South African guidelines for receptor radioligand therapy (RLT) with Lu-177-PSMA in prostate cancer

Six country vignettes: Strengthening radiotherapy and theranostics

BACKGROUND

For cancer patient populations worldwide, the synchronous scale-up of diagnostics and treatments yields meaningful gains in survival and quality of life. Among advanced cancer therapies, radiotherapy (RT) and theranostics are key to achieving practical, high-quality, and personalized precision medicine - targeting disease manifestations of individual patients and broad populations, alike. Aiming to learn from one another across different world regions, the six country vignettes presented here depict both challenges and victories in de novo establishment or improvement of RT and theranostics infrastructure.

METHODS

The International Atomic Energy Agency (IAEA) convened global RT and theranostics experts from diverse world regions and contexts to identify relevant challenges and report progress in their own six countries: Belgium, Brazil, Costa Rica, Jordan, Mongolia, and South Africa. These accounts are collated, compared, and contrasted herein.

RESULTS

Common challenges persist which could be more strategically assessed and addressed. A quantifiable discrepancy entails personnel. The estimated radiation oncologists (ROs), nuclear medicine physicians (NMPs), and medical physicists (MPs for RT and nuclear medicine) per million inhabitants in the six collective countries respectively range between 2.69-38.00 ROs, 1.00-26.00 NMPs, and 0.30-3.45 MPs (Table 1), reflecting country-to-country inequities which largely match World Bank country-income stratifications.

CONCLUSION

Established goals for RT and nuclear medicine advancement worldwide have proven elusive. The pace of progress could be hastened by enhanced approaches such as more sustainably phased implementation; better multinational networking to share lessons learned; routine quality and safety audits; as well as capacity building employing innovative, resource-sparing, cutting-edge technologic approaches. Bodies such as ministries of health, professional societies, and the IAEA shall serve critical roles in convening and coordinating more innovative RT and theranostics translational research, including expanding nuanced global database metrics to inform, reach, and potentiate milestones most meaningfully.

POLICY SUMMARY

Aligned with WHO 25×25 NCDs target; WHA70.12 and WHA76.5 resolutions.

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.

Radiolabeled PSMA Inhibitors

PSMA has shown to be a promising target for diagnosis and therapy (theranostics) of prostate cancer. We have reviewed developments in the field of radio- and fluorescence-guided surgery and targeted photodynamic therapy as well as multitargeting PSMA inhibitors also addressing albumin, GRPr and integrin αvβ3. An overview of the regulatory status of PSMA-targeting radiopharmaceuticals in the USA and Europe is also provided. Technical and quality aspects of PSMA-targeting radiopharmaceuticals are described and new emerging radiolabeling strategies are discussed. Furthermore, insights are given into the production, application and potential of alternatives beyond the commonly used radionuclides for radiolabeling PSMA inhibitors. An additional refinement of radiopharmaceuticals is required in order to further improve dose-limiting factors, such as nephrotoxicity and salivary gland uptake during endoradiotherapy. The improvement of patient treatment achieved by the advantageous combination of radionuclide therapy with alternative therapies is also a special focus of this review.

Global experience with PSMA-based alpha therapy in prostate cancer

Purpose

This review discusses the current state of prostate-specific membrane antigen (PSMA)-based alpha therapy of metastatic castration-resistant prostate cancer (mCRPC). With this in-depth discussion on the growing field of PSMA-based alpha therapy (PAT), we aimed to increase the interactions between basic scientists and physician–scientists in order to advance the field.

Methods

To achieve this, we discuss the potential, current status, and opportunities for alpha therapy and strategies, attempted to date, and important questions that need to be addressed. The paper reviews important concepts, including whom to treat, how to treat, what to expect regarding treatment outcome, and toxicity, and areas requiring further investigations.

Results

There is much excitement about the potential of this field. Much of the potential exists because these therapies utilize unique mechanisms of action, difficult to achieve with other conventional therapies.

Conclusion

A better understanding of the strengths and limitations of PAT may help in creating an effective therapy for mCRPC and design a rational combinatorial approach to treatment by targeting different tumor pathways.

Prior therapies as prognostic factors of overall survival in metastatic castration-resistant prostate cancer patients treated with [177Lu]Lu-PSMA-617. A WARMTH multicenter study (the 617 trial)

Introduction

The impact of prior therapies, especially chemotherapy, on overall survival (OS) in patients with castration-resistant prostate cancer (CRPC) receiving [¹⁷⁷Lu]Lu-PSMA-617 therapy has been the subject of controversy. Therefore, WARMTH decided to plan a multicenter retrospective analysis (the “617 trial”) to evaluate response rate and OS as well as the impact of prior therapies on OS in more than 300 patients treated with ¹⁷⁷Lu-PSMA-617.

Materials and methods

The data of 631 metastatic CRPC (mCRPC) patients from 11 different clinics were evaluated. According to the inclusion and exclusion criteria, all patients had to have received at least abiraterone or enzalutamide prior to [¹⁷⁷Lu]Lu-PSMA-617 therapy. The patients were divided into three groups: patients who had received prior chemotherapy, patients who avoided chemotherapy, and patients for whom a chemotherapy was contraindicated.

Results

The analysis included the data of 416 patients, with a median age of 71.9 years. At the time of analysis, 87 patients (20,9%) were still alive. A total of 53.6% of patients had received both abiraterone and enzalutamide; 75.5% and 26.4% had a history of chemotherapy with docetaxel and cabazitaxel, respectively. A total of 20.4% had had Ra-223. The median OS was 11.1 months. Prior chemotherapy, the existence of bone and liver metastases, as well as Eastern Cooperative Oncology Group (ECOG) status, were significant prognosticators of worse overall survival in both univariate and multivariate analyses. Patients without any prior chemotherapy showed a significantly longer OS (14.6 months). The median OS in patients who received one or two lines of chemotherapy with docetaxel or docetaxel followed by cabazitaxel, respectively, was 10.9 months and 8.9 months. There was no difference in OS between patients who had not received chemotherapy and patients for whom chemotherapy was contraindicated. The other prior therapies did not have any significant impact on OS.

Conclusion

In the present multicenter analysis, chemotherapy-naïve mCRPC patients receiving [¹⁷⁷Lu]Lu-PSMA-617 therapy had a significantly longer OS than patients with a history of chemotherapy. This remained independent in the multivariate analysis besides presence of bone and liver metastases as negative prognosticators for survival, whereas an ECOG of 0–1 is associated with a longer OS.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-04797-9) contains supplementary material, which is available to authorized users.