The prostate is a small gland that is part of the male genitalia. In an adult man the prostate size is from three to five cm and weighs about 10-20 g. It is located in the pelvis, below the bladder and before rectum. It surrounds the initial portion of the urethra and is covered by muscle tissue and a fibrous capsule. The last part of the intestine, i.e. the rectum, is located in the vicinity of the back portion of the prostate. Near the prostate are localized some lymph nodes , which are part of the lymphatic system.
The prostate is made up of a glandular part, containing many small glands that secrete a whitish liquid rather dense, the prostatic secretions, which mixes with the one coming from the seminal vesicles and with sperm to form the seminal fluid. Among the components of this liquid, there is also a protein called Prostate Specific Antigen or PSA that is present and measurable in the blood, and represents a parameter which, when high, is indicative of a prostate carcinoma. In addition to the glandular part there is also a muscle tissue.
The growth and function of the prostate depend on the male sex hormones, the androgens, which include testosterone, produced by the testes, dehydroepiandrosterone, produced by the adrenal glands, and dihydrotestosterone, produced by the prostate itself.
With the development of body, the prostate gradually increases its size until it reaches the full function around the age of thirty years. Then its volume remains unchanged up to forty, then increases again, slowly, up to 70-80 years.
The prostate gland is subject to inflammatory diseases (prostatitis), benign enlargement (Benign Prostatic Hypertrophy, BPH or Prostatic Adenocarcinoma (Adenomatius) and malignant cancers (Prostatic Adenocarcinoma) and because of its location, these diseases often affect urination, ejaculation or defecation.
Cancers may develop especially in the glandular part and depending on their development may remain confined within the gland itself or escape from it affecting the surrounding organs.
Prostate cancer in Western countries is becoming one of the most common malignancies among males. In fact it represents one of the most commonly diagnosed malignancy, constituting about 10% of all newly diagnosed cancers in man throughout the world. Thanks to the diffusion and improvement of diagnostic methods in the last ten years, the incidence rate of prostate cancer has consistently increased: over the period 1998-2002 was the second most frequently diagnosed cancer in men and mortality recorded a slight trend towards its reduction. Mortality rates for prostate cancer in the world are the following:
In Italy, about 23,000 new cases are diagnosed every year while in 2002 there were more than seven thousand deaths for prostate cancer. Incidence rates vary considerably in our country with the lowest values in the areas of the South, probably due to a different distribution on the national territory of the use of prostate-specific antigen test (PSA). About 75% of new cases of prostate cancer are over the age of 65. However in the last 20-30 years, the incidence has increased significantly in men aged between 50 and 59 years.
Prostate cancer is classified as an adenocarcinoma or glandular cancer, and begins when normal secreting cells undergo mutation. The region of the organ in which the tumor is more common is the peripheral zone. Initially, small groups of cancer cells remain confined locally, a condition known as carcinoma in situ or prostatic intraepithelial neoplasia (PIN). Although there is no proof that PIN is a precursor of adenocarcinoma, however there is a strong correlation. Over time these cells begin to multiply and spread to the surrounding prostate tissue (the stroma). It is possible that the tumor grows enough to invade surrounding organs such as the seminal vesicles or the rectum; cancer cells can also develop the ability to travel through the bloodstream and lymphatic system. The prostatic adenocarcinoma infact is considered a malignant tumor for its potential invasiveness, ie the ability to give rise to metastases, especially in the bone, lymph nodes, rectum and bladder.
A prostate cancer at an early stage usually does not cause symptoms. It is often diagnosed after the detection of an elevated PSA level during a routine check. Sometimes, however, the cancer cause some problem, often similar to those involved in Benign Prostatic Hypertrophy, such as pollakiuria, nocturia, difficulty in initiating urination and to maintain a constant flow, hematuria, stranguria. It can also cause problems in sexual function, such as difficulty in achieving an erection, and painful ejaculation. At the latter stage can cause additional symptoms when it spreads to other areas of the body. The most common symptom is bone pain, often localized to the vertebrae, pelvis or ribs, caused by metastases in these sites. The spine localization can cause compression of the spinal cord, causing leg weakness and urinary and fecal incontinence.
