What’s New in Prostate Cancer Research?
Research into the causes, prevention, detection, and treatment of prostate is ongoing in many medical centers throughout the world.
New research on gene changes linked to prostate cancer is helping scientists better understand how prostate cancer develops. This could make it possible to design medicines to target those changes. Tests to find abnormal prostate cancer genes could also help identify men at high risk who might benefit from screening or from chemoprevention trials, which use drugs to try to keep them from getting cancer.
Most of the gene mutations that have been studied as factors that might increase prostate cancer risk are from chromosomes that are inherited from both parents. Some research has found that a certain variant of mitochondrial DNA, which is inherited only from a person’s mother, might also raise a man’s risk of developing prostate cancer.
Researchers continue to look for foods (or substances in them) that can help lower prostate cancer risk. Scientists have found some substances in tomatoes (lycopenes) and soybeans (isoflavones) that might help prevent prostate cancer. Studies are now looking at the possible effects of these compounds more closely.
Scientists are also trying to develop related compounds that are even more potent and might be used as dietary supplements. So far, most research suggests that a balanced diet including these foods as well as other fruits and vegetables is probably of greater benefit than taking these substances as dietary supplements.
One vitamin that may be important in prevention is vitamin D. Some studies have found that men with high levels of vitamin D seem to have a lower risk of developing the more lethal forms of prostate cancer. Overall though, studies have not found that vitamin D protects against prostate cancer.
Many people assume that vitamins and other natural substances are safe to take, but recent research has shown that high doses of some may be harmful, including those in supplements marketed specifically for prostate cancer. For example, one study found that men who take more than 7 multivitamin tablets per week may have an increased risk of developing advanced prostate cancer. Another study showed a higher risk of prostate cancer in men who had high blood levels of omega-3 fatty acids. Fish oil capsules, which some people take to help with their heart, contain large amounts of omega-3 fatty acids.
Some research has suggested that men who take a daily aspirin for a long time might have a lower risk of getting and dying from prostate cancer. Still, more research is needed to confirm this, and to confirm that any benefit outweighs potential risks, such as bleeding.
Scientists have also tested certain hormonal medicines called 5-alpha reductase inhibitors as a way of reducing prostate cancer risk. The results of these studies are discussed in Prostate Cancer Prevention and Early Detection.
Doctors agree that the prostate-specific antigen (PSA) blood test is not a perfect test for finding prostate cancer early. It misses some cancers, and in other cases the PSA level is high even when prostate cancer can’t be found. Researchers are working on strategies to address this problem.
One approach is to try to improve on the test that measures the total PSA level, as described in Prostate Cancer Prevention and Early Detection.
Another approach is to develop new tests based on other forms of PSA, or other tumor markers. Several newer tests seem to be more accurate than the PSA test, including:
- The phi, which combines the results of total PSA, free PSA, and proPSA to help determine how likely it is that a man has prostate cancer that might need treatment
- The 4Kscore test, which combines the results of total PSA, free PSA, intact PSA, and human kallikrein 2 (hK2), along with some other factors, to help determine how likely a man is to have prostate cancer that might need treatment
- Tests such as Progensa that look at the level of prostate cancer antigen 3 (PCA3) in the urine after a digital rectal exam (DRE). (The DRE pushes some of the prostate cells into the urine.) The higher the level, the more likely that prostate cancer is present.
- Tests that look for an abnormal gene change called TMPRSS2:ERG in prostate cells in urine collected after a DRE. This gene change is found in some prostate cancers, but it is rarely found in the cells of men without prostate cancer.
- ConfirmMDx, which is a test that looks at certain genes in the cells from a prostate biopsy sample
These tests aren’t likely to replace the PSA test any time soon, but they might be helpful in certain situations. For example, some of these tests might be useful in men with a slightly elevated PSA, to help determine whether they should have a prostate biopsy. Some of these tests might be more helpful in determining if men who have already had a prostate biopsy that didn’t find cancer should have another biopsy. Doctors and researchers are trying to determine the best way to use each of these tests.
