Cancer screening has been the hallmark of the war against cancer in the past decades. It is commonly believed that regular screening for cancer will lead to early detection of cancer, that is, cancers will be detected at earlier, treatable stages rather at later, fatal stages. Most major cancers detected at earlier stages have very high rates of survival. For instance, the 5-year survival rate of stage I breast cancer is almost 95-97%, while the 5-year survival rate of stage IV breast cancer is merely 25% (see Cancer Statistics, 2009). Similarly, the survival rate for early-stage prostate cancer is almost 100%.
However, recent evidences seem to indicate that cancer screening might not be effective as once thought in terms of reducing cancer mortality. In an article published in the prestige Journal of American Medical Association in October 2009, Dr. Laura Esserman and colleagues argued that cancer screening might increase the detection of early-stage cancers, however, a significant portion of these cancers might not become lethal anyway. That is the patients might die WITH cancers rather OF cancers. This is particularly true for prostate cancer and to some extent for breast cancer.
In the past decade, the incidence of prostate cancer has more than doubled. One in 6 men will be diagnosed with prostate cancer in their life-time (Jemal, Siegel et al. 2009). This is due to widespread use of serum prostate-specific antigen (PSA) testing since the 1990s. The problem is that PSA testing is not specific to prostate cancer. Non-cancerous conditions such as benign prostatic hyperplasia also increase PSA levels. The potential harms of PSA testing include over-diagnosis, complications of prostate biopsies and additional medical costs. There is no evidence that screening for prostate cancer by prostate-specific antigen (PSA) reduces prostate cancer mortality or improve life expectancy. Rather men who are diagnosed with early-stage prostate cancer will have to go through painful treatment and suffer from anxiety/stress followed cancer diagnosis.
Breast cancer screening, to some extent, also leads to high rates of over-diagnosis. Although many experts believe that mammogram screening can reduce breast cancer mortality up to 40% through earlier detection, the existing evidences seem to point toward a 20-25% reduction.
Colorectal cancer screening remains the poster child for cancer screening. This is because screening by colonoscopy not only allow early detection of carcinomas but detection and removal of adenomas, which are the precursors to cancers. Thus, colorectal cancer screening is not only screening – it is a preventive method. However, many argued that removal of every single adenoma might be too aggresive. Also, colonoscopy every 10 year maybe over-screened. The U.S Preventive Service Task Force recommends to stop screening for colorectal cancer after age 75. They argued that it takes up to 10 years to realize the benefits of colorectal cancer screening. For people older than age 75, their life expectancy might not be long enough for colorectal cancer screening to make a difference. Furthermore, complications of colonoscopy increase with older ages.
At the end the decision to screen or not to screen should depend on individual. Consult your physician about your cancer risks according to your personal risk factors and family history. If your cancer risk is high, cancer screening is definitely worth consideration.
1) American Cancer Society, Cancer Statistics http://www.cancer.org/docroot/STT/STT_0.asp
2) Laura Esserman, MD, MBA; Yiwey Shieh, AB; Ian Thompson, MD, Journal of American Medical Association (JAMA), 2009;302(15):1685-1692.
3) Lin, K., R. Lipsitz, et al. (2008). “Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force.” Ann Intern Med149(3): 192-9.
4) U.S. Preventive Service Task Force Colorectal Cancer Screening Guideline
5) Jemal, A., R. Siegel, et al. (2009). “Cancer statistics, 2009.” CA Cancer J Clin59(4): 225-49.