An essay co-written by a Wayne State University School of Medicine physician-researcher and published in the New England Journal of Medicine this week suggests that screenings and mammograms may not be effective in detecting metastatic breast cancer early enough.
The United States rates of metastatic breast cancer - a form that has spread beyond the initial site and is considered the most deadly form of breast cancer - have not changed since 1975 despite the widespread recommendation and use of mammograms for detection.
"The stable incidence of metastatic breast cancer suggests two things. First, the underlying probability of developing this form of breast cancer is itself stable. Second, screening mammography has been unable to identify at an earlier stage, before symptoms appear, cancers that are destined to become metastatic," David Gorski, M.D., Ph.D., F.A.C.S., associate professor of Surgery and chief of the Breast Surgery Section for the WSU School of Medicine, and his co-authors write in "Trends in Metastatic Breast and Prostate Cancer — Lessons in Cancer Dynamics," in the Oct. 29 edition of the New England Journal of Medicine.
The lack of change in the rates of metastatic breast cancer is consistent with the hypothesis that breast cancer is a systemic disease by the time it becomes detectable, writes Dr. Gorski, medical director of the Alexander J. Walt Comprehensive Breast Center of the Barbara Ann Karmanos Cancer Institute. His co-authors are Peter Albertsen, M.D., professor of Surgery for the University of Connecticut Health Center; and lead author H. Gilbert Welch, M.D., M.P.H., professor of Medicine for Dartmouth Medical School.
Either mammography isn't sensitive enough to identify metastatic breast cancers, the trio writes, or the disease doesn't fit the traditionally accepted theory that cancers destined to spread should be able to be identified - and treated - at an earlier stage before they spread to other areas of the body.
The authors compared the stagnant rates of metastatic breast cancer with rates of metastatic prostate cancer in men. In contrast to the decades of steady rates of breast cancer, prostate cancer rates have seen a steep decline - by 50 percent - since 1988.
The difference is most likely the result of prostate-specific antigen, or PSA screening, for prostate cancer. The rapid adaptation of PSA testing led to a "dramatic spike" in the diagnosis of all types of prostate cancer in the early 1990s. Patient data over the last few decades supports the hypothesis that PSA screening leads to earlier diagnosis of prostate cancers that will spread, the authors write. Metastatic prostate cancer, they said, appears to fit the theory that finding the cancer earlier will lead to more successful treatment and mortality rates.
The discordant trends between breast and prostate cancers, the authors write, could reflect "distinct disease dynamics," but they also may be the result of differing screening strategies.
Mammography, Dr. Gorski said, "represents an anatomical search for a structural abnormality, while PSA screening utilizes a biochemical assay to detect a tumor marker. It's possible that the latter is a much more sensitive indicator of disease. Were a similar breast cancer assay discovered - and a similar organ-wide sampling strategy used - then perhaps fewer women would present with metastatic breast cancer."
Whether such a test would affect mortality rates in breast cancer patients represents a different question, he said.
"Given the increasing enthusiasm for genomic, proteomic and immunosignature testing to enhance early cancer detection, we believe it will be critical to consider the variability in cancer dynamics," the authors write. Some cancers are destined to be systemic and others are not. "Conflating these types of lesions could result in screening programs that are not helpful and administration of treatment that is either not needed or not effective."