Prostate Cancer

Fast Facts:

• Most common cancer of US men (1:7)
• 2nd leading cause of cancer death for US men
• Stage I & 2: 5-yr survival > 95%

Normal Prostatic Uptake:  

• The normal prostate typically demonstrates little or no FDG uptake.
• Mild diffuse prostate uptake is considered normal.
• Moderate or intense diffuse uptake typically reflects prostatitis.
• Although even focal FDG uptake in the prostate is often normal, correlation with PSA levels is advised, especially if the uptake is located in the peripheral zone (location of 70% of prostate cancers).  
• Uptake centrally in the gland typically represents normal hypermetabolic urine in the prostatic urethra.

Increased Incidence of Malignancy:

• Uptake associated with a visible lesion or area of focal calcification the CT exam.
• Focal uptake located in the peripheral zone.
• The presence of associated hypermetabolic nodes or bone lesions.

Distant Disease: Most commonly to the bones, lymph nodes, lung, liver and brain.

Indications for PET/CT Imaging:

Screening, Diagnosis & Initial Staging:

• Due to the poor FDG avidity of many prostate cancers, the overlap of increased uptake often associated with prostatitis, the marginal sensitivity of detecting pelvic nodal disease and the limitations created by superimposition of intense bladder activity, PET/CT currently has no role in the screening or diagnosis of prostate cancer.  For similar reasons, it is generally of limited utility for initial staging of the disease.

Utility of PET/CT:

• Detection of local recurrence and/or metastatic disease in patients with “PSA Relapse” or “Biochemical Failure”.
• Monitoring response to androgen deprivation therapy.
• Assessing extent of metabolically active castrate-resistant disease.
• Assessing quiescent versus metabolically active osseous metastatic disease.
• Prognosis assessment.
• Directing re-biopsy (if initial results are negative in the setting of a high clinical suspicion of malignancy).
• MRI is considered a better modality for both initial assessment of extracapsular and seminal vesicle involvement, as well as for evaluation of recurrence in the prostatic bed.

What We Report:  

Size, metabolic activity & location for the primary lesion (if visualized) and representative metastatic lesions. 

• Primary Lesion: Often not identified. When present, usually appears as a focus of intense uptake in the peripheral zone (MRI is superior in the evaluation of the primary lesion).
• Regional Disease: Usually hypermetabolic pelvic lymph nodes.
• Distant Disease: Most commonly to the bones, lymph nodes, lung, liver and brain.

Bone Scan versus PET/CT for Osseous Metastases:

PET/CT imaging has traditionally been considered less sensitive than a conventional bone scan for blastic metastases (e.g. prostate & breast cancers).

Recent literature, however, suggests that while a bone scan may be more sensitive than a PET scan alone for blastic lesions, it may be actually less sensitive when compared to a PET scan plus a CT scan (e.g. a PET/CT scan).

False Positives:

• Benign prostatic hyperplasia
• Prostatitis
• Prostatic urethra (if urine present)

False Negatives:

• Primary and metastatic lesions < 8.0 mm (“beneath the resolution of PET”)

Additional Radiotracers:

Pending further investigation, C-11 Acetate, C-11 Choline, F-18 Choline, C-11 Methionine, F-18 Fluorocholine and F-18 Sodium Fluoride may prove useful in PET/CT prostate imaging.