PSMA-PET/CT Outpaces Conventional Imaging with High-Risk Prostate Cancer Detection

Switching to a more advanced imaging technique can improve detection, disease staging, and tailoring of treatment in patients with aggressive prostate cancer, according to industry experts.

In a new study, published March 22 in Lancet, led by Michael S. Hofman, MBBS, with the Peter MacCallum Cancer Center in Australia, investigators determined using a molecular imaging technique, known as PSMA PET/CT, does a better job at identifying molecules associated with prostate cancer and in determining how much the disease has already spread at the time of diagnosis. And, it reaches this goal with less than half the radiation dose – 8.4 mSv vs. 19.2 mSv, respectively.

“Taken together, our findings indicate that PSMA-PET/CT scans offer greater accuracy than conventional imaging and can better inform treatment decisions,” Hoffman said in a press statement. “We recommend that clinical guidelines should be updated to include PSMA-PET/CT as part of the diagnostic pathway for men with high-risk prostate cancer.”

With this technique, patients were given a radioactive substance that detects Prostate Specific Membrane Antigen (PSMA), high levels of which are found in prostate cancer cells. Then, they underwent a PET/CT scan – the CT produced detailed images of body organs and structures while the PET lit up where PSMA was present in high quantities.

While the study didn’t look at whether using molecular imaging could actually impact patient survival, the results, he said, could help doctors determine whether to use localized treatment, such as surgery or radiotherapy, or more advanced treatments that would affect the patient’s entire body.

What the Study Found

To determine the efficacy of PSMA-PET/CT, investigators divided 300 men into two groups – 152 received conventional CT and bone scans, and 148 received PSMA-PET/CT. They, then, swapped and received the alternate form of scanning unless they had more than three metastases on their initial scan.

Based on results PSMA-PET/CT proved to be almost one-third more accurate in identifying the spread of prostate cancer throughout a patient’s body. The molecular imaging was 92-percent accurate versus 65-percent accuracy with standard imaging. Not only was PSMA-PET/CT better at detecting small sites of tumor spread, but it also provided false negatives in only six cases. In contrast, conventional imaging failed to detect metastasis in 29 patients.

Impact on Treatment

In addition to improving detection, PSMA-PET/CT also had a significant impact on a patient’s treatment plan and disease management. According to senior author Declan Murphy, the effect could be greatly beneficial.

“Around one in three prostate cancer patients will experience a disease relapse after surgery or radiotherapy. This is partly because current medical imaging techniques often fail to detect when the cancer has spread, which means some men are not given the additional treatments they need,” he said. “Our findings suggest PSMA-PET/CT could help identify these men sooner, so they get the most appropriate care.”

According to the study results, treatment plans were changed in 28 percent of men who received PSMA-PET/CT. Only 15 percent of men with conventional imaging saw any alterations in their care plan. The effect remained even when PSMA-PET/CT was used as a second-round screening – 27 percent of patients had treatment plan changes after additional PSMA-PET/CT imaging, and only 5 percent saw changes with conventional imaging.

Is It Feasible?

But, simply because PSMA-PET/CT does a better job at detection and diagnosing metastases than current conventional methods, that doesn’t mean all patient-care environments can necessarily implement it. Cost will likely play a large role in whether patients will have wide-spread access to the scans.

“Costs associated with PSMA-PET/CT vary in different regions of the world, but this approach may offer savings over conventional imaging techniques,” said co-author Roslyn Francis with the University of Western Australia. “A full health-economic analysis will help to determine the cost effectiveness of introducing PSMA-PET/CT, both from a patient and a healthcare perspective.”

Completing an economic analysis will be critical, Caroline Moore, professor of urology at the University College London, wrote in accompanying editorial.

“Introduction of novel imaging into routine practice requires careful assessment of the potential burden to both individuals and to society, taking into account change in treatment which can result,” Moore wrote. “The proPSMA authors have planned an economic analysis of the potential effect of replacing conventional staging with PSMA-PET, which will be crucial in assessing the feasibility of widespread use of PSMA-PET/CT in men being considered for radical treatment for high-risk prostate cancer.”