In 2009, about 192,280 new cases of prostate cancer will be diagnosed in the United States, according to the American Cancer Society (ACS). Prostate cancer is the second most common cancer in males after skin cancer and is the second death-causing cancer after lung cancer. It accounts for about 10% of cancer-related mortalities in men. On the other hand, the prognosis for prostate cancer is quite good. This is because prostate cancer is usually a slow-growing disease and many of those diagnosed do not develop symptoms.
According to ACS about 1 man in 6 will be diagnosed with prostate cancer during his lifetime, but only 1 man in 35 will die of it. and for all men with prostate cancer, the relative 5-year survival rate is nearly 100% and the relative 10-year survival rate is 93%. The 15-year relative survival rate is 79%.
Currently worldwide prostate cancer screening is still dependant on the PSA blood test and the Digital rectal exam.
1) The PSA blood test remains the state-of-the-art screening method for prostate cancer. PSA stands for Prostate-Specific Antigen. It is a substance naturally occurring in the male semen but can also occur in small amounts in the blood. A normal PSA blood level is about 4 nanograms per milliliter (ng/mL). Elevated levels of PSA in the blood can indicate an increase in the number of cancerous cells. However, it may not, hence the reason the PSA test remains controversial.
(2) The Digital rectal exam (DRE) is performed by inserting a lubricated gloved finger into the rectum of the patient to feel for bumps and other abnormalities that might be indicative of cancer. This is possible because the prostate gland is just right in front of the rectum. However, some patients may consider a rectal exam uncomfortable and invasive. It is also less sensitive than PSA.
Unfortunately making an initial accurate diagnosis of prostate cancer is not easy due to the nature of the disease and the limitations of current screening methods.
(1) The ACS states that neither the PSA test nor the DRE is 100% accurate. Abnormal results of these tests don’t always mean that cancer is present, and normal results don’t always mean that there is no cancer. According to the ACS “uncertain or false test results could cause confusion and anxiety. Some men might have a prostate biopsy (which carries its own small risks, along with discomfort) when cancer is not present, while others might get a false sense of security from normal test results when cancer is actually present”.
(2) Furthermore to confound things, several factors and conditions can affect the PSA levels including; Benign prostatic hyperplasia (BPH) – a non-cancerous enlargement that occurs with age can increase PSA levels, Age – PSA levels will also normally go up slowly as you get older, Prostatitis – an infection or inflammation of the prostate gland can elevate PSA levels, Ejaculation can cause the PSA to go up for a short time, and then go down again, medications including herbal mixtures can interfere with PSA measurements and Obesity tends to have lower PSA levels.
(3) In early 2009, two large-scale studies on the risks and benefits of PSA testing were published in the New England Journal of Medicine. Unfortunately, instead of settling the PSA question once and for all, the two studies actually produced somewhat contradictory results.
In the American study on PSA, researchers followed up 76,693 men for 7 to 10 years who either had a PSA test or a DRE and compared mortalities due to prostate cancer. The study results showed that “the rate of death from prostate cancer was very low and did not differ significantly between the two study groups.”
In the European study on PSA, researchers followed up about 182,000 men who either had PSA or no PSA testing and compared mortality rates. The study results showed that “PSA-based screening reduced the rate of death from prostate cancer by 20% but was associated with a high risk of overdiagnosis.
Although the screening tests can detect early cancer they cannot determine whether the cancer will prove to be fast-growing and aggressive or slow growing and benign. For patients and health care providers alike, this lack of clarity in the tests results creates a dilemma: treat the cancer before it spreads any further or do nothing but practice what is called “watchful waiting” or “expectant management” with serial PSAs and eventual biopsy. As a result of the PSA test’s shortcomings there tends to be overdiagnosis which creates overtreatment – too many invasive biopsies and serial blood tests which consumes precious healthcare resources and productivity.
Other screening tests have been developed but due to limitations have not replaced the conventional screening tests.
