Radiology: PET/CT can detect recurrent prostate cancer

Images in a patient who had undergone radical prostatectomy (PSA level, 2.97 ng/mL). Transverse PET and fused PET/CT scans obtained with anti-3-18F-FACBC. SPECT and fused SPECT/CT scans obtained with 111In–capromab pendetide. Image source: Radiology 2011;259(3):852-861.

The synthetic amino acid analog radiotracer anti-1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid (anti-3-¹⁸F-FACBC) with PET/CT is more sensitive than ¹¹¹In-capromab pendetide in the detection of recurrent prostate carcinoma.

Prostate carcinoma is the second leading cause of death in men in the U.S., with 32,050 estimated deaths in 2010. Although approximately 30 percent of patients will experience recurrence of elevated prostate-specific antigen (PSA) levels, those with biochemical failure may not manifest clinical disease, according to David M. Schuster, MD, from the department of radiology at Emory University Hospital in Atlanta, and colleagues.

The authors wrote, “PSA level in isolation is not an adequate end point and must be correlated in clinical context. Even an increase in PSA level after prostatectomy does not necessarily equate with clinical failure.” They added there is no ideal method with which to establish truth in all circumstances, as reflected in the acceptable practice variations in the restaging of patients with prostate carcinoma, and therefore, the researchers chose to default to biopsy findings.

In conducting this study, they set out to compare the diagnostic performance of the synthetic amino acid analog radiotracer anti-3-¹⁸F-FACBC with that of ¹¹¹In–capromab pendetide in the detection of recurrent prostate carcinoma.

In a study of 50 patients (mean age, 68.3 years; age range, 50 to 90 years), the researchers found that amino acid transport as characterized with anti-3-¹⁸F-FACBC PET/CT depicted local recurrence with a sensitivity of 89 percent, whereas conventional imaging with ¹¹¹In-capromab pendetide SPECT/CT had a sensitivity of 69 percent.

In the detection of extraprostatic recurrent disease, anti-3-¹⁸F-FACBC PET/CT had 100 percent sensitivity, a specificity of 100 percent and an accuracy of 100 percent. Comparatively, ¹¹¹In-capromab pendetide SPECT/CT had 10 percent sensitivity, specificity of 100 percent and accuracy of 47 percent. 

Schuster and colleagues concluded that anti-3-¹⁸F-FACBC PET/CT is also highly accurate in differentiating prostatic from extraprostatic disease and can be used to accurately restage prostate cancer.

However, the authors noted that direct comparisons of anti-3-¹⁸F-FACBC PET/CT to “other promising imaging techniques, such as choline PET/CT and/or advanced MRI, ideally with use of the patient as his own control in a multicenter environment, should be carried out before clinical recommendations can be made.”