Beyond the Prostate

ProstaScint® Scan

“ProstaScint® Scan is a staging test that utilizes a radioactive isotope, which is attached to a monoclonal antibody (mAb), which targets a specific cancer protein known as prostate specific membrane antigen (PSMA). After this combined isotope-mAb is injected into the bloodstream, it will track down that particular cancer protein and then attaches to it. This is an imaging test rather than a blood test per se. Three to four days after being injected, a patient is scanned with a special camera that picks up the radiation emitted by the isotope and locates the cancer.

If a patient’s PSA is very high, for example, in excess of 20, or if there are other additional factors like a Gleason score of 8 or higher, or an elevated PAP, then a patient should probably undergo a ProstaScint® study. Our institution uses this test for patients whom I suspect are at a high risk for having cancer which has gone beyond the prostate gland. The ProstaScint® studies may lend some important information for these patients because it tells us a great deal about soft tissue. If there is lymph node involvement, a ProstaScint® scan may show the cancer going very accurately and methodically from the prostate gland up to the internal iliac or lymph node chain, or to known sites or banks where prostate cancer commonly goes.

As yet, not many institutions use the ProstaScint® scan although its availability is growing and it is FDA approved. It can be a revealing test, buy again, it should be limited to patients having more aggressive cancer. The medical staff at the center understand that it is associated with false positives and it’s expensive. One of its advantages, however, is that while other test may be affected by a patient being on hormones, the ProstaScint® scan should still be predictably effective because it’s looking for PSMA rather than PSA. Compared to PSA, only relatively small amounts of PSMA are detectable in the bloodstream or prostate cancer patients.

Fusing the ProstaScint® with a helical CT study or MRI significantly improves the predictive accuracy of the ProstaScint® test (fewer false positives and negatives). In patients with Gleason 8 to 10 tumors, a ProstaScint®/CT/PET Fusion may be dictated. Fusion studies are relatively new and are only as good as the technologist performing it and the radiologist interpreting it. Like everything else in this field, it pays to search out experienced practitioners who deal with a large case load.”

Comidex®

“The Comdibex® imaging technique allows us to clearly distinguish between benign and malignant lymph nodes and to construct 3-dimensional maps to guide clinicians. Comdibex® is a non-particle test that utilizes ferrous oxide (Ferumoxtran-10) as a contrast agent. The patient is scanned after infusion. This test is currently awaiting FDA approval, and in the meantime some patients travel to the Netherlands to undergo testing. Fused with MRI, Comidex® has opened up whole new areas that we can treat. In practice, the predictive accuracy approaches 100% and it can pick up metastases as small as 1 millimeter.

Our institution has the ability to integrate the findings from a Comidex® scan into a computerized treatment plan for the patient. Without this, the valuable information collected from this state-of-the-art imaging procedure would not result in an improved targeting of tumors in other parts of the body. For those patients who make the trip to the Netherlands for this procedure, the understanding that once we know where the tumors lie we can target them effectively is very reassuring to someone previously fighting a poorly defined enemy.”