By Gilang Cahya 
A groundbreaking study originating from the UCLA Health Jonsson Comprehensive Cancer Center has unveiled a startling reality: a significant proportion of men diagnosed with high-risk, nonmetastatic hormone-sensitive prostate cancer may, in fact, harbor more advanced disease than previously understood. This revelation, stemming from the application of cutting-edge imaging technology, carries profound implications for patient diagnosis, treatment strategies, and the very foundation of clinical trial design in prostate cancer research.
The Limitations of Conventional Imaging
For decades, the staging of prostate cancer has relied heavily on conventional imaging techniques, such as computed tomography (CT) scans and bone scintigraphy. While these methods have served as crucial tools in identifying the extent of disease spread, the new UCLA study, published in the esteemed journal JAMA Network Open, suggests they possess inherent limitations, particularly in accurately assessing the presence of microscopic or early-stage metastases in high-risk patients.
The research team, led by Dr. Jeremie Calais, Director of the Ahmanson Translational Theranostics Division’s clinical research program and associate professor at the David Geffen School of Medicine at UCLA, retrospectively analyzed data from 182 patients. These individuals had high-risk recurrent prostate cancer and were initially considered to have disease confined to the prostate gland, making them eligible for the influential EMBARK clinical trial. The EMBARK trial, a landmark study in prostate cancer treatment, demonstrated that the addition of enzalutamide, a potent hormone therapy, to standard androgen deprivation therapy (ADT) significantly improved metastasis-free survival for men with high-risk nonmetastatic prostate cancer.
However, the classification of patients within the EMBARK trial was based on the diagnostic capabilities of conventional imaging modalities. The UCLA researchers hypothesized that these methods might have underestimated the true extent of metastatic disease in a subset of these patients.
PSMA-PET: A New Era in Prostate Cancer Imaging
The cornerstone of the UCLA study’s findings lies in the application of prostate-specific membrane antigen-positron emission tomography (PSMA-PET) imaging. This advanced technology represents a significant leap forward in visualizing prostate cancer. PSMA is a protein that is highly expressed on prostate cancer cells, even when they have spread to other parts of the body. PSMA-PET imaging utilizes radiotracers – small amounts of radioactive substances – that are designed to bind specifically to PSMA. When these radiotracers accumulate in cancer cells, they emit signals that can be detected by a PET scanner, creating detailed images that highlight the precise location and extent of cancerous tissue.
Unlike conventional imaging, which primarily provides anatomical information (i.e., the size and shape of organs and potential tumors), PSMA-PET offers functional imaging. This means it can reveal the biological activity of cancer cells, offering a more nuanced and sensitive picture of disease presence and spread. This functional insight is critical, as it can detect cancer cells that may be too small or too diffuse to be identified by traditional anatomical imaging.
Startling Findings: A Significant Underestimation
The results of the UCLA study were striking. When the 182 patients, who had been previously classified as having nonmetastatic disease, were re-evaluated using PSMA-PET imaging, a substantial number were found to have metastatic disease. Specifically, PSMA-PET detected cancer metastases in an astonishing 46% of these patients.
"Our study demonstrates the critical role of PSMA-PET in accurately staging prostate cancer, which can significantly impact treatment decisions and outcomes," stated Dr. Jeremie Calais, the senior author of the study. "We anticipated that PSMA-PET would detect more suspicious findings compared to conventional imaging. However, it was informative to uncover such a high number of metastatic findings in a well-defined cohort of patients resembling the EMBARK trial population that was supposed to only include those without metastases," added Dr. Adrien Holzgreve, a visiting assistant professor at the David Geffen School of Medicine and the study’s first author.
The findings were even more pronounced when examining the number of lesions. The study revealed that 24% of the patients exhibited five or more metastatic lesions that had been entirely missed by conventional imaging. This suggests that for a considerable portion of men deemed to have localized disease, the cancer had already disseminated, albeit at a level undetectable by standard diagnostic tools.
Implications for Treatment and Clinical Trials
The implications of these findings are far-reaching and touch upon several critical aspects of prostate cancer management.
Redefining Patient Eligibility for Clinical Trials
One of the most immediate consequences is the potential reevaluation of patient selection criteria for clinical trials. Trials like EMBARK, which have been instrumental in advancing treatment protocols, relied on conventional imaging for patient stratification. If nearly half of the patients in such a trial were, in fact, metastatic according to PSMA-PET, it raises questions about how these past trial results should be interpreted and whether the efficacy of treatments might be different in a more accurately staged population.
"These results challenge the interpretation of previous studies, like the EMBARK trial, and support the inclusion of PSMA-PET for patient selection in clinical and trial interventions in prostate cancer in future major industry-sponsored clinical trials," the researchers concluded. This call for integrating PSMA-PET into future trial designs aims to ensure that studies are conducted with a more precise understanding of disease burden, leading to more robust and reliable findings.
