FDG PET/CT brings accuracy to staging, restaging of prostate cancer

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CHICAGO—FDG PET/CT may add significant value in patients with prostate cancer by accurately identifying primary lesions and/or metastases at initial staging and detecting recurrent disease, according to results presented Sunday during the Nuclear Medicine scientific sessions at the 94th annual meeting of the Radiological Society of North America (RSNA).

Recently published data from the National Oncologic PET Registry (NOPR) revealed that prostate cancer (PC) represented 11.7 percent of patients enrolled in the NOPR. The aim was to evaluate the still controversial role of FDG PET/CT in staging and restaging of PC, according to the authors.

For the study, presented by Nghi C. Nguyen, MD, PhD, assistant professor of radiology at St. Louis University in Missouri, a total of 50 PC patients underwent FDG PET/CT scans; 21 for staging and 29 for restaging. PSA recurrence (PSA+) as recurrent disease was defined as: PSA>0.4 in patients with prior radical prostatectomy or PSA>1 in patients with prior hormonal/chemo/radiation therapy. The scans were reviewed by two nuclear medicine physicians; a consensus for equivocal findings was obtained via a third reader. Histopathology, clinical or imaging follow-up served as reference standard.

According to the results, PET/CT correctly identified FDG-avid PC and/or metastases in 48 percent of patients selected for staging, including detection of primary PC in 9 and metastatic lesions in three patients. Overall, PET/CT was false negative in the remaining 42 percent.

Of the 29 patients selected for restaging, three were tumor free (PSA-), whereas the remaining 26 patients were clinically suspicious for having recurrent disease (PSA+). PET/CT was true negative in all three patients with PSA- level. Of the 26 patients with PSA+, PET/CT was false negative in 35 percent and suspicious for cancer in the remaining 17 65 percent. Of those 17 patients with PET suspicious lesions, six patients had no follow up, whereas malignancy was confirmed in 42 percent. Of the total 50 PC patients, PET/CT revealed findings suspicious for a second, previously unknown, primary in 8 percent. Lung cancer was confirmed in one case; but, the remaining three are yet without confirmation, the researchers noted.

“FDG PET/CT may add significant value in patients with prostate cancer by accurately identifying primary lesions and/or metastases in 48 percent at initial staging, detecting recurrent disease in PSA+ patients in 42 percent as well as incidentally diagnosing a second primary in at least 2 percent,” the authors concluded.