Is PSMA PET/CT More Beneficial than Bone Scintigraphy in Detecting Bone Lesions in Cases of High-Risk Prostate Cancer?

A new comparative study found the use of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) led to treatment changes in nearly 20 percent of patients with high-risk prostate cancer.

Emerging research suggests that prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) could have a significant advantage over bone scintigraphy in the staging of patients with high-risk prostate cancer.

In a prospective, multicenter study, published in Urologic Oncology: Seminars and Original Investigations, researchers compared the use of 18F-PSMA PET/CT to initial bone scintigraphy for the detection of bone lesions in 79 patients with primary high-risk prostate cancer. According to the study, Group 1 was comprised of 70 patients who had no evidence of metastasis on bone scintigraphy and Group 2 consisted of nine patients deemed to have low-volume metastatic disease, which researchers defined as less than four bone metastases, no visceral metastases, and an absence of metastases outside the pelvis or vertebral column as per CHAARTED criteria.

The researchers found that 18F-PSMA PET/CT revealed bone metastases in 12.8 percent (nine of 70) of Group 1 patients, all of whom had negative bone scintigraphy results. For the nine Group 2 patients, 18F-PSMA PET/CT resulted in upstaging of four patients (44.4 percent) to high-volume metastatic disease and downstaging of two patients (11.1 percent) after a lack of bone lesion detection, according to the study authors.

The study authors pointed out that the findings with 18F-PSMA PET/CT led to changes in planned treatment for 14.3 percent of Group 1 patients and 66.7 percent of Group 2 patients.

“In the present study, we found that in almost 20% of (the overall) patients, the results of 18F-PSMA PET/CT imaging changed the intended treatment advice due to either upstaging or downstaging of disease. This could have major consequences for these patients,” wrote study co-author Yves J.L. Bodar, M.D., who is affiliated with the Department of Urology and the Department of Radiology and Nuclear Medicine at Amsterdam University Medical Centres in Noord Holland, the Netherlands, and colleagues. “Those who are upstaged may undergo (palliative) systematic therapy more often instead of treatment with curative intent whereas those who are downstaged (may have treatment with curative intent more often).”

While noting that the impact of the treatment plan changes in the study is currently unknown, Bodar and colleagues said the findings from the study, reportedly the first prospective, multicenter trial to compare bone lesion detection rates of bone scintigraphy and 18F-PSMA PET/CT in prostate cancer, could go a long way toward facilitating improved staging and risk stratification in this high-risk population.

In regard to study limitations, the researchers acknowledged that the use of different 18F-PSMA tracers and different scanning protocols may have had an impact on the study findings. They also noted a small number of patients in the low-volume metastasis group and a lack of local and distant lymph node staging.