It would be useful if one could detect and identify the location of localized prostate cancer recurrences and metastatic disease in early PSA recurrence in men who had previously failed initial cancer treatments. For example, such identified “focal” or local recurrences in 1-2 specific areas of the body could then be treated surgically or with targeted radiation. These areas of recurrence might not have been detectable by bone, CT or other scanning methods alone. Physicians at the Mayo Clinic in Rochester, Minnesota and at the Arizona Molecular Imaging Center in Phoenix, Arizona describe the use of positron emission tomography (PET)/CT scanning to identify such localized areas of recurrent prostate cancer in men who have failed surgery, radiation, hormonal and/or chemotherapies. The specific tumor-targeting agents are C-11 choline and C-11 acetate administered intravenously. These radioactive agents emit positrons (positively-charged electrons) over a short period of time; their half-life is about 20 minutes. Therefore, the agents have to be prepared in an on-site cyclotron just prior to their use. In preliminary results reported in the August, 2012 issue of the Prostate Cancer Research Institute (PCRI)Insights, Arizona researchers report an overall detection rate of 85% for recurrent or metastatic disease using C-11 acetate PET/CT imaging. Detection was followed by radiation therapy or surgical removal of the identified lesion. Access to C-11 acetate requires participation in an approved clinical study. For information about participating in this on-going Phase II clinical trial see the ClinicalTrials.gov website at http://clinicaltrials.gov/ct2/show/record/NCT01304485. The C-11 choline agent available at the Mayo Clinic has already been approved by the Food and Drug Administration (FDA) as an agent for prostate cancer imaging. It has demonstrated accuracy in detecting lesions in both bone and lymph nodes. Examples of its usefulness are provided in a 17-minute video presentation given by Mayo’s principal investigator, Dr. Eugene Kwon. Both of these studies are relatively small in scope. The usefulness of this technique rests on its ability to identify the specific location of localized cancer recurrences and then the ability to treat them surgically or with radiation. The PET/CT imaging therapy described above would not be applicable to systemic disease covering multiple areas of the body. Its value would be in cases where recurrent tumors / metastases could be identified and localized in a specific area of the body which would allow the tumors to be removed surgically or with radiation.
While PET/CT imaging is not currently widely accessible, it may be very useful in specific cases. On a personal note, I know of a prostate cancer patient who might well have benefitted from the techniques described above. He had undergone a seemingly-successful radical prostatectomy. His PSA remained undetectable for about eight (8) years. Shortly thereafter, he began to experience a strong pain in his lower back / spinal area. X-rays, bone and CT scans were inconclusive in determining the origin of his pain. Meanwhile, his PSA escalated very rapidly to 25 ng/dL. An MRI revealed a mass in his lower back/spine which was removed surgically within two days of diagnosis. The patient’s PSA has been undetectable for the last two years.
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