Bone Scans for Metastatic Prostate Cancer

Sanibel, FL; photo BJ Gabrielsen

 

 The most troubling thought for prostate cancer patients whose cancer has recurred after an initial radicalprostatectomy is the fact that there are PSA-producing cells located somewhere in our bodies. While subsequent treatments such as androgen deprivation (hormonal) therapy may keep these cells under control, there are undoubtedly micro-metastases somewhere in our bodies. When the controlling therapies are discontinued, the cells begin to multiply and PSA rises. Bone scans are generally prescribed to identify sites of metastases. The scans involve the injection of a small amount of a radioactive element, technetium-99 (as technetium Tc 99m medronate). Greater than 90% of the mild radiation produced is eliminated from the body in 24 hours. It is generally accepted that technetium Tc 99m medronate is deposited on the surface of hydroxyapatite crystals, a mineral form of calcium, which comprises up to 50% of bone. Rapidly dividing tumor cells require enhanced blood flow (a process called angiogenesis) in order to grow.  Enhanced blood flow and / or blood concentration is most important in the delivery of the technetium-99 reagent to sites of uptake. Therefore, actively dividing cancer cells in bone would be specifically targeted. In addition to areas of abnormal osteogenesis (bone formation) such as those that occur with metastatic bone disease, other non-cancerous conditions such as Paget’s disease, arthritic disease, osteomyelitis (bone infection), and fractures can also be identified in a bone scan. Bone scans may not always be recommended as long as a patient’s PSA levels are not increasing. In my own case, even though my PSA had remained at very low or at undetectable levels, my Johns Hopkins urologist recommended a bone scan since I had not had one in seven years. His rationale was that even though the likelihood of seeing bone metastases is small, nonetheless, the disease can progress on hormonal deprivation therapy even if the PSA is low. Small quiet progression, if it is found, is something to be noted and followed. Thank God, my bone scan showed no evidence of metastatic cancer but it “lit up like a Christmas tree” since it revealed areas of formerly-broken bones (ankle, wrist, ribs) and arthritis in my lower spine and right hip which had been replaced in 1991. Physicians may differ in their prescriptions for bone scans. Therefore this website commentary is for information purposes only and should be utilized only after discussion with your personal health care provider.  Since this blog was initially written, an excellent review article entitled “Imaging Studies for Prostate Cancer: What to Expect” was published in the October 20th, 2011 edition of the Johns Hopkins Prostate Disorders Health Alert. The article goes into more detail about when bone scans should be prescribed, ProstaScint scans for metastases to lymph nodes or small organs and the uses of computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) scans. 

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