Twenty years of screening for breast and prostate cancer—the most diagnosed cancers for women and men—have not brought the anticipated decline in deaths from these diseases, argue experts in an opinion piece published Wednesday in the Journal of the American Medical Association.
Instead, overall cancer rates are higher, more patients are being treated, and the incidence of aggressive or later-stage disease has not significantly decreased, the authors stated. Current screening programs are leading to "potential tumor over-detection and over-treatment," the authors wrote.
"Screening does provide some benefit, but the problem is that the benefit is not nearly as much as we hoped and comes at the cost of over-diagnosis and over-treatment," said Laura Esserman, MD, professor of surgery and radiology, director of the University of California, San Francisco (UCSF) Carol Franc Buck Breast Care Center.
"We need to focus on developing new tools to identify men and women at risk for the most aggressive cancers, to identify at the time of diagnosis those who have indolent or 'idle' tumors that are not life-threatening," added Esserman, who also is co-leader of the breast oncology program at the UCSF Helen Diller Family Comprehensive Cancer Center. "Screening is by no means perfect."
Breast cancer strikes more than 200,000 women annually and kills more than 40,000 each year, reports the American Cancer Society (ACS). Prostate cancer is the most common form of cancer in men and the second most common cause of cancer death after lung cancer. This year, an estimated 192,280 men will be diagnosed with the disease, and 27,360 will die from it, according to estimates from the ACS.
The two diseases account for 26 percent of all cancers in the United States and more than $20 billion is spent annually screening for the two diseases, according to the authors
Due to the high survival rates when the diseases are treated before they spread, screening for both cancers has been promoted, assuming that early detection and treatment will reduce deaths. In turn, much of the U.S. population undergoes routine screening for the cancers: About half of at-risk men have a routine prostate-specific antigen (PSA) test and 75 percent have previously had a PSA test, and about 70 percent of women older than 40 report having had a recent mammogram.
The authors wrote that screenings have resulted in a "significant increase" in early cancers being detected. Because of PSA testing, the chances of a man being diagnosed with prostate cancer have nearly doubled: In 1980, a white man's lifetime risk of the cancer was one in 11; today it is one in six. Similarly, a woman's lifetime risk of breast cancer was one in 12 in 1980; today it is one in eight. If ductal carcinoma in situ is included, the risk of being diagnosed with breast cancer, like prostate cancer, has nearly doubled as well.
The authors found that while deaths have dropped for both cancers over the last 20 years, "the contribution from screening is uncertain." They also found that many patients are undergoing treatment from cancers that actually pose minimal risk.
Periodic screening may find some tumors early, but patients may not be screened often enough for lethal tumors to be detected in time to prevent death, leading the authors to conclude: "Without the ability to distinguish cancers that pose minimal risk from those posing substantial risk and with highly sensitive screening tests, there is an increased risk that the population will be over-treated."
"People will think that we're saying screening is bad, and nothing could be further from the truth," said co-author Ian Thompson, MD, from the University of Texas Health Science Center at San Antonio. "What we are saying is that if you want to stop suffering and death from these diseases, you can't rely on screening alone."
The authors suggested that to improve screening, "a new focus is recommended for research and care to identify markers that discriminate minimal-risk from high-risk disease (and) identify less aggressive interventions for minimal-risk disease to reduce treatment burden for patients and society."
The authors made the following recommendations for early cancer detection and prevention:
- Develop tests to distinguish between low-risk and lethal cancers.
- Reduce treatment for low-risk disease. “Diagnosing cancers that don't kill the patient has led to treatment that may do more harm than good,” they wrote.