Screening for prostate cancer

Jun 24, 2017

As men age, the likelihood of being diagnosed with prostate cancer goes up. And since prostate cancer is the most common cancer for American men, how to screen for this disease has been quite controversial.

This week on “Take Care,” Dr. Kirsten Bibbins-Domingo discusses the latest recommendations for prostate cancer screening. Bibbins-Domingo chairs the U.S. Preventive Services Task Force that issued new recommendations in April 2017. Bibbins-Domingo is professor of medicine and of epidemiology and biostatistics at the University of California, San Francisco.

While routine screening can identify early stage cancers, concerns about over diagnosis, false positives, and side effects of treatment such as incontinence or erectile dysfunction led to a controversial 2012 recommendation not to screen for prostate cancer.

But some medical experts did not agree with that recommendation. This year’s guidelines advise men age 55-69 to make an individualized decision about prostate cancer screening with their doctor. Those older than 70 are not advised to have screening.

The prostate & prostate cancer basics

If it weren’t for prostate cancer, many average people might not even know what the prostate is. It’s a gland in men’s lower genitalia area. You can’t see it or feel it, but it’s essential to a man’s normal functioning.

The prostate develops cancer, and it’s the most common form of cancer in men as they age. And Bibbins-Domingo says what’s unique about prostate cancer is that it’s more common as men age. The average age at diagnosis is well into the 70s.

Often times it’s a slow-growing cancer.

“While we are all concerned about cancers, many types of cancers in the prostate are those that won’t cause a man a problem during their lifetime,” Bibbins-Domingo said.

If a man has a father, brother or uncle who has had prostate cancer, it puts them at higher risk. Bibbins-Domingo says patients need to make sure their doctors are aware of family history when they are making a decision about screening.

“Unfortunately we don’t have a lot of good studies about what we should be doing with men who have a family history, whether we should be screening earlier or more often,” Bibbins-Domingo said.

African-American men have twice the rates of developing prostate cancer and if they develop it, they are twice as likely to die. Bibbins-Domingo says that’s also a factor for African-Americans to consider when making the choice to be screened. But again, Bibbins-Domingo says not enough studies exist of African-American men to determine what’s best to do differently.

Change in guidelines

Bibbins-Domingo says the U.S. Preventive Services Task Force makes it’s recommendations solely based on the science of the time.

In 2012, she says what the body of evidence reviewed told them that the benefit to screening is that if 1,000 men are screened, one or two avoid dying.

But while many men who get diagnosed have a type of prostate cancer that won’t cause a problem, most men are treated. Of those diagnosed, 90 percent were treated. Bibbins-Domingo says the harms that come along with treating a type of cancer that’s not going to cause a problem is what led the task force to say in 2012 this is not something we should be routinely doing in all men.

Fast forward to 2017, the reason the task force shifted is because of new evidence, says Bibbins-Domingo. In the five years in between there were several new types of studies, about the benefits of screening. Men who are screened can avoid dying and avoid cancers that spread.

Bibbins-Domingo says that there are newer strategies to treating prostate cancer that allow men who have low-grade prostate cancer to delay or perhaps even avoid more aggressive treatments with surgery or radiation. That’s called active surveillance.

The combination of those two lines of evidence led to the change in recommendation, says Bibbins-Domingo. She says the balance of benefits and harms have shifted. The balance is still close, and the task force is not saying all men should be screened. It recommends that men between the ages of 55-69 have a conversation with their doctor, understand the benefits and harms and make the best decision for themselves.

How does screening work?

The screening approach for prostate cancer that is widespread is use of a blood test called PSA, or “prostate specific antigen.” That's a protein found in the blood. Increases in PSA can be the signal to lead clinicians to go looking for cancer. But the test is actually one of the main challenges for men and doctors deciding what to do.

“It’s just not a great test. There are many things that can cause a PSA to be elevated,” Bibbins-Domingo said,

When men age, their prostate enlarges, and even when the enlargement is not due to cancer, it can cause rise in PSA. So, the rise in the PSA buy itself needs to have follow-up testing. More blood tests or often times, biopsies of the prostate to help determine if there’s cancer.

If you screen 1,000 men over 10 years, about ¼ of them will have a high PSA, says Bibbins-Domingo, and that then requires additional testing to determine whether there’s actually cancer present.

The issues with the PSA test is one of the areas that the task force called for more research.

“Everyone in this area [of research] agrees that the PSA is not a great test. We need a better test,” Bibbins-Domingo said. She said there needs to be more studies and research on better studies to identify cancer, and particularly those cancers that are going to cause a man problems in his lifetime.

Downside of screening -- too much treatment

The downside of screening is really what happens after the PSA test. In order to get the benefit of screening, you also have to go through all of these other steps -- the follow up tests, biopsies and treatments. It’s that entire cascade that leads to the benefits.

And in some men it’s that entire cascade that can lead to the harms. Bibbins-Domingo says 20 to 50 percent of men who get diagnosed with prostate cancer have an over diagnosis have a type of cancer that may not cause them a problem during their lifetime.

“This is a pretty high rate of over diagnosis compared to other cancers,” Bibbins-Domingo said.

And the challenge is the fact, Bibbins-Domingo says, that doctors treat nearly all of those men. Five years ago, 90 percent of men who were diagnosed were treated. And the treatment -- surgery and radiation -- have side-effects associated with them, like impotence and incontinence, that occur in most men, she said.

If 2017, the new evidence shows that in men with low-grade prostate cancer, using a strategy known as active surveillance can delay or avoid treatments with surgery or radiation until it’s determined that the cancer is actually progressing. Active surveillance is not just watchful waiting, it means that these men actually have to do more biopsies and blood tests, because the strategy is to treat when there’s more evidence that the cancers are becoming more active.

“Of course we are concerned about prostate cancer and how to reduce a man’s chance of dying of prostate cancer. As the number one cancer in older men, we know this is of concern,” Bibbins-Domingo said.

“The challenge is being able to determine the best strategies for screening to give men the information about the state of the science as it is right now. And then help men to think about screening in the context of many choices they have to make about what they would like to do to lead long, healthy lives.”