Carcinoma Prostate - PET/CT

63 year old male patient operated for carcinoma prostate came for FDG PET/CT evaluation for recurrent tumor. Coronal CT and the PET/CT fused image showing non FDG avid multiple sclerotic lesions in the sacrum and right iliac bones. Multiple similar lesions also were seen in various vertebral bodies, scapulae and ribs (not shows here)

Discussion:

PET/CT in combination with PSA levels can play a significant role in detecting and staging prostate cancer. Although Prostate-specific antigen measurements are considered a useful organ-specific marker, but they are alone not necessarily an adequate tumor marker.

Localized disease within the prostate and pelvic lymph nodes can be difficult to image with PET/CT because of the proximity of bladder activity as there is will be spillover of radiotracer uptake.  

The radiotracers used in prostate PET/CT: 

1. Fluorodeoxyglucose (FDG): have a role in the detection of lymph node metastases, particularly in patients with relapsed disease after primary treatment. The sensitivity is around 50%. FDG-PET has an excellent detection rate for lytic skeletal metastases, but it has a poor detection rate for sclerotic metastases as in our case.
2. Carbon 11 (C11)–acetate and C11-choline (18F-Choline): Shown promising alternative but they are less readily available and still under assessment. Few recent studies have showed conflicting results as one study says there is relative high rate of false-negative results as prostatic disorders other than cancer may accumulate 11C-choline. Some other study shows C11-choline PET/CT can differential prostate carcinoma from benign hyperplasia, chronic prostatitis, or normal prostate tissue. The C11 choline has shows promising results in staging of the tumor; however it still needs more studies.

To conclude sextant /10 core biopsy along with PSA are the mainstay of diagnosis and FDG PET/CT and C11 Choline PET/CT are for the staging, treatment planning and response evaluation.