Impact on Treatment Decisions
Accurate staging is paramount for determining the most effective treatment strategy. For patients with nonmetastatic disease, treatment options typically focus on local therapies such as surgery or radiation therapy, with the goal of eradicating the cancer within the prostate. However, for patients with metastatic disease, systemic therapies, including hormone therapy, chemotherapy, and potentially targeted radiotherapies, become necessary to manage the cancer throughout the body.
The discovery that a significant percentage of men with "nonmetastatic" disease actually have metastases means that some patients may have been undertreated. This could have led to a delay in initiating more aggressive or systemic therapies, potentially allowing the cancer to progress further. Conversely, some patients may have received treatments for localized disease that were not optimally suited for their actual disease stage.
The findings open the door to potentially curative options for some patients. For instance, targeted radiotherapy, which uses radioactive agents that specifically target cancer cells expressing PSMA, is a promising treatment for metastatic prostate cancer. If PSMA-PET can accurately identify metastatic lesions, it can guide the delivery of these targeted therapies more effectively, potentially leading to better outcomes for a larger group of patients.
Rethinking Standard of Care
The study also highlights the need to reevaluate current treatment strategies and consider the integration of new imaging technologies into standard clinical care. While PSMA-PET is becoming more widely adopted, its use is not yet universal, and its role in routine staging for all prostate cancer patients is still being defined. This research provides compelling evidence for its utility, particularly in high-risk cases.
"It also highlights the need to reevaluate treatment strategies and opens the door to potentially curative options for some patients, such as targeted radiotherapy, while raising important questions about integrating new imaging technologies into standard care," the article states. The transition from traditional imaging to advanced modalities like PSMA-PET requires a shift in clinical practice, education, and potentially reimbursement policies.
The Path Forward: Ongoing Research and Future Directions
The UCLA researchers acknowledge that while their findings are significant, further research is essential to fully understand the impact of PSMA-PET on patient outcomes.
"While the current findings underscore PSMA-PET’s potential, researchers are continuing to explore its broader applications through additional studies," the article notes. "More research is needed to understand its impact on long-term patient outcomes and how it can best guide therapy," Dr. Calais emphasized.
Dr. Holzgreve echoed this sentiment, stating, "We have good rationales to assume that it is helpful to primarily rely on PSMA-PET findings. But more high-quality prospective data would be needed to claim superiority of PSMA-PET for treatment-guidance in terms of patient outcome. However, we are confident PSMA-PET will continue to advance prostate cancer staging and guide personalized therapies."
UCLA is actively pursuing this further research. Current efforts include analyzing follow-up data from four UCLA-led trials to assess how PSMA-PET findings have influenced treatment decisions and, ultimately, patient outcomes. Furthermore, the team is participating in an international consortium that is examining over 6,000 patients to investigate the prognostic value of PSMA-PET – its ability to predict the likely course of the disease.
Background Context: The Evolving Landscape of Prostate Cancer Treatment
Prostate cancer is the most common cancer diagnosed in men in the United States, excluding skin cancer, and the second leading cause of cancer death among men. For decades, the management of prostate cancer has been a dynamic field, with continuous advancements in understanding its biology, detection, and treatment.
Hormone-sensitive prostate cancer refers to prostate cancer that still responds to treatments that lower testosterone levels. Testosterone fuels the growth of prostate cancer cells. Androgen deprivation therapy (ADT) is the cornerstone of treatment for advanced hormone-sensitive prostate cancer, aiming to reduce testosterone levels. However, over time, many prostate cancers can become resistant to ADT, evolving into castration-resistant prostate cancer, which is more aggressive and harder to treat.
The classification of prostate cancer as "nonmetastatic" versus "metastatic" is a critical distinction. Nonmetastatic disease implies that the cancer is confined to the prostate or has spread only to nearby lymph nodes. Metastatic disease means the cancer has spread to distant parts of the body, such as bones or other organs. This distinction significantly influences treatment choices and prognosis.
The development of more sensitive imaging techniques has been a major focus in improving prostate cancer management. Traditional imaging methods, while useful, have limitations in detecting very small or early metastases. The advent of PSMA-PET imaging represents a significant paradigm shift, offering unprecedented visualization of prostate cancer spread.
The EMBARK trial, mentioned in the study, is a prime example of how clinical research has driven progress. Its findings on the benefit of adding enzalutamide to ADT have become a standard of care for many patients with high-risk nonmetastatic hormone-sensitive prostate cancer. However, this new UCLA study suggests that the patient populations in such trials may have been more heterogeneous than previously assumed, prompting a critical re-examination of trial design and interpretation.
Conclusion: A Call for Enhanced Diagnostic Accuracy
The UCLA Health study serves as a potent reminder that scientific understanding is constantly evolving. The findings underscore the critical need for advanced diagnostic tools like PSMA-PET imaging to ensure accurate staging of prostate cancer. By revealing the true extent of disease, PSMA-PET has the potential to optimize treatment decisions, improve patient outcomes, and pave the way for more effective and personalized therapies in the fight against prostate cancer. The ongoing research at UCLA and elsewhere will be crucial in solidifying the role of PSMA-PET in routine clinical practice and further refining its application in this challenging disease.
