Axumin for Early Detection of Recurrent Prostate Cancer
It has been possible to detect prostate cancer recurrence for years using the PSA test, but what hasn’t been possible is to detect where the cancer has metastasized until the PSA had risen to 10 or even higher.
Problem of waiting for PSA levels to rise
Waiting for the PSA level to rise creates a problem. As Gerald Andriole, MD, chief of urological surgery at Washington University School of Medicine in St. Louis noted “When PSA rises, where is the specific area of recurrence? Could it be in the area wherein the prostate once resided? Or could it be in the pelvic lymph node? Or in the bones? Or somewhere else?” He goes on to say that conventional bone scans “revealed the area of recurrence when it was too late for [efficacious] treatment.”1
One potential solution
Axumin, a radioactive injection used in conjunction with a PET scan changes this dynamic. The FDA approval press release notes that imaging tests alone cannot determine the location or recurrent prostate cancer at low PSA levels, but that two clinical trial studies found that Axumin could provide accurate images for these patients.2
How Axumin does this sounds surprisingly simple (although I’m sure figuring it out from the scientific side was anything but). Prostate cancer absorbs amino acids more rapidly than regular cells. The radioactive tracer in Axumin links to amino acids, and thus is itself absorbed into the cancer. The radiation glows on the scan, revealing the location of the cancer.3
With which stage of prostate cancer were you last diagnosed?
Identifying local versus systemic recurrence
There are really essentially two types of recurrent prostate cancer. The first is a “local recurrence” where the cancer is still contained to the prostate (if the patient had radiation for their original treatment) or limited to the prostate bed (if the patient had the prostate removed). The second, known as a “systemic recurrence,” is when the cancer metastasizes to other parts of the body, such as the lymph nodes or bones.
Identifying a recurrence when it is still local is optimal and Axumin is increasing the odds on this. In addition, even when a recurrence is systemic, the hope is that it can be identified, isolated, and the treatment targeted before it spreads further.
No test is perfect
Of course, no test is perfect and Axumin can’t predict metastasis 100% of the time. However, if Axumin finds an inconclusive abnormality, it can be combined with another test, such as an MRI for confirmation. This process can work in reverse, with an item spotted on an MRI checked with Axumin to see if something “lights up.”4
Why all of this is important seems pretty self-evident, but let’s let an expert explain it for us. Michael Kipper, MD, a specialist in nuclear medicine at Genesis Healthcare in San Diego states: “Radiation oncologists will tell you that, once you get to a PSA above a certain level, your chance of curing the patient drops. If we can find these things with studies like Axumin and the PSA is at a certain level, we can keep the patient in a category where they can be cured, rather than having them in an area where we are treating and merely prolonging life.”5
Advancing screening technologies
It should also be noted that while Axumin has been approved for locating prostate cancer in recurrence situations, it is easy to imagine future uses. For example, men with an original diagnosis who have a high Gleason score or an extremely high PSA could undergo an Axumin test to determine if the cancer has escaped the prostate. Catching the spread as early as possible could lead to aggressive treatment and, obviously, yield the best possible results for the patient.
The flip side is that patients with a negative Axumin test could be spared unnecessary treatments and the corresponding side effects, in spite of the high PSA or Gleason score. Another use could be for targeting specific treatments. As forms of radiation become extremely precise, they can target previously inaccessible areas without damaging surrounding tissue. Combining these technologies with Axumin scans could allow doctors to locate and better access these targets.6
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