Like many other cancers, prostate cancer is initially a localized disease. With time, cancer cells gradually spread to the rest of the body. Distant sites are called metastases. For a long time, these metastases retain the same properties as the initial tumour, especially in terms of PSA secretion.
Cancer cells are transported passively by the blood or lymph.
Metastases can therefore be schematically considered to be equivalent to small fragments of prostatic tumour released from the prostate, which subsequently attach to distant sites to form other prostatic tumours with the same characteristics.
The organs most frequently affected by metastases from prostate cancer are bone and lymph nodes of the abdomen and pelvis. Other sites (liver, lungs, brain) are much less frequently involved.
Clinical symptoms and signs of metastases are related to their sites. Bone metastases can induce pain, which is often vague and variable in the beginning and which subsequently becomes more clearly localised.
Lymph node metastases gradually enlarge and induce pain or obstruction as a result of compression, leading to swelling of the ankles (oedema), difficulties urinating, or even constipation.
Metastases are demonstrated and visualised by bone scan for the skeleton and abdominopelvic CT scan for lymph nodes. MRI (magnetic resonance imaging) is a new technique, still under evaluation in this area, which does not appear to provide any additional information compared to CT. PSA (prostatic specific antigen), assayed in the blood, is a useful indicator. It is now generally accepted that a PSA level of 100 ng/ml or more is associated with metastases, while a value less than 10 ng/ml corresponds to a localised tumour.
The treatment of metastatic prostate cancer is based on the fact that prostate cells need androgen hormones to survive. Prostate cancer cells retain this property for a long time, and the objective of treatment is to suppress the secretion of these hormones in order to eliminate a maximum of tumour cells.
More than 70% of these hormones are synthesised by the testes (testosterone), while the rest is secreted by the adrenal glands.
The basis of the treatment of metastatic prostate cancer is therefore castration, which may be either surgical or chemical, in order to obtain maximal reduction of the levels of male hormones in the blood and in organs sensitive to their action, such as the prostate and metastatic cells.
Bilateral pulpectomy or orchidectomy (surgical operations on the testes) was the first alternative proposed in 1941, with an excellent therapeutic result.
LHRH analogues, by blocking the secretion of a gland in the brain (hypothalamus), achieves this reduction of the plasma testosterone level, by means of intramuscular or subcutaneous injections, which are regularly repeated in order to maintain the effect.
Peripheral antiandrogens (peripheral receptor blocking effect) can be combined with LHRH analogues, or can be used alone in tablet form during the day, under certain conditions.
The adverse effects of these so-called "endocrine" treatments essentially consist of hot flushes and loss of libido (sexual desire and erection), except when antiandrogens are used alone in certain patients.
Cytotoxic chemotherapy may be indicated in the context of protocols designed to evaluate its efficacy.
Even metastatic prostate cancer is a disease which can be effectively treated by means of attentive surveillance, and regular and successive treatment modifications, allowing good long-term control of the proliferative process.
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