CHICAGO – PET/CT scans in patients treated for prostate cancer can detect early progression of the disease, despite undetectable prostate-specific antigen (PSA) levels, according to a study presented December 2 at RSNA.
The finding is from a retrospective analysis of prostate-specific membrane antigen (PSMA) PET/CT imaging in 2,141 patients with disease progression in whom 257 (12%) patients were identified as “PSA zero,” noted presenter Yalda Nikanpour, MD, of the Mayo Clinic in Rochester, MN.
“Prostate cancer, particularly in [castrate-resistant prostate cancer], can occur even without detectable PSA levels,” she said.
Prostate cancer is among the most frequently diagnosed cancers in men worldwide. Up to 20% of patients progressing to castration-resistant prostate cancer (CRPC) within five years. PSA is a critical blood biomarker for detecting and managing the disease, with low or undetectable PSA levels traditionally indicating good therapeutic control.
However, prostate cancer tumors can progress while secreting little or no PSA, which highlights the limitations of PSA as the sole monitoring tool, Nikanpour noted.
Thus, to inform better treatment strategies for patients, the group analyzed data from a PSMA-PET registry at the Mayo Clinic to clarify the clinical implications of PSA discordance. They classified patients into two groups according to disease status, either hormone-sensitive prostate cancer (HSPC) or castration-resistant prostate cancer (CRPC), as well as calculated overall survival for the different groups.
Out of 2,141 patients diagnosed with disease progression on PSMA-PET scans, the researchers identified 257 (12%) who were PSA zero. More than 60% of these patients presented initially with localized prostate cancer while the rest (39%) had de-novo metastatic disease (more aggressive and faster developing) cases.
Of the 257 patients, the majority (95%) had received at least one systemic therapy prior to being PSA zero. Over a median time of 119 months between the initial prostate cancer diagnosis and recurrence despite being PSA zero, 184 (72%) patients progressed to CRPC. In addition, over a median period of 6.7 months, one patient in the HSPC PSA zero group. Over a median of 8.9 months, 12 PSA zero patients died.
“In prostate cancer management, the undetectable PSA level does not guarantee the absence of disease progression, emphasizing the ongoing need for frequent monitoring of the disease with the PSMA PET/CT technique,” Nikanpour concluded.
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