Prostate cancer is currently the fastest rising cancer in men in Singapore with a 5.6% increase annually. It has risen from being the 6th to the 4th commonest cancer in men in Singapore. Its incidence has increased from out of the top ten tumors in the seventies to 7.6 per 100000 in the early eighties doubling to 14.4 per 100000 in the nineties and 18.4 per 100000 in the new millineum.
The Prostate Gland
The prostate is a walnut-sized gland located between the bladder and the penis and in front of the rectum. The urethra, the tube which carries urine from the bladder and out of the body through the penis, passes through the center of the prostate. The prostate is not a vital organ; however the microscopic nerves that control erection are attached to both sides of the prostate can be damaged as a result of the disease and its treatment.
The primary function of the prostate is the production of a milky substance that nourishes the sperm. Semen is a mixture of seminal fluid and sperm that is ejaculated during orgasm.
Causes & Risk Factors of Prostate Cancer
The major known risk factors for prostate cancer are age, race and family history. Other factors include diet, obesity and the male hormone.
Age is the single most important risk factor in prostate cancer. Most cancers occur in men above fifty years of age and rarely occur in those below forty years. It peaks at the age of seventy years and is thought to be due to genetic mutations that have been linked to development of cancer occuring gradually over time. Age specific rates increase from 5.6 per 100000 at 55 years to 182.3 per 100000 at 70 years and 356.4 per 100000 at 80 years.
African-American men are at the highest risk of developing prostate cancer. They are 65% more likely to develop prostate cancer than Caucasian-American men and they appear to get more severe forms of prostate cancer. Asian men living in Asia have the lowest incidence; however, their prostate cancer risk appears to be on the rise with a rising socioeconomic status. It is interesting to note the increasing incidence of prostate cancer from China to Hong Kong to Singapore to California and to Hawaii. While genetics may play a role, diet is suspected to be a major factor in these racial differences.
One quarter of men with prostate cancer have a history of the disease within their family although only 9% of all prostate cancers are purely hereditary. The risk of prostate cancer doubles among men having a first-degree relative with the disease. With two close relatives, a man's risk increases fivefold, and with three or more close relatives , the risk for developing prostate cancer is alarmingly high – close to 100%.
Diet, Obesity & Nutrition
Diet and weight play a role in the development of prostate cancer. High intake of animal fats, especially those that are charred , are associated with higher rates of prostate cancer. It is still unclear how this can happen although research has suggested that men with the highest levels of the omega-3 fatty acid ALA (alpha-linolenic acid) in their bloodstreams were three times as likely to develop prostate cancer compared to those with low ALA levels. A primary source of ALA was animal and dairy products, particularly red meat. However consumption of two other omega-3 fatty acids found mostly in fatty fish DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), was associated with a lower risk of developing advanced prostate cancer. It was suggested that eating the equivalent of 3 servings of fish per week can reduce cut the risk of developing advanced prostate cancer in half. These benefits did not however extend to those men who were taking fish oil supplements. Charring that occurs with barbecueing meat has also been implicated in causing prostate cancer. One of the heterocyclic amines, which are known human carcinogens, called PhIP, is found in high levels in grilled beef, pork, chicken, lamb, and fish. It is found in higher levels when there is greater charring of the barbecued meat. Vegetables such as broccoli or brussel sprouts appear to reduce PhIP in the body. In one study, examination of the urine of volunteers consuming barbecued red meat followed by broccoli showed an increase in the amount of PhIP excreted, indicating that the vegetables may help to clear the carcinogen PhIP from the body.
Men who are obese and gain a lot of weight early in life have a higher risk of getting prostate cancer and have poorer outcomes compared to those who are not obese or those who gain weight later in life. Nutrition may play an important role in the prevention of prostate cancer. Fruits and vegetables, especially cooked tomatoes, contain key sources of cancer-fighting agents, such as lycopene, antioxidants and fiber.
Vitamin D & Sunlight
Vitamin D is another nutritional factor in preventing prostate cancer. It is found in milk, fish and can be created when skin is exposed to sunlight. Studies have shown that people living in regions that get less sunlight have higher rates of prostate cancer. People with dark skin absorb less sunlight and are known to have lower levels of vitamin D. This may also help to explain some of the racial differences in the incidence of prostate cancer.
Prostate cancer cell growth requires the presence of testosterone. Hence, one of the most common treatments for prostate cancer, is the use of complete suppression of testosterone production to inhibit prostate cancer growth. It is also known that men who were castrated before puberty rarely develop prostate cancer. However, it is still not known whether testosterone actually causes prostate cancer or is just a facilitator of it.
Factors not known to increase the risk of prostate cancer
These include benign prostate enlargement which occurs in a different part of the prostate gland compared to prostate cancer. A larger prostate gland does not increase the risk of prostate cancer but most urologist use the opportunity to screen for prostate cancer in those with urinary symptoms. Cigarette smoking , although a risk factor for many other cancers, does not appear to be a cause of prostate cancer. High sexual activity although rumored on the groun, is also not a cause of prostate cancer. Some studies may suggest a protective effect. Prostate infections and vasectomies have also been found not to be involved in the causation of prostate cancer.
Symptoms of Prostate Cancer
Prostate cancer in the early stages usually has no symptoms. It is often discovered in patients who present with urinary difficulties and are subsequently screened and found to have prostate cancer. In some cases if the prostate cancer is large, lower urinary symptoms of weak urine flow, waking up at night to void frequently, difficulty in starting or holding ones urine, blood in the urine or semen may occur. Symptoms of prostate cancer spread include bone pain in the spine , pelvis , ribs or large bones. Loss of appetite, weight or anemia and generalized feelings of malaise and tiredness are also non-specified symptoms of advanced prostate cancer.
