Prostate cancer is one of the most common types of cancer in men. In the United Kingdom, over 40,000 new cases are diagnosed every year. According to the American Cancer Association, 1 in 6 men will be diagnosed with prostate cancer in their lifetime, with two-thirds of the cases being diagnosed after the age of 65.
With it being such an important and common problem, it is good to have a good knowledge about this condition and how it can be treated.
Risk factors for prostate cancer
There are a number of risk factors that can lead to prostate cancer, some of which can be modified. Below is a list of the common ones –
1. Age – Prostate cancer is common over the age of 65, and rarely seen under the age of 40.
2. Ethnicity – It appears to be commoner in men of African-American descent.
3. Family History – There are a number of reported cases of prostate cancer running in families, especially amongst siblings or first degree relatives.
4. Genetics – This ties in with family history, with studies showing abnormalities in chromosome 8 being a cause.1 It is likely that genetic factors are responsible for up to 10% of cases of prostate cancer.
5. Dietary factors – While this is not backed by solid evidence, it is likely that prostate cancer can be linked to high intake of dairy products (rich in calcium) and even red meat.
6. Smoking – This is a modifiable risk factor which appears to have a weak link to mortality from prostate cancer.
7. Obesity – This is yet another modifiable risk factor that is linked to development of prostate cancer.
In many patients, it is a combination of all these factors that lead to the development of prostate cancer.
Cause of prostate cancer
Without delving in too deep into a scientific reason for prostate cancer, there are theories that suggest prostate cancer occurs due to mutations in some DNA components. It is also postulated that excess androgen production may be linked to its development.
Patients with prostate cancer can have no symptoms whatsoever for a while, but eventually can develop problems with passing urine (dysuria) or even increased frequency of urination. Patients may wake up at night often to pass urine. However, these symptoms are not specific to prostate cancer and can occur in patients who have an enlarged prostate gland.
If prostate cancer has advanced significantly, patients may complain of blood in the urine (hematuria). Some cases, patients may also suffer an inability to obtain and maintain an erection (erectile dysfunction).
Unfortunately, advanced cases of prostate cancer can spread to the bones, especially the spine, the ribs and the hips, causing significant back pain and occasionally compressing the nerves emerging from the spinal cord. This can constitute a medical emergency requiring prompt treatment.
General examination is usually normal in early stages. A digital rectal examination is always performed to assess the size and the surface of the prostate. This will give the doctor an idea if the prostate is enlarged and if it may be cancerous.
In more advanced cases of prostate cancer, patients may have a tender spine or reduced movement of the hip due to bone involvement.
Investigations for prostate cancer
There are only a few investigations that are performed –
1. Prostate Specific Antigen – This is a simple blood test and is a good marker of prostate involvement in any disease. However, it is not 100% specific to cancer and can be elevated even if the prostate is enlarged. PSA levels are generally mildly elevated if the prostate is enlarged but highly elevated in the presence of cancer.
2. Ultrasound – An ultrasound scan of the prostate can help estimate the size of the prostate and the nature of enlargement. This is usually performed by placing the probe in the rectum (transrectal ultrasound – TRUS)
3. Prostate biopsy – Here a small piece of the prostate is taken and examined under a microscope. Cancer of the prostate gives a characteristic appearance. It helps to stage prostate cancer and estimate prognosis (see table).
4. Bone scan – This is usually performed in advanced cases of prostate cancer to assess the degree of spread to the bones.
Two bone scans showing a number of black hot spots
indicating the sites of spread of prostate cancer.
Stages of prostate cancer – TNM Staging
1. T (Tumor)
- TX – Primary tumor cannot be assessed
- T0 – No evidence of primary tumor
- T1 – Clinically in apparent tumor not palpable or visible by imaging
- T1a – Tumor incidental histologic finding in less than or equal to 5% of tissue resected
- T1b – Tumor incidental histologic finding in greater than 5% of tissue resected
- T1c – Tumor identified by needle biopsy (because of elevated PSA level); tumors found in 1 or both lobes by needle biopsy but not palpable or reliably visible by imaging
- T2 – Tumor confined within prostate
- T2a – Tumor involving less than or equal to half of a lobe
- T2b – Tumor involving more than half of a lobe but not more than 1 lobe
- T2c – Tumor involving both lobes
- T3 – Tumor extending through the prostatic capsule; either no invasion into the prostatic apex or invasion into, but not beyond, the prostatic capsule
- T3a – Extracapsular extension (unilateral or bilateral)
- T3b – Tumor invading seminal vesicle(s)
- T4 – Tumor fixed to or invading adjacent structures other than seminal vesicles (eg, bladder neck, external sphincter, rectum, levator muscles, pelvic wall)
2. N (nodes)
- NX – Regional lymph nodes cannot be assessed
- N0 – No regional lymph node metastasis
- N1 – Metastasis in regional lymph node or nodes
3. M (metastasis)
- PM1c – More than 1 site of metastasis present
- MX – Distant metastasis cannot be assessed
- M0 – No distant metastasis
- M1 – Distant metastasis
- M1a – Nonregional lymph node(s)
- M1b – Bone(s)
- M1c – Other site(s)
Gleason scale to estimate prognosis. Poorly differentiated tumors have a worse prognosis.
1. Active surveillance –This includes a monitoring approach and is considered in early stages of the cancer.
2. Radical prostatectomy – This includes removal of the entire prostate using a surgical approach.
3. Radiation therapy – This is usually reserved for patients who have advanced disease and spread of the cancer.
4. Hormone therapy – This is aimed at suppressing the release of androgenic hormones released by the pituitary. They are offered as oral treatments or injections. Drugs include Flutamide and Goserelin, to name a couple.
Screening for prostate cancer
When patients have problems with their prostate, they usually notice alteration in their urinary stream. Prostate cancer can be detected early by testing for PSA levels. This also forms a useful screening tool to help pick up the clinical condition early.
Unfortunately, the test is not always accurate as levels can be elevated even
if there is mild inflammation of the prostate. This can make early diagnosis of prostate cancer rather difficult. However, an elevated PSA level can result in a subsequent biopsy being performed, which would help diagnose prostate cancer definitively.
Prevention of prostate cancer
It is clear from the discussion previously that there are certain modifiable risk factors such as smoking and weight that can be altered in order to reduce the risk. In other words, stopping smoking, losing weight and diet and exercise are essential components of reducing risk.
Taking a prescription of 5-? reductase drugs such as finasteride has been shown from studies to reduce the risk of prostate cancer.
1. Al Olama AA, Kote-Jarai Z, Giles GG, Guy M, Morrison J, et al. Multiple loci on 8q24 associated with prostate cancer susceptibility. Nat Genet. Oct 2009;41(10):1058-60.