Koo Looks to the Future With PSMA PET Imaging in Prostate Cancer

Phillip J. Koo, MD

Broad application of precision imaging with prostate-specific membrane antigen (PSMA) PET, although enticing because of its increased sensitivity and specificity compared with conventional imaging, should be cautioned against, according to Phillip J. Koo, MD. Koo added that until more research is done to understand which patient populations stand to benefit the most from the tool, discerning whether to use it or not boils down to one question: Will the result change my treatment recommendation?

“PSMA PET is a wonderful tool, we all know that and agree, but the take home message is let’s be careful when we use it. [When looking at] using it in every clinical setting [and] for treatment response today, in general, [I should note that] the overutilization of this tool isn’t necessarily a good thing. We have to be more thoughtful regarding how we use it. Deploy the tool where it’s most effective and grow it from there. There’s always a temptation because it’s ‘a better tool’ to start using it as often as possible and I am often a victim of that as well. We need to step back, be a bit more thoughtful, and try to follow the appropriate guidelines that are published by multiple different societies,” Koo said in an interview with OncLive®.

In a presentation at the 17th Annual Interdisciplinary Prostate Cancer Congress® and Other Genitourinary Malignancies (NY GU) in New York, New York, Koo stated that prostate cancer will progress in approximately 30% to 40% of patients after initial treatment, and molecular targeted imaging with tools such as PSMA PET may lead to a change in diagnostic approaches and management. Koo cited a prospective phase 3 imaging trial that evaluated the diagnostic efficacy of 68Ga-PSMA-11 in patients with intermediate- to high-risk prostate cancer considered for prostatectomy (n = 764) across three academic centers (NCT03368547; NCT02611882; and NCT02919111). The results revealed a sensitivity of 40% (95% CI, 34%-46%) and specificity of 95% (95% CI, 92%-97%) for the detection of pelvic nodal metastases.^1,2

In the interview, Koo,chief of Diagnostic Imaging at Banner MD Anderson Cancer Center in Phoenix, Arizona, detailed future directions for PSMA PET and advantages of the imaging tool.

OncLive: How is next-generation imaging defined in prostate cancer and what are the advantages of the technique?

Koo: The terminology that we’re using for advanced PET imaging is evolving. Originally, we coined it as next-generation imaging. Now the RADAR VI article that was published in the Journal Urology Open [Plus] changed it to molecular targeted imaging to reflect the fact that it’s no longer next generation—it’s here, should be used, and is becoming the standard of care.

As we’re all familiar with, prostate cancer cells overexpress PSMA and we’re learning that PSMA PET is much better with regards to accuracy and ability to detect disease at lower prostate-specific antigen levels. [These are] 2 pieces that help us advance the field and know more about the patient’s true status with regards to the disease than tools in the past have given us.

Are there any situations where PSMA PET wouldn’t be suitable or the ‘old imaging ways’ would be better?

This is a question that comes up all the time, whether conventional imaging or traditional imaging is obsolete. My take on it is conventional imaging and traditional imaging were used in all the landmark trials that led to certain drug approvals. For us to replicate those findings we should ideally try to follow the inclusion criteria and the protocols as closely as possible. That’s not always realistic, so in certain contexts, we need to balance the use of both and figure out what’s best for those patients.

My advice to physicians is often to think of things [by] doing a bit of a reverse engineering approach to decision-making. Depending on what the answer is, how would that affect how you manage that patient, and in the end if the results of a PSMA PET aren’t going to change how you manage the patient then what is the true value of it? I would challenge everyone to think about it from a different perspective and then make decisions based on how they would react to the results of that test.

What does the future hold for PSMA PET?

With regards to PSMA PET on the diagnostic side, there are trials exploring different types of isotopes using copper compounds and whatnot that might change the paradigm and how we image patients. That’s exciting because potentially there might be differences that are meaningful with regards to clinical management and outcomes that we need to study further.

The other exciting part is radioligand therapies. Dr Scott T. Tagawa, MD, MS, FACP, FASCO, [spoke] about radiopharmaceuticals here at NY GU and we’re seeing that our trials are now using radioligand therapies earlier in the course of treatment, pre-chemotherapy, and then perhaps in the hormone-sensitive space.

What’s also [interesting] to me is [figuring out] how to use PSMA PET to better select patients. Some trials will start looking at this data, whether they’re prospective, retrospective, or real-world evidence trials that look at how to use more than just a plus-minus type of approach to select patients and dig deeper into what the imaging is telling us.

Were there any other NY GU sessions that caught your eye?

There were so many different sessions that caught my eye—in general, prostate cancer is a success story. Looking back on the past 10 to 15 years, the number of therapies that are now available for patients has expanded and multiplied. Oftentimes, [the armamentarium] is referred to as an embarrassment of riches. But it’s a story of hope for patients [because] patients who have advanced disease have more options and are living longer. It’s up to us to figure out how to maximize the benefits of all these different therapies because deep down we all believe that receiving more of these therapies will help patients live a longer and better life.

References

1. Koo PJ. Appropriate use of molecular targeted imaging in prostate cancer.Presented at: 17th Annual Interdisciplinary Prostate Cancer Congress® and Other Genitourinary Malignancies; March 8-9, 2024. New York, NY.
2. Hope TA, Eiber M, Armstrong WR, et al. Diagnostic accuracy of 68Ga-PSMA-11 PET for pelvic nodal metastasis detection prior to radical prostatectomy and pelvic lymph node dissection: a multicenter prospective phase 3 imaging trial. JAMA Oncol. 2021;7(11):1635-1642. doi:10.1001/jamaoncol.2021.3771