Prostate Cancer Detection & Screening
Prostate cancer is usually diagnosed or excluded with a 1. blood test for total prostate specific antigen(TPSA) and a 2. digital rectal examination of prostate(DRE) by a doctor. We take a level of PSA < 4ng/ml as normal for those above fifty years of age and PSA<2.5ng/ml for those between forty or fifty years of age. The DRE is used to detect any nodules or irregularities in the consistency of the prostate.
At the present moment general mass screening of whole populations is not recommended. What is suggested by most urological associations is to do an annual PSA and DRE from 40 years of age for those with a family history of prostate cancer and from 50 years of age if you have no family history of prostate cancer. As prostate cancer tends to be a slow ly progressing tumor and more men die with their prostate cancer than from it, it is not necessary to screen for prostate cancer if you are above the age of 80years or if your life expectancy is less than 10 years.
Prostate Cancer Stages
Prostate cancer has four distinct stages. These are
- Early or localized prostate cancer where the cancer is localized within the capsule of the gland. The PSA level is usually less than 10 ng/ml in this stage.
- Recurrent prostate cancer where there is a recurrent rise in PSA but no spread to the bones or lungs.
- Metastatic prostate cancer occurs when it spreads beyond the prostate capsule and typically goes to the bones and lungs. Hormone refractory disease, in which prostate cancer continues to grow despite the suppression of the male hormones used in the treatment of metastatic disease.
During the process of diagnosing prostate cancer, a variety of tests and procedures will be done to determine whether the cancer is contained within the prostate or if it has spread to other parts of the body. One can never be totally certain that prostate cancer cells have not escaped from the prostate and lodged in other parts of the body. So despite all the negative results, there is still small risk of missing the tumor spread.
The best-case scenario if one is to have a prostate cancer is to have it detected when the prostate cancer is caught early in the disease process and contained within the capsule of the prostate gland. This allows a potential for a complete cure. Treatment includes surgery to remove the prostate completely either through open surgery or recently , with the use of robots through keyhole surgical techniques. The other alternative is radiotherapy which with new machines and techniques have reduced complications significantly. However long term complications of erectile dysfunction and urinary incontinence do occur with both types of treatments and you would need to discuss the pros and cons of both treatments with your urologist.
When prostate cancer has spread outside the prostate and is growing in other parts of the body, a man is considered to have advanced or metastatic cancer. These can occurs at time of diagnosis or if local therapy has failed. Treatment is started early when there is evidence to suggest disease progression or if symptoms develop. It usually uses hormone suppression in the form of oral medication, 3 monthly injections or surgical removal of the testes to control progression of the disease and the tumor can be seen to shrink in size and disappear on the xrays and bone scans but unfortunately they do not disappear completely and small numbers of hormone refractory prostate cancer cells do remain to recur at a later stage. Hormone therapy however does offer good symptoms and disease control for at least 2 years or more.
Hormone Refractory Prostate Cancer
When the advanced prostate cancer escapes hormonal control, options of hormonal manipulation can be used initially, if not then chemotherapy can be used to control symptoms and help contain the disease for a time. It is however , as in metastatic prostate cancer, not a cure but a method of alleviating and controlling symptoms and disease progression. No treatment is necessary if the patient is asymptomatic. Localised radiotherapy can be used to treat localized bone pain. It is used with much lower doses than that used for curative treatment.
Over the years, many other treatment alternatives have surfaced. Some are promising , others not so good. Treatments using radioactive seeds, cryotherapy(freeze the tumor) and high frequency ultrasound are under investigation and may be considered.
No treatment is good treatment for those with less than 10 years life expectancy as prostate cancer grows slowly most times. So discuss with your urologist if you are more than 75 years of age.So there is no “one size fits all treatment” , like in most other fields of medicine in this day and age. Each treatment should be tailored for each individual not unlike a golf swing. It may be reassuring to know that 86% of all prostate cancers are diagnosed in the local and regional stages and that the 5-year relative survival rate for men whose prostate cancer is diagnosed at this early stage is nearly 100%. Additionally, according to the most recent data, the relative 10-year survival rate is 86%, and the 15-year survival rate is 56%. At this time, it is virtually impossible to know how rapidly or slowly a particular man’s prostate cancer will grow – because at the time of diagnosis it is not known how long the prostate cancer cells have been developing. If the cancer has been found to be contained within the prostate, it could take years for a tumor to double in size. In fact, the cancer might stay within the confines of the prostate indefinitely and never cause problems. Alternatively, the cancer might be growing very rapidly and might spread to other parts of the body quickly. The grade of the tumor , according to a 10 point gleason rating, does have a significant impact on cancer survival. The lower the score the less aggressive the tumor and consequently increased survival.
As prostate cancer is the fastest rising cancer in men in Singapore one should speak with your doctor immediately if you have experienced any of the above symptoms or if you are a man over 50 who has not had a recent prostate cancer screening. If you have a family history of prostate cancer, you should consider screening at age 40.
Even if cancer is found, results of early treatment for localized prostate cancer are excellent. For advanced prostate cancer, hormone suppression therapy has excellent response and is also easy to administer and new chemotherapeutic regimes are available for those that escape hormonal control.
As in all of medicine, prevention is better than cure. So to reduce your risk of prostate cancer eat fewer red meats and high-fat dairy products, eat five or more servings of vegetables and fruits each day, exercise regularly and maintain a normal weight. Some studies do suggest taking Vitamin E with selenium regularly and even drinking red wine and eating tomatoes may have a positive effect. I would go with the red wine and salsa anytime.