role in mCRPC patients. Hence, we aimed to assess TTV and its changes during 225Ac-PSMA-I&T RLT. Methods: mCRPC patients undergoing RLT with 225Ac-PSMA-I&T with available 18F-PSMA-1007 PET/CT prior to therapy initiation were included. TTV was assessed in all patients using established cut-off values. Image derived, clinical and biochemistry parameters (PSA, LDH, AP, pain score) were analyzed prior to and after two cycles of 225Ac-PSMA. Changes in TTV and further parameters were directly compared and then correlated with established response criteria, such as RECIST 1.1 or mPERCIST. Results: 13 mCRPC patients were included. The median overall survival (OS) was 10 months. Prior to 225Ac-PSMA RLT, there was no significant correlation between TTV with other clinical parameters (p > 0.05 each). Between short-term survivors (STS, <10 months OS) and long-term survivors (LTS, ≥10 months OS), TTV and PSA were comparable (p = 0.592 & p = 0.286, respectively), whereas AP was significantly lower in the LTS (p = 0.029). A total of 7/13 patients completed two cycles and underwent a follow-up 18F-PSMA-1007 PET/CT. Among these patients, there was a significant decrease in TTV (median 835 vs. 201 mL, p = 0.028) and PSA (median 687 ng/dL vs. 178 ng/dL, p = 0.018) after two cycles of 225Ac-PSMA RLT. Here, percentage changes of TTV after two cycles showed no direct correlation to all other clinical parameters (p > 0.05 each). In two patients, new PET-avid lesions were detected on 18F-PSMA-1007 PET/CT. However, TTV and PSA were decreasing or stable. Conclusion: PET-derived assessment of TTV is an easily applicable imaging biomarker independent of other established parameters prior to 225Ac-PSMA RLT in these preliminary follow-up data. Even after the failure of 177Lu-PSMA, patients with extensive TTV seem to profit from RLT. All but one patient who was eligible for ≥2 cycles of 225Ac-PSMA-RLT demonstrated drastic TTV decreases without direct correlation to other biomarkers, such as serum PSA changes. Changes in TTV might hence improve the response assessment compared to standard classifiers by reflecting the current tumor load independent of the occurrence of new lesions.

Predictors and Real-World Use of Prostate-Specific Radioligand Therapy: PSMA and Beyond

PSMA is a transmembrane protein that is markedly overexpressed in prostate cancer, making it an excellent target for imaging and treating patients with prostate cancer. Several small molecule inhibitors and antibodies of PSMA have been radiolabeled for use as therapeutic agents and are currently under clinical investigation. PSMA-based radionuclide therapy is a promising therapeutic option for men with metastatic prostate cancer. The phase II TheraP study demonstrated superior efficacy, lower side effects, and improved patient-reported outcomes compared with cabazitaxel. The phase III VISION study demonstrated that radionuclide therapy with β-emitter ¹⁷⁷Lu-PSMA-617 can prolong survival and improve quality of life when offered in addition to standard-of-care therapy in men with PSMA-positive metastatic castration-resistant prostate cancer whose disease had progressed with conventional treatments. Nevertheless, up to 30% of patients have inherent resistance to PSMA-based radionuclide therapy, and acquired resistance is inevitable. Hence, strategies to increase the efficacy of PSMA-based radionuclide therapy have been under clinical investigation. These include better patient selection; increased radiation damage delivery via dosimetry-based administered dose or use of α-emitters instead of β-emitters; or using combinatorial approaches to overcome radioresistance mechanisms (innate or acquired), such as with novel hormonal agents, PARP inhibitors, or immunotherapy.

Biomarkers to personalize treatment with 177Lu-PSMA-617 in men with metastatic castration-resistant prostate cancer - a state of the art review

Radioligand therapy with Lutetium-177 (177Lu)-Prostate-specific membrane antigen (PSMA) has shown to prolong survival in metastatic castration resistant prostate cancer (mCRPC). One of the major challenges for clinicians in the future is to select those patients who would benefit most from this therapy to position it in the treatment landscape of mCRPC. This, in turn, will lead to the delivery of personalized therapies. In this narrative review article we summarize recent studies investigating both predictive and prognostic clinical, imaging-based, and molecular biomarkers to predict treatment response to 177Lu-PSMA-617 radioligand therapy with the aim of identifying men who should be considered for this approach. Of note, the evidence on the role of biomarkers currently relies on small retrospective trials and their validation in larger prospective cohorts is necessary before these results can be translated in the clinical practice.

Targeting PSMA Revolutionizes the Role of Nuclear Medicine in Diagnosis and Treatment of Prostate Cancer

Simple Summary

Imaging plays a crucial role in the accurate staging of prostate cancer. Prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer cells, and targeting the PSMA protein for diagnostic purposes has become of great clinical value. Another valuable feature of PSMA is its opportunity to serve as a target for delivering radionuclide therapy to cancer cells. PSMA-ligands can be labeled with various radionuclides, such as alpha and beta-emitters. This review offers an overview of the literature on recent developments in nuclear medicine regarding PSMA in prostate cancer diagnostics and targeted radionuclide therapy.

Abstract

Targeting the prostate-specific membrane antigen (PSMA) protein has become of great clinical value in prostate cancer (PCa) care. PSMA positron emission tomography/computed tomography (PET/CT) is increasingly used in initial staging and restaging at biochemical recurrence in patients with PCa, where it has shown superior detection rates compared to previous imaging modalities. Apart from targeting PSMA for diagnostic purposes, there is a growing interest in developing ligands to target the PSMA-protein for radioligand therapy (RLT). PSMA-based RLT is a novel treatment that couples a PSMA-antibody to (alpha or beta-emitting) radionuclide, such as Lutetium-177 (¹⁷⁷Lu), to deliver high radiation doses to tumor cells locally. Treatment with ¹⁷⁷Lu-PSMA RLT has demonstrated a superior overall survival rate within randomized clinical trials as compared to routine clinical care in patients with metastatic castration-resistant prostate cancer (mCRPC). The current review provides an overview of the literature regarding recent developments in nuclear medicine related to PSMA-targeted PET imaging and Theranostics.