(1) Transrectal ultrasound (TRUS) uses ultrasound technology to view the prostate gland by inserting a small electronic probe into the rectum. However, TRUS is usually not used as a routine screening test for prostate cancer because its low detection power may not reveal early stage cancer. However, TRUS is a useful method used in conjunction with a prostate biopsy. It helps guide the biopsy needle into the right area of the prostate.
(2) Urine test for prostate cancer. A recent study identified a molecule in the urine that could be used as a disease marker in prostate cancer patients. The molecule has been identified as sarcosine “a derivative of the amino acid glycine. However, the technique is still used primarily for the staging of prostate cancer.
And to add insult to injury if supported by a positive biopsy, chances are that doctors will recommend treatment which usually involves surgical removal of the gland, the so-called prostatectomy. Unfortunately, this conventional and invasive treatment can have the following side effects: interference with sexual and urinary function, psychological distress and lower quality of life.
However, on the bright side, while we wait for better screening methods for prostate cancer, several new treatment trends have emerged.
(1) Interventional cryoablation. Cryoablation is the male equivalent of a lumpectomy, as in breast cancer, which entails localizing the tumor and destroying it by freezing. Interventional radiologists insert a probe through the skin, using imaging to guide the needle to the tumor; the probe then circulates extremely cold gas to freeze and destroy the cancerous tissue. This minimally invasive treatment targets only the cancer itself, sparing healthy tissue in and around the prostate gland rather than destroying it, as traditional approaches do.
(2) Cancer vaccines. These biological response modifiers work by stimulating or restoring the immune system’s ability to fight infections and disease. There are two broad types of cancer vaccines, preventive vaccines, which are intended to prevent cancer from developing in healthy people and treatment vaccines, which are intended to treat already existing cancers by strengthening the body’s natural defenses against cancer. Currently, no cancer vaccine has been approved for prostate cancer but there are several drugs in development.
Researchers at the Roger Williams Medical Center in Providence, Rhode Island are developing “designer immune cells” to treat prostate cancer. They removed T-cells from patients and genetically engineered them to recognize prostate-specific membrane antigen, or PSMA which are found on the outer membrane of prostate cells. The biological drug is currently in Phase I trials.
The therapeutic vaccine Provenge, manufactured by Dendreon, is showing a lot of promise. The recent results from a Phase III trial showed that men with advanced prostate cancer lived an average of 4 months longer than men who did not receive it. However, while the drug prolonged life span of the patients, it does not slow down disease progression.
Another vaccine is PROSTVAC-VF which is made from a virus that has been genetically modified to contain prostate-specific antigen (PSA). The patient’s immune system should respond to the virus and begin to recognize and destroy cancer cells containing PSA.
Of interest one of the largest studies on the effect of vitamin supplements on prostate cancer produced rather disappointing results and had to be stopped prematurely. The National Cancer Institute SELECT trial investigated whether supplementation with vitamin E, selenium, or a combination of the two can lower the risk of prostate cancer. Unfortunately, the results after five years revealed otherwise. In fact, study participants who took only vitamin E actually had a slightly increased risk of developing prostate cancer while those taking only selenium seemed to have a slightly increased risk of developing diabetes.
Currently, no major scientific or medical organization, including the American Cancer Society (ACS), American Urological Association (AUA), US Preventive Services Task Force (USPSTF), American College of Physicians (ACP), National Cancer Institute (NCI), American Academy of Family Physicians (AAFP), and American College of Preventive Medicine (ACPM) support routine screening for prostate cancer.
However, the PSA test still remains the gold standard for prostate cancer screening and on the bright side, PSA test unreliability has and is stimulating the quest for better management techniques, especially in the non-invasive arena. Healthcare providers should openly talk with their patients about the benefits, risks, and uncertainties of prostate cancer screening so that men can “weigh their options” and make “informed decisions” about this issue.
In the meantime, prostate cancer screening continues to need a massage!
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