Doctors doing prostate biopsies often rely on transrectal ultrasound (TRUS), which creates black and white images of the prostate using sound waves, to know where to take samples from. But standard ultrasound may not detect some areas containing cancer.
A newer approach is to measure blood flow within the gland using a technique called color Doppler ultrasound. (Tumors often have more blood vessels around them than normal tissue.) It may make prostate biopsies more accurate by helping to ensure the right part of the gland is sampled.
An even newer technique may enhance color Doppler further. In this approach, the patient is first injected with a contrast agent containing microbubbles, which helps improve the ultrasound images. Promising results have been reported, but more studies will be needed before its use becomes common.
Doctors are also studying whether MRI can be combined with TRUS to help guide prostate biopsies in men who previously had negative TRUS-guided biopsies but when the doctor still suspects cancer.
Determining the stage (extent) of prostate cancer plays a key role in determining a man’s treatment options. But imaging tests for prostate cancer such as CT and MRI scans can’t detect all areas of cancer, especially small areas of cancer in lymph nodes.
A newer method known as multiparametric MRI can be used to help determine the extent of the cancer and how aggressive it might be, which might affect a man’s treatment options. This test involves getting a standard MRI, and then getting at least one other type of MRI (such as diffusion weighted imaging [DWI], dynamic contrast enhanced [DCE] MRI, or MR spectroscopy). The results of the different scans are then taken into account.
Another newer method, called enhanced MRI, may help find lymph nodes that contain cancer cells. Patients first have a standard MRI. They are then injected with tiny magnetic particles and have another scan the next day. Differences between the 2 scans point to possible cancer cells in the lymph nodes. Early results of this technique are promising, but it needs more research before it becomes widely used.
A newer type of positron-emission tomography (PET) scan that uses radioactive carbon acetate instead of labeled glucose (sugar) may also be helpful in detecting prostate cancer in different parts of the body, as well as helping to determine if treatment is working. This technique is now being studied.
Newer treatments are being developed, and improvements are being made among many standard prostate cancer treatment methods.
Doctors are constantly improving the surgical techniques used to treat prostate cancer. The goal is to remove all of the cancer while lowering the risk of complications and side effects from the surgery.
As described in Radiation Therapy for Prostate Cancer, advances in technology are making it possible to aim radiation more precisely than in the past. Current methods such as conformal radiation therapy (CRT), intensity modulated radiation therapy (IMRT), and proton beam radiation help doctors avoid giving radiation to normal tissues as much as possible. These methods are expected to increase the effectiveness of radiation therapy while reducing the side effects.
Technology is making other forms of radiation therapy more effective as well. New computer programs allow doctors to better plan the radiation doses and approaches for both external radiation therapy and brachytherapy. Planning for brachytherapy can now even be done during the procedure (intraoperatively).
Newer treatments for early stage cancers
Researchers are looking at newer forms of treatment for early-stage prostate cancer. These new treatments could be used either as the first type of treatment or after radiation therapy in cases where it was not successful.
One treatment, known as high-intensity focused ultrasound (HIFU), destroys cancer cells by heating them with highly focused ultrasonic beams. This treatment has been used in some countries for a while, but it has just recently become available in the United States. Its safety and effectiveness are now being determined.
Nutrition and lifestyle changes
Many studies have looked at the possible benefits of specific nutrients (often as supplements) in helping to treat prostate cancer, although most of this research is still ongoing. Some compounds being studied include extracts from pomegranate, green tea, broccoli, turmeric, flaxseed, and soy.
Some early research has found that in men with a rising PSA level after surgery or radiation therapy, drinking pomegranate juice or taking a pomegranate extract may slow the time it takes for the PSA level to double. Larger studies are now looking for possible effects of pomegranate juices and extracts on prostate cancer growth.
Some encouraging early results have also been reported with flaxseed supplements. One small study in men with early prostate cancer found that daily flaxseed seemed to slow the rate at which prostate cancer cells multiplied. More research is needed to confirm this finding.
A recent study showed that taking soy supplements after surgery (radical prostatectomy) for prostate cancer did not lower the risk of the cancer coming back.
