The term “cancer” refers to a condition in which cells accumulate uncontrollably—the ability to regulate cell growth or death is lost. So instead of dying as they should, prostate cancer cells live longer than normal cells and form masses of abnormal cells known as tumors. Primary tumors are the original tumors; secondary tumors occur if the original cancer spreads to other locations.
In most cases, prostate cancer is relatively slow-growing, which means that it typically takes a number of years to become large enough to be detectable, and even longer to spread beyond the prostate.
A small percentage of men experience more rapidly growing, aggressive forms of prostate cancer. It’s difficult to know for sure which prostate cancers will grow slowly and which will grow aggressively. This uncertainty can complicate treatment decisions.
Prostate Cancer Is Extremely Common
In fact, it’s the most common non-skin cancer in America, affecting 1 in 9 men.
- Nearly 4 million U.S. men are currently living with prostate cancer, according to estimates.
- One new case of prostate cancer occurs every 3.2 minutes; one death occurs every 17.9 minutes.
- A non-smoking man is more likely to develop prostate cancer than he is to develop colon, bladder, melanoma, lymphoma, and kidney cancers combined.
Studies have shown that the majority of men over 70 have some form of prostate cancer.
To decide what the risk is for a given prostate cancer, doctors will consider several factors, including:
- The grade of the cancer (called the Gleason score—see below)
- The PSA level (including the rate of rise of the PSA)
- The stage of the cancer (how large the cancer is and how far it has spread)
- There are also emerging biomarkers that aid the physician in tailoring treatment for each individual.
By categorizing cancers, doctors can provide an estimate of prognosis and success with various treatment options, which may include little to no treatment. For example, men with low-risk cancers (small volume, early stage, low Gleason, low PSA tumors) have a very high cure rate, nearly 91%. At this stage, the disease is often curable with standard interventions, such as surgery or radiation therapy that aims to remove or kill all cancerous cells.
The Gleason Score
The Gleason score remains one of the best methods for determining the aggressiveness of prostate cancer. It’s actually a sum of two scores—each ranging between 1 and 5—provided by a pathologist who examines the cancer under the microscope.
A Gleason sum ranges from 2-10: 2 being basically like a normal prostate, and 10 looking extremely aggressive. Most men will have a Gleason sum of 6-7 at diagnosis.
Prostate-specific antigen, or PSA, is a protein made by both normal and cancerous prostate cells. PSA can be elevated in cases of BPH, prostatitis, or prostate cancer. There is no absolute cut-off as to what PSA level is worrisome for cancer, and therefore treatment decisions are not based on PSA testing alone. Once the diagnosis of prostate cancer is confirmed by biopsy (removal of pieces of the prostate to look at under the microscope), PSA levels are used to classify tumors into low, intermediate, or high-risk of recurrence. A PSA level of less than 10 is considered low risk, PSA 10-20 intermediate risk, and PSA >20 high risk. Further treatment decisions are made based on these risk classifications.
There are emerging biomarkers that further aid the physician in stratifying prostate cancer into the lower or higher risk categories, and can help inform the decision to undergo treatment or to monitor the cancer. These tests themselves are not 100% accurate, but when added to the total picture of PSA, Gleason score, age and your preferences, can help to tailor the best course of action for your prostate cancer. Tests such as the Prostate Health Index (PHI), 4K Score, PCA3 are now available to aid in this process.
The use of MRI is also an emerging tool that helps us detect tumors in the prostate. The latest studies have shown that tumors that are detected by MRI are more likely to be of intermediate or high risk variety, which helps us find a tumor that is more likely to need treatment. Detecting a lesion with MRI also provides a target for a more specific biopsy of a potentially cancerous lesion, called MRI-Fusion biopsy. MRI, however, is not 100% accurate as it can miss up to 20% of aggressive tumors. In other words, even if the MRI is negative, it can miss an aggressive tumor 20% of the time.
Stages of Cancer
The stage of a cancer is based on how large the cancer is and how much it has spread. Stages are typically expressed as a T score, N score, and M score.
- The T score can range from 1-4, depending on whether the cancer is very tiny and picked up only by PSA testing (score of 1) or whether it is invading other organs (score of 4)
- The N score is 0 or 1, depending on whether the cancer has spread to lymph nodes (bean-shaped organs clustered throughout the body that are part of the body’s immune system) .
- The M score is 0 or 1, depending on whether the cancer has spread outside the prostate to other parts of the body, such as bones or lungs.
It is also important to know how much cancer (in area or volume) was found (either on a biopsy or after the prostate is removed). This information can help guide about whether further therapy should be considered.
Metastatic Prostate Cancer
If untreated and allowed to grow, some cancerous prostate cells can spread outside of the prostate in a process called metastasis. During metastasis, prostate cancer cells travel through the lymphatic system and/or the bloodstream to other parts of the body, where they lodge and grow secondary tumors.
The spread of cancer can be detected by the presence of prostate cancer cells in areas surrounding the prostate, such as the seminal vesicle, the capsule that surrounds the prostate, and the lymph nodes in the pelvis. This is called locally advanced prostate cancer, indicating that all of the spread is in the region of the prostate. The cancer cells can also spread to other regions of the body. The most common site of distant spread is the bone, but the lung, liver, brain, and other organs could also be involved. When the disease spreads to other sites, it is still considered prostate cancer. It may no longer be curable, but remains highly treatable especially if the spread is not extensive.
How Curable Is Prostate Cancer?
As with all cancers, “cure” rates for prostate cancer describe the percentage of patients remaining disease-free for a specific time. In general, the earlier the cancer is caught and treated, the more likely the patient will remain disease-free.
Approximately 90% of all prostate cancers are detected in the local and regional stages, so the cure rate is very high: Nearly 100% of men diagnosed and treated at this stage will be disease-free after five years. However, prostate cancer is still a deadly disease. Determining which men will die from prostate cancer and which men will die with prostate cancer is an active area of research.
Current studies are looking at men with very small low-risk tumors to decide if immediate aggressive therapy is needed, or if a man can be safely observed without immediate treatment (and side effects) while still preserving his chance of a long-term cure and survival free of disease.
There are also extensive, ongoing efforts to develop urine or blood tests that can accurately tell the difference between cancers that are most likely to become fatal and ones that sit in the prostate without growing or spreading. A PSA test does this modestly, but better tests are needed to prevent over-detection.
The most important part of prostate cancer diagnosis and treatment is the shared decision between you and your physician as to the best course of treatment for you. There is a fine balance of ensuring that aggressive cancer is not missed, while avoiding unnecessary treatment for a non-aggressive form of prostate cancer. You will want to educate yourself as much as possible and ask questions, while the physician must present you with the latest information. There are risks and benefits to any decision made about your prostate cancer, however you and your doctor will tailor the best treatment plan to suit your beliefs and expectations.