FDG-PET Scans May Improve Prostate Cancer Management

FDG-PET images may indicate which patients have high-grade prostate cancer.
FDG-PET images may indicate which patients have high-grade prostate cancer.

NIAGARA FALLS, Ont.—Fluorodeoxyglucose positron emission tomography (FDG-PET) findings can help identify prostate cancer (PCa) patients who have high-risk disease prior to radical prostatectomy and are at elevated risk for treatment failure, researchers reported at the Canadian Urological Association's 68th annual meeting.

Lead investigator Frederic Pouliot, MD, PhD, a urologic oncologist at Laval University in Quebec, and his team found that increased FDG uptake by the prostate is highly correlated with factors indicative of a poor prognosis such as advanced clinical stage, a pathological Gleason score of 8 or higher, and percentage of intraprostatic cancer.

They also found it strongly parallels patients' likelihood of five-year progression-free survival based on two of the most highly regarded PCa nomograms, the pre-treatment nomogram from Memorial Sloan-Kettering Cancer Center (MSKCC) in New York and the Cancer of the Prostate Risk Assessment (CAPRA) – S (CAPRA-S) post-radical-prostatectomy nomogram from the University of California San Francisco.

“You could use FDG-PET before you operate on patients to help determine their management,” Dr. Pouliot said. “Since there is a high failure rate with prostatectomy, the presence or absence of FDG uptake can help you decide whether to still do a radical prostatectomy in a morbid patient or just reorient the patient to radiation therapy or androgen deprivation therapy.”

The researchers analyzed data from 54 patients with Gleason 8 or higher PCa who underwent FDG-PET. Forty-one also had radical prostatectomy and extended pelvic lymph node dissection and the remaining 13 underwent non-operative management with androgen deprivation therapy and/or radiotherapy, or both. The team compared the findings from FDG-PET to those at surgery.

Increased FDG uptake occurred in 44%, 13% and 6% of patients' prostates, lymph nodes, and bones, respectively. It had a 27% sensitivity for detecting lymph node metastases, but a specificity and positive predictive value of 100%.

Increased FDG-PET uptake provided statistically significant correlations with a range of negative prognostic factors, including clinical stage and Gleason score. Furthermore, it predicted pathologic Gleason score: 81.8% of patients with increased FDG uptake had a pathologic Gleason score of 8 or higher at radical prostatectomy and none were downstaged to Gleason 6 or 7.

In addition, none of the patients with increased FDG uptake had a post-prostatectomy Gleason pattern of 3 + 3, 3 + 4, or 3 + 5. Most had a pattern of 4 + 3, 4 + 4 and 4 + 5, and one had a 5 + 4 pattern.

“So without operating on your patients you can know whether it's a real Gleason 8 or whether they will be downstaged to less than 8 on prostatectomy,” Dr. Pouliot explained.

When the investigators entered the patients' disease characteristics into nomograms, they found a 70.2% probability of five-year progression-free survival with CAPRA-S among patients without increased FDG uptake and a 91.5% probability with the MSKCC nomogram. The respective probabilities among patients with increased FDG uptake were 26.9% and 72.0%.

They concluded that FDG-PET may identify patients with a higher risk of biochemical failure following local treatment.

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