ASCO GU 2017: The utility of Imaging In challenging Cases with High Risk, Recurrent, and Advanced Prostate Cancer - Radiologist - Session Highlights

Orlando, Florida USA (UroToday.com) Dr. Jeffrey Weinreb from Yale New Haven Hospital is the invited radiology expert to discuss the use of new imaging techniques in patients with high risk, recurrent and advance prostate cancer. The current modalities being used to stage patients with high risk disease (CT scan, MRI and Bone Scan) remain limited at best.

Over the last few years there was been great advancement in the field of nuclear medicine to help with staging of patients with high risk prostate cancer. Several PET radiotracers have been introduced such as C-11 choline, C-11 acetate and F-18 fluorocholine. C-11 choline and C-11 acetate have the advantage of low urinary excretion which improve the detection of low volume metastatic disease in the pelvis. F-18 fluorocholine does have the advantage of a longer half-life (110 min vs. 20 min) which allows the agent to be made in a central facility. Prostate specific membrane antigen (PSMA) PET CT scan has also been re-introduced with very encouraging results. The modified antigen is now a surface antigen which allows for better biding compared to its precursor. PSMA expression has been correlated with early biochemical recurrence, higher tumor stage, higher Gleason grade, and post-operative biochemical failure which makes it an excellent marker for aggressive disease.

Whole body MRI was also been introduced as an improved technique for the identification of bone metastasis. In comparison to the standard bone scans (Tc-99m) MRI allows for detection of signal difference in the bone marrow rather than an indicator for osteogenic activity thus improving the early detection of bone metastasis. Whole body MRI also allows for the detection of adenopathy merging two imaging modalities into one. Most of the data for this imaging technique is from Europe and the technique remains to be validated in the US.

There is excitement in the use of some of these new nuclear imaging techniques for localization of disease in patients who presents with biochemical recurrence following local treatment (radical prostatectomy or radiation treatment). Evangelista and colleagues, performed a meta-analysis on the use C-11 choline and F-18 fluorocholine in the setting of biochemical recurrence. The study showed that sensitivity and specificity for detection of disease was 75% and 82% at the prostatic bed and 100% and 82% in the lymph node, respectively. In a study by Mitchell et al, C-11 choline scans were noted be clinically useful only 32% of the time. On further evaluation of the data the performance of C-11 choline scans improved with higher levels of PSA with 89 % of scans being found to be clinically useful when the PSA was 5 ng/mL vs. 44% when the PSA was < 1 ng/mL, the optimal PSA for lesion detection with C-11 choline scans was found to be 2 ng/mL.

In summary, the advent of these new imaging techniques have allowed for better patient staging and treatment counseling in those presenting with high risk, recurrence or advance disease. Nonetheless, data from all this new imaging modalities remains to be validated in large populations and prospective treatment cohorts.

Presenter: Jeffrey Weinreb, MD, FACR, Yale New Haven Hospital

Written By: Andres F. Correa, Society of Urologic Oncology Fellow, Fox Chase Cancer Center

at the 2017 Genitourinary Cancers Symposium - February 16 - 18, 2017 – Orlando, Florida USA