One study has found that men who choose not to have treatment for their localized prostate cancer may be able to slow its growth with intensive lifestyle changes. The men in the study ate a vegan diet (no meat, fish, eggs, or dairy products) and exercised frequently. They also took part in support groups and yoga. After one year the men saw, on average, a slight drop in their PSA level. It isn’t known if this effect will last since the report only followed the men for 1 year. The regimen may also be hard for some men to follow.
Several newer forms of hormone therapy have been developed in recent years. Some of these may be helpful even if standard forms of hormone therapy are no longer working.
Some examples include abiraterone (Zytiga) and enzalutamide (Xtandi), which are described in Hormone Therapy for Prostate Cancer. Others are now being studied as well.
5-alpha reductase inhibitors, such as finasteride (Proscar) and dutasteride (Avodart), are drugs that block the conversion of testosterone to the more active dihydrotestosterone (DHT). These drugs are being studied to treat prostate cancer, either to supplement active surveillance or if the PSA level rises after prostatectomy.
Studies in recent years have shown that many chemotherapy drugs can affect prostate cancer. Some, such as docetaxel (Taxotere) and cabazitaxel (Jevtana) have been shown to help men live longer.
Results from recent large studies have found that in men with metastatic prostate cancer, giving chemotherapy (docetaxel) earlier in the course of the disease might help them live longer. These results are encouraging, but these studies were done before newer forms of hormone therapy (abiraterone and enzalutamide) became available, so it’s not clear if the results would be the same today.
Other new chemo drugs and combinations of drugs are being studied as well.
The goal of immunotherapy is to boost the body’s immune system to help fight off or destroy cancer cells.
Unlike vaccines against infections like measles or mumps, prostate cancer vaccines are designed to help treat, not prevent, prostate cancer. One possible advantage of these types of treatments is that they seem to have very limited side effects. An example of this type of vaccine is sipuleucel-T (Provenge), which has received FDA approval (described in Vaccine Treatment for Prostate Cancer).
Several other types of vaccines to treat prostate cancer are being tested in clinical trials.
One example is PROSTVAC, which uses 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. Early results with this vaccine have been promising, and a larger study is now under way.
Immune checkpoint inhibitors
An important part of the immune system is its ability to keep itself from attacking other normal cells in the body. To do this, it uses “checkpoints” – molecules on immune cells that need to be turned on (or off) to start an immune response. Cancer cells sometimes use these checkpoints to avoid being attacked by the immune system. But newer drugs that target these checkpoints hold a lot of promise as cancer treatments.
For example, newer drugs such as pembrolizumab (Keytruda) and nivolumab (Opdivo) target the immune checkpoint protein PD-1. In some other cancers, these types of drugs have been shown to shrink a larger portion of tumors. Studies are now being done to see how well they might work against prostate cancer.
Another example is the drug ipilimumab (Yervoy), which targets a checkpoint protein called CTLA-4 on certain immune cells. This drug is already used to treat some other cancers, and is now being tested in men with advanced prostate cancer.
One promising approach for the future might be to combine a checkpoint inhibitor with a prostate cancer vaccine. This might strengthen the immune response and help the vaccine work better.
Targeted therapy drugs
Newer drugs are being developed that target specific parts of cancer cells or their surrounding environments. Each type of targeted therapy works differently, but all alter the way a cancer cell grows, divides, repairs itself, or interacts with other cells.
For example, drugs called angiogenesis inhibitors target the growth of new blood vessels (angiogenesis) that tumors need to grow. Several angiogenesis inhibitors are being tested in clinical trials.
Treating cancer that has spread to the bones
Doctors are studying the use of radiofrequency ablation (RFA) to help control pain in men whose prostate cancer has spread to one or more areas in the bones. During RFA, the doctor uses a CT scan or ultrasound to guide a small metal probe into the area of the tumor. A high-frequency current is passed through the probe to heat and destroy the tumor. RFA has been used for many years to treat tumors in other organs such as the liver, but its use in treating bone pain is still fairly new. Still, early results are promising.
Last Medical Review: February 16, 2016 Last Revised: March 11, 2016