The causal factors of prostate cancer are still unknown although in recent years important achievements have been achieved in the molecular research.
It is believed, however, that there are many contributing factors or risk factors that interact to develop the disease. Among the risk factors for the development of prostate cancer , the most recognized are definitely genetics, age, race, diet, lifestyle and taking medication.
The genetic of a man contributes to the risk of developing this cancer, since it has been observed an increased incidence in certain racial groups, in identical twins, and in men carriers of certain genes, responsible for approximately of a 9% of the onset of prostate cancers. Infact it is estimated that the presence of a first-degree relative affected with prostate cancer increases the risk of 2 to 3 times. Two or more first degree relatives of parents increases the risk from 5 to 11 times. These associations between familiarity and prostate cancer indicate the role of genetic factors in the onset of cancer. However it was not yet identified a well-defined area or chromosomal gene responsible for these inherited forms of prostate cancer. Indeed, many different genes are suspected, including the BRCA1 and BRCA2 genes, which are also implicated in the development of ovarian cancer and breast cancer.
The incidence of prostate cancer increases progressively with age, it is rare in men under 45 years old, but it becomes more frequency with advancing age. In fact, the average age of diagnosis is 70 years , so much so that 50 % of the cases has clashed in subjects older than 70 years.
In the United States, prostate cancer more commonly affects black men than whites or Hispanics, and in the first also causes more deaths. Then the risk is so high in African-Americans and is reduced in populations of the Far East.
The dietary intake of some foods, vitamins and minerals can contribute to the onset of the disease. Men with higher serum levels of linolenic acid, a polyunsaturated short-chain fatty acid, have a greater risk to develop prostate cancer. However, the same studies have shown that high levels of long-chain fatty acids (EPA and DHA) decrease the incidence. Other dietary factors that can increase risk include low intake of vitamin E (found in vegetable oils), lycopene (found in tomatoes), omega-3 fatty acids (found in fatty meat in fish such as salmon) and selenium. Even low blood levels of vitamin D may increase the risk of developing cancer; this may be related to less exposure to sunlight. Then the western countries diets, with a high energy value, rich in protein, calcium and animal fats favor the development of this cancer.
Taking some drugs, some medical conditions and hormonal changes are risk factors. For example, the constant use of nonsteroidal anti-inflammatory drugs (NSAIDs), and probably also the lipid-lowering drugs, such as statins, can reduce the risk. More frequent ejaculations may lower the risk: in fact, a recent study showed that men who ejaculate five times a week, from twenty to thirty years of age, reduce the risk of developing this cancer. Infection or inflammation of the prostate (prostatitis) may increase the probability of developing this cancer. In particular, sexually transmitted infections such as chlamydia, gonorrhea and syphilis appear to increase the risk, as well as obesity and elevated blood levels of testosterone and male sex hormones, which produce a hyper-stimulation of the prostate gland.
Of course the primary objective of prevention of prostate cancer is the prostate annual check-up and then from early diagnosis to identify cancer at a stage in which does not cause urinary symptoms, it is confined to the gland and the results of surgical treatment, hormonal, radiotherapy are very favorable: in fact, the median survival exceeds, in these cases, the 15 years. This type of prevention can greatly affect the course of the disease and allows in some cases even complete recovery from the disease. At the moment, however, without any early prevention programs, the diagnosis is often delayed and in most of the patients came to the diagnosis, the cancer has an extracapsular extension, or is already in the metastatic phase. In these cases, the prognosis is poor and the survival is approximately 30 months or less.
Another way to intervene is represented by the modification of the known risk factors, in order to greatly reduce the risk of onset of prostate carcinoma. Thus, a proper lifestyle, diets low in animal fats and rich in phytoestrogens, fruit, vegetables and lycopene, some vitamins (such as vitamin E) and selenium can help to reduce the risk of developing prostate cancer.