Prostrate cancer is the result of the presence of a tumour in the prostrate gland which gives rise to urination problems (prostatitis). The tumour may be benign, non-lethal, or malignant, which indicates a lethal, fast growing, spreading cancer. Prostatitis - in itself - is not always a sign of prostate cancer, unless it has ‘metastatised’ to the bones.
Bone scans are a definitive test in the diagnosis of prostrate cancer. A bone scan is a test that detects damage to the bone, including damage that cancer can cause to them. The scan looks at the entire skeleton and looks similar to an x-ray.
The test of bone scan for prostate cancer diagnosis commences with an intravenous injection into the arm by a radioactive tracer. The radioactivity is in the form of gamma rays that spread through the entire body and are gradually absorbed by the bones within a few hours. Then a camera - sensitive to these rays - photographs the entire body. Areas on the skeleton that have had an increased growth or breakdown of bone absorb more of the tracer material than normal bone, and appear as “hot spots” in the images. They are indicators of cancer, fracture, infection, certain types of arthritis, and other chronic bone diseases.
Other areas may not absorb any of the tracers. These appear as “cold spots” and are also considered abnormal. They are less common, and indicate certain types of cancer (multiple myeloma) and certain unhealthy metabolic bone conditions.
While bone scans are certainly useful in the diagnosis for prostate cancer, it has the drawback that it is not an early detection method, as it takes about four to five years before the cancer metastaises.
The National Cancer Institute of USA looks at survival rates in three categories: local, regional and distant. Nearly 90 per cent of prostate cancers are found in the local stage, i.e., where the cancer has not spread beyond the prostate. The five year survival rate for local stage prostate cancer is 100 per cent in the US. If the cancer has spread to nearby areas, it is called regional stage prostate cancer and the survival rate is also 100 per cent after five years. Distant stage cancers are those that have spread to areas such as the lymph nodes, bone or other organs, and a five- year survival rate is only 31 per cent.
In most cases, bone scans are a useful tool in the diagnosis of prostate cancer. To summarise:
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