Thursday, February 25, 2010
The Evidence for Colonoscopies as a Cancer Screening Test
This post by Harriet Hall, MD, originally appeared at Better Health.
Everybody knows that colonoscopy is the best test to screen for colorectal cancer and that colonoscopies save lives. Everybody may be wrong. Colonoscopy is increasingly viewed as the gold standard for colorectal cancer screening, but its reputation is not based on solid evidence. In reality, it is not yet known for certain whether colonoscopy can help reduce the number of deaths from colorectal cancer. Screening with fecal occult blood testing (FOBT) and flexible sigmoidoscopy are supported by better evidence, but questions remain. It seems our zeal for screening tests has outstripped the evidence.
Statistics show that the lifetime risk for an adult American to develop colorectal cancer is approximately 6%. Colorectal cancer is the second leading cause of cancer deaths in the U.S. In the U.S. there are currently 146,970 new cases and 50,630 deaths each year. Between 1973 and 1995, mortality from colorectal cancer declined by 20.5%, and incidence declined by 7.4% in the U.S.
The U.S. Preventive Services Task Force (USPSTF) recommends screening for colorectal cancer using fecal occult blood testing, sigmoidoscopy, or colonoscopy, in adults, beginning at age 50 years and continuing until age 75 years.
The American Cancer Society divides the available tests into these two categories and makes these recommendations for frequency of testing:
Tests that find polyps and cancer
--flexible sigmoidoscopy every 5 years
--colonoscopy every 10 years
--double contrast barium enema every 5 years
--CT colonography (virtual colonoscopy) every 5 years
Tests that mainly find cancer
--fecal occult blood test (FOBT) every year
--fecal immunochemical test (FIT) every year
--stool DNA test (sDNA), interval uncertain
Screening by colonoscopy seems to make more sense than other screening methods, because you can actually see the entire inside of the colon. Colon cancer is preceded by polyps and adenomas that progress to cancer. When a polyp is seen, it can be removed during the procedure. In this study, colonoscopic polypectomy resulted in a lower than expected incidence of colorectal cancer. But other studies suggest that the progression to cancer is not a steady process, and that adenomas may regress.
There is good evidence here and here that any benefit of colonoscopy is restricted to left-sided colon cancers, with no impact on right-sided colon cancer; we don't understand why. Some possible explanations are discussed here.
There are pros and cons to each of the different screening tests. Barium enemas and CT virtual colonoscopy involve significant doses of radiation. Colonoscopy only needs to be done every 10 years, but it involves an uncomfortable bowel prep, requires sedation, can cause serious complications like bowel perforation, and is unacceptable to some patients. FOBT screening is painless and harmless but has a lot of false positives and requires annual testing. Getting patients to come back every year for FOBT is problematic. Compliance and cost must be considered. Colonoscopy is expensive and there are not enough colonoscopists to screen everyone.
Apart from all those peripheral considerations, what do we know about the bottom line: the ability of each screening method to prevent deaths from colon cancer? According to the National Cancer Institute,
--Studies have shown that FOBT, when performed every 1 to 2 years in people ages 50 to 80, can help reduce the number of deaths due to colorectal cancer by 15 to 33%.
--Studies suggest that regular screening with sigmoidoscopy after age 50 can help reduce the number of deaths from colorectal cancer, perhaps by as much as 50%, but the quality of evidence is not as good as for FOBT.
--It is not yet known for certain whether colonoscopy can help reduce the number of deaths from colorectal cancer.
No randomized controlled trials have tested whether colonoscopy reduces the incidence of colorectal cancer. Support for the role of colonoscopy in colorectal cancer prevention derives from indirect evidence and observational studies.
There is an excellent review of all the pertinent studies here. Even though studies show that screening can reduce disease-specific mortality from colorectal cancer, there is little evidence that it reduces all-cause mortality. So as far as we know, screening probably won't prolong your life. It seems like it should: I don't understand why it doesn't, and it bothers me. This certainly isn't the message we're getting from the media and from the medical profession.
I'm guessing that if the appropriate studies were done and the technique of colonoscopy were optimized, a reduction in colon cancer deaths would be demonstrated. I'm guessing that colonoscopy would detect more cancers and precancerous lesions than FOBT or sigmoidoscopy, but I'm wondering whether the benefits of colonoscopy would outweigh the additional cost and risks compared to other screening methods. And I'm disturbed that a reduction in all-cause mortality has not yet been clearly shown for any screening method. We need more research to help us understand these issues.
Pending better evidence, I support the current USPSTF recommendations. I think patients should be told the pros and cons and choose which screening test they prefer. I have chosen annual FOBT for myself.
This post originally appeared on Better Health, a network of popular health bloggers brought together by Val Jones, MD. Better Health's mission is to support and promote health care professional bloggers, provide insightful and trustworthy health commentary, and help to inform health policy makers about the provider point of view on health care reform, science, research and patient care.
Contact ACP Internist
Send comments to ACP Internist staff at email@example.com.
- QD: News Every Day--Can't they wait until it's ove...
- Here We Go Again
- QD: News Every Day--Amid Summit Fight's Eve
- QD: News Every Day--counting down to Thursday's su...
- QD: News Every Day--president releases new health ...
- Medical News of the Obvious
- Confidence And Doubt: The Language Of Clinician Ve...
- QD: News Every Day--health reform smacks into heal...
- QD: News Every Day--Politics and health care in Am...
- Primary Care Physicians Are All One Breath Away Fr...
Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.
And Thus, It Begins
Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.
Controversies in Hospital
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Richmond, Va., with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).
db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.
Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.
Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.
Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.
William Hersh, MD, FACP, Professor and Chair, Department of Medical Informatics & Clinical Epidemiology, Oregon Health & Science University, posts his thoughts on various topics related to biomedical and health informatics.
David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.
Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.
Elaine Schattner, MD, FACP, shares her ideas on education, ethics in medicine, health care news and culture. Her views on medicine are informed by her past experiences in caring for patients, as a researcher in cancer immunology, and as a patient who's had breast cancer.
Mired in MedEd
Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).
David M. Sack, MD, FACP, practices general gastroenterology at a small community hospital in Connecticut. His blog is a series of musings on medicine, medical care, the health care system and medical ethics, in no particular order.
Reflections of a Grady
Kimberly Manning, MD, FACP, reflects on the personal side of being a doctor in a community hospital in Atlanta.
The Blog of Paul Sufka
Paul Sufka, MD, ACP Member, is a board certified rheumatologist in St. Paul, Minn. He was a chief resident in internal medicine with the University of Minnesota and then completed his fellowship training in rheumatology in June 2011 at the University of Minnesota Department of Rheumatology. His interests include the use of technology in medicine.
Technology in (Medical)
Neil Mehta, MBBS, MS, FACP, is interested in use of technology in education, social media and networking, practice management and evidence-based medicine tools, personal information and knowledge management.
Peter A. Lipson,
Peter A. Lipson, MD, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. The blog, which has been around in various forms since 2007, offers musings on the intersection of science, medicine, and culture.
Why is American Health Care So Expensive?
Janice Boughton, MD, FACP, practiced internal medicine for 20 years before adopting a career in hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling.
World's Best Site
Daniel Ginsberg, MD, FACP, is an internal medicine physician who has avidly applied computers to medicine since 1986, when he first wrote medically oriented computer programs. He is in practice in Tacoma, Washington.
Other blogs of note:
American Journal of
Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.
The Public Library of Science's open access materials include a blog.
One of the most popular anonymous blogs written by an emergency room physician.