Long-Term Data Validates IsoPSA for Prostate Cancer Risk Stratification
Conceptual image for prostate cancer treatment: © Dr_Microbe - stock.adobe.com
The IsoPSA prostate cancer test has shown to reliably maintain risk stratification over 30 months, with low-risk patients with prostate cancer remaining stable. This reinforces its value in both early detection and active surveillance strategies.1
Compared with traditional prostate-specific antigen (PSA) testing, IsoPSA offers significantly improved specificity, helping clinicians reduce unnecessary prostate biopsies by up to 50%. According to Jason M. Hafron, MD, IsoPSA is easy to use in everyday clinical practice and shows particular benefit in community settings, where advanced imaging interpretation may be limited.
“The beauty of IsoPSA is its simplicity. It’s very easy to use in the clinic on a day-to-day basis,” Hafron, chief medical officer and medical director of clinical research at the Michigan Institute of Urology, as well as a professor of urology at the William Beaumont School of Medicine at Oakland University, explained in an interview with Targeted Oncology.
These findings come from a single-center retrospective review of 1578 patients who underwent IsoPSA testing from November 2016 to August 2022. A total of 541 patients had initial low IsoPSA indices (≤6), and among them, 23 (4.3%) were diagnosed with clinically significant prostate cancer (csPCa) on a subsequent biopsy. Of the 541 patients, 204 had an MRI, of which 48 (23.5%) showed suspicious lesions. A total of 366 (35.3%) of the 1037 patients with initial high IsoPSA indices were diagnosed with csPCa on a subsequent biopsy, and 712 of the 1037 patients had an MRI, of which 342 (48.0%) showed suspicious lesions.
The risk of developing csPCa after 12, 24, and 30 months, respectively, was 0.4% (95% CI, 0.1%-1.6%), 2.5% (1.4%-4.4%), and 6.3% (4%-9.6%) in patients with low IsoPSA indices vs 5.9% (4.6%-7.6%), 31.7% (28.3%-35.4%), and 49.5% (45.3%-53.9%) in patients with high IsoPSA indices. Overall, these data showed that the risk of developing csPCa was smaller in patients with initial low vs high IsoPSA indices over the 30 months. These findings further support the use of IsoPSA to safely avoid follow-up testing in these patients.
In the interview, Hafron highlighted newly released longitudinal data confirming the durability of the IsoPSA test.
A close-up of a microscope lens capturing a vibrant blue cancer cell, symbolizing the groundbreaking findings: © catalin - stock.adobe.com
Targeted Oncology: Can you provide some giving background on the IsoPSA prostate cancer test?
Hafron: IsoPSA is a serum-based test that is indicated for [patients] with a PSA greater than 4 and age greater than 50. It's for [patients] who are suspected of having prostate cancer. We've been using the test since 2018. We were involved in a lot of the initial validation trials and have been using it clinically and commercially for many years now.
What were the key findings from the newly released longitudinal data?
I think the longitudinal data supports what previous studies on IsoPSA have shown. The key is that what we see initially on the IsoPSA test is maintained over time. So, if a patient is low risk for clinically significant prostate cancer, that holds up over the next 30 months. If they're low, they're going to stay low. That speaks to the durability and strength of the IsoPSA test.
How does this improve on traditional PSA testing?
Traditional PSA testing is inadequate. We've known that for many years—it lacks specificity. It's led us to biopsy too many patients and caused significant anxiety and distress. Now, with IsoPSA, we can define who needs a biopsy and who doesn’t. We can define who needs an MRI, or we can order it simultaneously with an MRI. Based on previous publications, IsoPSA reduces unnecessary biopsies by up to 50%.
Were there any insights on the follow-up data regarding its ability to predict progression or stability of prostate disease in patients under active surveillance?
What it shows is that there’s potential to use IsoPSA in that space. It’s not currently approved for that use, but IsoPSA detects clinically significant prostate cancer. So, if there’s a change in the IsoPSA score, that could indicate a change in the disease. This would need to be further studied, but it may signal disease progression requiring active treatment.
How might these data influence clinical decision-making?
The beauty of IsoPSA is its simplicity. It’s very easy to use in the clinic on a day-to-day basis. The results are straightforward: if it’s less than 6, we can monitor the patient. Based on the recent Abdallah data, if they’re low, their risk over the next 30 months for clinically significant prostate cancer is about 5%. That changes how I talk to patients—I’m confident that a low or negative IsoPSA means it’s unlikely they have clinically significant disease.
It also changes how I monitor them. If they have a low IsoPSA, I don’t need to see them as frequently or check PSA as often. I can be less intensive with monitoring. But if a patient has a high IsoPSA, as we've seen in the Abdallah data, they’re at about 35% risk for clinically significant prostate cancer. Those patients need to be followed closely, and treatment needs to be tailored accordingly.
How do you see this potentially influencing their day-to-day practice?
In the community, biomarkers are very helpful. There’s a lot of heterogeneity in the quality of multiparametric MRI interpretation. A lot of the published data comes from high-level specialists, which isn’t always reflective of the community setting. Community radiologists are often reading multiple types of solid tumors, and prostate MRI is very hard to interpret. So, a great equalizer or solution is to use biomarker testing to further evaluate and stratify risk in patients with elevated PSA.
The key takeaway is that a patient with an elevated PSA should at least have a biomarker test or a multiparametric MRI. In our practice, we encourage using both. PSA alone is no longer adequate to determine if a patient needs a prostate biopsy.
