Prostate cancer is the most common cancer and the third leading cause of cancer death in men in Canada. In the past, it was often detected at an advanced stage when it was not curable, and patients often died of the disease. Fortunately, with screening tests such as prostate specific antigen (PSA) and/or the palpation of the prostate by digital rectal examination (DRE), we’ve been able to dramatically reduce the stage at which prostate cancer is usually diagnosed. Now, almost all patients are treated with intent to “cure.” Even with the recent results of two large studies in Europe and the US in March 2009, the value of PSA screening in enhancing patient quality of life and improving survival remains controversial and the subject of much debate.
Men who have been newly diagnosed with prostate cancer need to gather as much information as possible about potential treatment options in order to make an informed decision. This article provides an overview of what you need to know at the start of your journey.
Predicting the risk
Approximately one in three patients who have a biopsy following a suspicious PSA or DRE will be found to have prostate cancer, although the chances also depend on an individual’s risk profile. Patients usually first learn of the diagnosis from their urologist, who will decide if other tests need to be done and will discuss the various treatment options. If radiation is being seriously considered, the patient will be referred to a radiation oncologist. With multiple treatment options now available, it’s essential to assess each individual patient’s risk of disease progression prior to initiating therapy.
The urologist categorizes the risk of cancer having spread beyond the prostate and the probability of being cured with local therapies using a number of critical indicators: PSA, abnormalities felt on DRE, and Gleason score. These factors help us classify patients with clinically localized prostate cancer into low-, intermediate- or high-risk categories.
Low risk (favourable)
PSA less than 10 ng/mL
Stage T1c–T2a: there are no nodules felt on DRE, or a small nodule limited to less than half of one side of the prostate
Gleason score: 6 (3+3)
Intermediate risk
- PSA 10–20 ng/mL
- Stage T2b: nodule is larger but confined to one lobe of the prostate
- Gleason score: 7 (3+4 or 4+3)
High risk
- PSA greater than 20 ng/mL
- Stage T2c: nodule spreads into both lobes of the prostate but is still confined to the prostate
- Gleason score: 8 to 10 (3+5, 4+4, 4+5, 5+4 or 5+5)
More recently, we’ve also recognized that the amount of tumour in the tissue cores taken during the biopsy can predict risk. If several, most or all of the cores contain cancer, the risk is greater than if it’s found in only one or two cores. Similarly, the percentage of each involved core that consists of cancer is an important risk factor.
Predictive tools have been developed based on statistical analysis of the various risk factors in large groups of men with prostate cancer. These mathematical models — nomograms or artificial neural networks — incorporate all the variables and provide percentage risks that an individual will have a specific measurable outcome (e.g. spread of the cancer to the lymph nodes or bone). These tools are very useful, but remember that most are only 70–80% accurate.
Prostate cancer imaging
In most cancers, it’s extremely important to obtain an accurate image of the tumour with radiologic techniques such as computerized tomography (CT). While this would also be advantageous with prostate cancer, we’re currently not able to image the prostate adequately in most cases. The transrectal ultrasound (TRUS) performed at the time of biopsy doesn’t usually give a clear image of the tumour. CT scans are sometimes done in higher-risk patients to assess for enlarged lymph nodes in the pelvis, but they don’t tell us much about the prostate itself. The most promising technology is magnetic resonance imaging (MRI). MRI is useful in some patients with more advanced disease, but is not routinely used in staging. As it continues to be refined, it’s likely that we will use MRI more frequently in the future.
The most frequent imaging study performed for prostate cancer, other than TRUS, is the bone scan. This is done mostly in high-risk patients to assess for possible bone metastasis, but it can’t detect microscopic spread of cancer to bone.
What are your options?
Since the urologist (a surgeon) most often makes the diagnosis of prostate cancer, surgery is often the first treatment option discussed. Radical prostatectomy involves complete removal of the prostate as well as, in intermediate-risk and high-risk patients, the pelvic lymph nodes. It can be performed by traditional open techniques, laparoscopy or with robotic assistance. Most patients will also be considered for radiation therapy. Radiation can be administered in the form of brachytherapy, which involves placing tiny radioactive seeds directly in the prostate, or external beams applied precisely to the prostate from the outside.
Newer therapies include freezing (cryoablation) and heating (HIFU or high intensity focused ultrasound), both performed by a urologist. These methods are both minimally invasive, but neither has been studied adequately to be a recommended option for most patients.
Androgen deprivation therapy, which turns off testosterone production through drugs or removal of the testicles (castration), is used for advanced disease or for patients with high-risk disease who are unable to undergo radiation or surgery.
Active surveillance
While the enhanced detection of prostate cancer with PSA and DRE screening appears to be a success story, especially when coupled with recent treatment advances, it’s not without controversy or uncertainty. The advent of prostate cancer screening has led to quite a different problem — over-detection. There’s a large disparity in the number of men diagnosed with prostate cancer per year (Health Canada estimates approximately 24,700 in 2008) and the number of deaths from the disease (about 4,300 or 17% of diagnosed cases). While we can attribute this partly to the multitude of good therapies we’re able to offer our patients, the more important factor is the slow natural history of most prostate cancers relative to the risk of death from other causes. Many men diagnosed with prostate cancer are unlikely to develop any signs or symptoms in their lifetime, and even fewer are likely to die from the disease. If all diagnosed men are treated, however, we’re subjecting them all to the side effects of treatment, without measurable benefit for all.
It has therefore become very important to balance the risk of the prostate cancer diagnosed with each patient’s overall health status before deciding to treat. Many men with low-risk disease can be closely monitored with PSA, DRE and repeat biopsies, and therapy can be started only if/when signs of disease progression appear (e.g. a rapid rise in PSA or an increase in the Gleason score). The belief is that the cancer can be treated just as well then as at the time of original diagnosis. We call this strategy active surveillance with delayed intervention. Together with their doctors, more and more patients are choosing this management approach, and we continue to refine our ability to predict which patients it’s most suited for.
Dr. Peter Black is a Research Scientist at the Vancouver General Hospital Prostate Centre and Assistant Professor of Urologic Sciences at the University of British Columbia. He specializes in the treatment of urologic cancers.
