U.S. shows significant drop in prostate cancer rates
While doom and gloom are generally associated with cancer and cancer survival rates, there is good news regarding prostate cancer.
According to the study results presented April 2 during the American Association for Cancer Research annual meeting, prostate cancer incidence and mortality rates are decreasing or stabilizing in most parts of the world. The United States is showing the most significant drop in frequency.
However, prostate cancer remains the second most commonly diagnosed cancer and the sixth leading cause of cancer death among men worldwide.
“Previous studies have indicated significant variation in prostate cancer rates, due to factors including detection practices, availability of treatment, and genetic factors,” said MaryBeth Freeman, MPH, senior associate scientist, Surveillance Research, at the American Cancer Society in Atlanta. “By comparing rates from different countries, we can assess differences in detection practices and improvements in treatment.” (1)
Of the 44 countries examined for incidence data, prostate cancer rates during the most recent 5-year period increased in four countries, with Bulgaria showing the most significant increase. Rates decreased in seven countries. Rates stabilized in the other 33 countries.
Among the 71 countries analyzed for mortality rates, rates decreased in 14 countries, increased in three countries, and remained stable in 54 countries.
Globally, as of 2012, prostate cancer was the most commonly diagnosed cancer among men in 96 countries and the leading cause of death in 51 countries.
The American Cancer Society estimates 174,650 new cases of prostate cancer will be diagnosed in the U.S. during 2019. The incidence of prostate cancer is about 60% higher in
blacks than in whites for reasons that remain unclear. (2)
The majority (90%) of prostate cancers are discovered at a local or regional stage, for which the 5-year relative survival rate approaches 100%. The 5-year survival for disease diagnosed at a distant stage is 30%. The 10-year survival rate for all stages combined is 98%.
Importance of PSA screening
Freeman said the study confirmed the impact of prostate-specific antigen (PSA) screening. She explained that in the U.S., prostate cancer incidence rates increased from the 1980s to the early 1990s, then declined from the mid-2000s through 2015, primarily due to increased use of PSA screening. This type of testing is less available in lower-income nations, contributing to diagnosis at later stages and higher mortality rates, Freeman said.
The National Cancer Institute notes prostate-specific antigen is a protein produced by healthy, as well as malignant, cells of the prostate gland. The PSA test measures the level of PSA in a man’s blood. For this test, a blood sample is sent to a laboratory for analysis. The results are usually reported as nanograms of PSA per milliliter (ng/mL) of blood. (3)
The blood level of PSA is often elevated in men with prostate cancer. The PSA test was approved by the FDA in 1986 to monitor the progression of prostate cancer in men who had already been diagnosed with the disease. In 1994, the FDA approved the use of the PSA test in conjunction with a digital rectal exam (DRE) to test asymptomatic men for prostate cancer. Men who report prostate symptoms often undergo PSA testing (along with a DRE) to help doctors determine the nature of the problem.
In addition to prostate cancer, many non-cancerous conditions can cause a man’s PSA level to rise. The most frequent benign prostate conditions that cause an elevation in PSA level are prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH) (enlargement of the prostate). There is no evidence that prostatitis or BPH leads to prostate cancer, but it is possible for a man to have one or both of these conditions and to develop prostate cancer as well.
Until about 2008, some doctors and professional organizations encouraged yearly PSA screening for men beginning at age 50. Some organizations recommended that men who are at higher risk of prostate cancer, including black men and men whose father or brother had prostate cancer, begin screening at age 40 or 45.
However, as more was learned about both the benefits and harms of prostate cancer screening, some organizations began to caution against routine population screening. Most organizations recommend that men who are considering PSA screening first discuss the risks and benefits with their doctors.
Cautions for PSA testing
The NCI notes detecting prostate cancer early may not reduce the chance of dying from prostate cancer. When used in screening, the PSA test can help detect small tumors that do not cause symptoms. Finding a small tumor, however, may not necessarily reduce a man’s chance of dying from prostate cancer. Many tumors found through PSA testing grow so slowly that they are unlikely to threaten a man’s life.
Detecting tumors that are not life-threatening is called “overdiagnosis,” and treating these tumors is called “overtreatment.”
Overtreatment exposes men unnecessarily to the potential complications and harmful side effects of treatments for early prostate cancer, including surgery and radiation therapy. The side effects of these treatments include urinary incontinence (inability to control urine flow), problems with bowel function, erectile dysfunction (loss of erections, or having erections that are inadequate for sexual intercourse), and infection.
Also, finding cancer early may not help a man who has a fast-growing or aggressive tumor that may have spread to other parts of the body before being detected.
Also, the PSA test may give false-positive or false-negative results. A false-positive test result occurs when a man’s PSA level is elevated, but no cancer is actually present. A false-positive test result may create anxiety for a man and his family and lead to additional medical procedures, such as a prostate biopsy, that can be harmful. Possible side effects of biopsies include serious infections, pain, and bleeding.
Most men with an elevated PSA level turn out not to have prostate cancer; only about 25% of men who have a prostate biopsy due to a high PSA level actually are found to have prostate cancer when a biopsy is done.
A false-negative test result occurs when a man’s PSA level is low even though he actually has prostate cancer. False-negative test results may give a man, his family, and his doctor false assurance that he does not have the disease, when he may, in fact, have a cancer that requires treatment.
Citations
(1) American Association for Cancer Research. Prostate cancer incidence and mortality have declined in most countries. https://www.eurekalert.org/pub_releases/2019-04/aafc-pci032519.php
(2) Cancer Facts & Figures 2019. American Cancer Society. https://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/cancer-facts-figures-2019.html
(3) National Cancer Institute. Prostate-Specific Antigen (PSA) Test Fact Sheet. https://www.cancer.gov/types/prostate/psa-fact-sheet