Is it possible for this widely heralded screening tool to miss the presence of cancer at an early stage?
The occurrence of metastatic breast cancer essentially remained unchanged since 1975, despite the widespread use and promotion of breast cancer screening – mostly through mammography – since the 1980s.
In an article published in the New England Journal of Medicine, researchers probed the role of screening in the rates of metastatic breast and prostate cancers. While advanced breast cancer rates remained stable since 1975, the incidence for advanced prostate cancer had been slashed by half since 1988.
What could explain the difference in trends? According to authors Dr. H. Gilbert Welch, Dr. David Gorski, and Dr. Peter Albertsen, mammograms may have been unable to identify the cancer at an earlier stage prior to symptoms appearing.
Another explanation is that breast cancer does not readily start in one place and then spread, with expert Dr. Bernard Fisher arguing that by the time of detection it has already turned into a systemic illness.
Over the past 37 years, the mean age at diagnosing women ages 40 and above had remained at 63.7 years. Authors proposed that mammograms may not be “sensitive enough” for identifying cancer early on.
Prostate-specific antigen (PSA) screening, in contrast, was recognized for the sharp decline in advanced prostate cancer cases. Its rapid uptake was deemed instrumental in “a dramatic spike” in diagnosing prostate cancer.
Based on data from the National Cancer Institute, from about 70 per 100,000 men in the early 1990s, prostate cancer rates plunged to fewer than 30 per 100,000 after a decade.
The authors, however, highlighted the difference in the two cancer tests: mammograms comprise an “anatomical search for a structural abnormality,” while PSA screening uses a biomarker found in blood. “It’s possible that the latter is a much more sensitive indicator of disease burden,” the researchers added.
In the new mammography guidelines from the American Cancer Society, the recommended age for annual screening was raised from 40 to 45 for females “of average risk for breast cancer,” while biennial mammography was suggested for women ages 55 to 74.
Women are deemed of average risk for breast cancer if they do not have a personal or family history for the condition, a genetic mutation that increases risk, or received radiation therapy to the chest prior to age 30.
In a commentary, science and medical law expert Diane L. Danois urged women to challenge the new guidelines if they believe they need to be screened earlier. She also encouraged maintaining personal health records, knowing one’s legal rights, and be one’s own “patient advocate.”
“Know your risk factors! If you are a high-risk patient, discuss with your physician your best screening options,” she said.
Photo: Ed Uthman | Flickr