Tag: PSA screening

All-Star AI for Prostate MRI

Posted on by Brian Casey

An AI model for prostate MRI that combines the best features of five separate algorithms helped radiologists diagnose clinically significant prostate cancer in a new study in JAMA Network Open. 

The Prostate Imaging-Cancer AI consortium was formed to address a nagging problem in prostate cancer screening.

  • Studies have shown that MRI can reduce biopsies and minimize workup of clinically insignificant disease, but it also has high inter-reader variability and requires a high level of expertise. 

The PI-CAI challenge brought together researchers from multiple countries with a single goal: develop an AI algorithm for prostate MRI that would improve radiologists’ performance.

  • Results were presented at RSNA and ECR conferences, as well as in a 2024 paper in Lancet Oncology that showed that individually the algorithms improved radiologist performance and generated fewer false positives.

But what if you combined the best of the PI-CAI algorithms into a single all-star AI model? 

  • Researchers did just that in the new study, combining the top five algorithms from the PI-CAI challenge into a single AI model in which each algorithm’s results were pooled to create an average detection map indicating the presence of prostate cancer. 

To test the new algorithm, 61 readers from 17 countries interpreted 360 prostate MRI scans with and without the model. 

  • Patients in the test cohort had a median age of 65 years and a median PSA level of 7.0 ng/mL; 34% were eventually diagnosed with clinically significant prostate cancer.

Results of PI-CAI-aided prostate MRI were as follows …

  • Radiologists using the algorithm had higher diagnostic performance than those who didn’t (AUROC=0.92 vs. 0.88).
  • PI-CAI working on its own had the highest performance (AUROC=0.95).
  • Sensitivity improved for cases rated as PI-RADS 3 or higher (97% vs. 94%).
  • Specificity also improved (50% vs. 48%).
  • AI assistance improved the performance of non-expert readers more than expert readers, with greater increases in sensitivity (3.7% vs. 1.5%) and specificity (4.3% vs. 2.8%).

The Takeaway

The new PC-CAI study is an important advance not only for prostate cancer diagnosis but also for the broader AI industry. It points to a future where multiple AI algorithms could be combined to tackle clinical challenges with better diagnostic performance than any model working alone.

MRI Reduces Prostate Biopsies

Posted on by Brian Casey

New research provides additional support for MRI’s role in making prostate screening more effective. In a new study in NEJM, researchers found that MRI can help reduce unnecessary biopsies more than 50%, with a very low chance of missing high-risk disease. 

As we’ve discussed in previous newsletters, prostate cancer screening based on PSA levels is an imprecise test. 

  • Many men with suspiciously high PSA (typically 3-4 ng/mL or higher) undergo biopsies that detect clinically insignificant disease that would never present a health risk during their lifetimes – the classic definition of overdiagnosis. 

Adding MRI can help make prostate screening more precise by directing biopsy-based workup to only those men with clinically significant cancer – but questions still abound about exactly when it should be used. 

In new results from the GÖTEBORG-2 trial in Sweden, researchers compared prostate screening protocols in men with PSA levels 3 ng/mL and higher who got MRI scans:

  • One group automatically got systemic biopsy and then MRI-targeted biopsy based on MRI results.
  • The other group only got MRI-targeted biopsy if they had a suspicious MRI scan.

In 13.2k men who were followed up for a median of four years, researchers found that those in whom systemic biopsy was omitted …

  • Had 57% lower risk of clinically insignificant cancers.
  • Had lower relative risk of clinically insignificant cancers in subsequent screening rounds (RR=0.25 vs. 0.49).
  • Had 16% lower risk of detecting clinically significant cancers.
  • Had 35% lower risk of advanced or high-risk cancers.

On the down side, the protocol eliminating systemic biopsy could lead to later diagnoses for higher-risk disease for 3 in 1k men – but given the slow-growing nature of prostate cancer it’s not clear how significant this is. 

  • Also, the data indicate that “most prostate cancers become visible on MRI” before they are incurable, which increases the likelihood that they would at least be detected on subsequent screening rounds and could be treated effectively.

The Takeaway

The new findings should help clinicians hone in on the best prostate screening protocols for maximizing detection of clinically significant cancer while minimizing unnecessary workup. Hopefully, the addition of new technologies like AI can move this process along.

Better Prostate MRI with AI

Posted on by Brian Casey

A homegrown AI algorithm was able to detect clinically significant prostate cancer on MRI scans with the same accuracy as experienced radiologists. In a new study in Radiology, researchers say the algorithm could improve radiologists’ ability to detect prostate cancer on MRI, with fewer false positives.

In past issues of The Imaging Wire, we’ve discussed the need to improve on existing tools like PSA tests to make prostate cancer screening more precise with fewer false positives and less need for patient work-up.

  • Adding MRI to prostate screening protocols is a step forward, but MRI is an expensive technology that requires experienced radiologists to interpret.

Could AI help? In the new study, researchers tested a deep learning algorithm developed at the Mayo Clinic to detect clinically significant prostate cancer on multiparametric (mpMRI) scans.

  • In an interesting wrinkle, the Mayo algorithm does not indicate tumor location, so a second algorithm – called Grad-CAM – was employed to localize tumors.

The Mayo algorithm was trained on a population of 5k patients with a cancer prevalence similar to a screening population, then tested in an external test set of 204 patients, finding …

  • No statistically significant difference in performance between the Mayo algorithm and radiologists based on AUC (0.86 vs. 0.84, p=0.68)
  • The highest AUC was with the combination of AI and radiologists (0.89, p<0.001)
  • The Grad-CAM algorithm was accurate in localizing 56 of 58 true-positive exams

An editorial noted that the study employed the Mayo algorithm on multiparametric MRI exams.

  • Prostate cancer imaging is moving from mpMRI toward biparametric MRI (bpMRI) due to its faster scan times and lack of contrast, and if validated on bpMRI, AI’s impact could be even more dramatic.

The Takeaway
The current study illustrates the exciting developments underway to make prostate imaging more accurate and easier to perform. They also support the technology evolution that could one day make prostate cancer screening a more widely accepted test.

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