Course Authors
Susan C. Stewart, M.D.
Dr. Stewart reports no commercial conflict of interest.
This activity is made possible by an unrestricted educational grant from the Novartis Foundation for Gerontology.
Estimated course time: 1 hour(s).
Albert Einstein College of Medicine – Montefiore Medical Center designates this enduring material activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
In support of improving patient care, this activity has been planned and implemented by Albert Einstein College of Medicine-Montefiore Medical Center and InterMDnet. Albert Einstein College of Medicine – Montefiore Medical Center is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.
Upon completion of this Cyberounds®, you should be able to:
Identify the type of polyp that is the most common precursor of colorectal cancer
Determine whether a woman or a man is at average, moderate or high risk for developing colorectal cancer
Recommend to patients appropriate colorectal cancer screening.
Introduction
There's an odd perception out there, particularly among the public, that women don't get colorectal cancer (CRC). It's a little like the "women don't get lung cancer" in the 60s or the "women don't get heart attacks" of the 70s and 80s. Women do get CRC and in almost the same numbers as men, at the same ages as men and require the same screening as men.
In 1999, the American Cancer Society predicts that 129,400 Americans will be diagnosed with colorectal cancer, 62,300 men and 67,000 women. The ACS also predicts that 56,600 Americans will die from colorectal cancer, 27,800 men and 28,800 women. Although CRC is fourth in incidence after lung, breast and prostate cancer, it is second in mortality after lung cancer because patients with breast and prostate cancer have high survival rates.(1)
Yet women are not being screened at the same rates as men. The 1995 BFRSS (Behavioral Risk Factor Surveillance System) reported that 41.9% of men and 32.9% of women equal to or over the age of 50 said that they had ever had a proctoscopic exam.(2) It is probably true that in addition to the mistaken perception that women are not at risk, individual patients may resent the idea of another uncomfortable, embarrassing test "down there." On the other hand, when women are presented with a proposal for screening on an equal basis with men, they respond in higher numbers.(3) The incredible success of cervical cancer and breast cancer screening attest to the willingness of women to participate in preventive health measures. So our job as physicians is to be sure that women are offered age-appropriate screening for colorectal cancer.
Not that long ago, there was much talk about how the expense of colorectal cancer screening did not justify its widespread use. It's the old preventive health, cost per year of life saved formula. The other stringent criterion, an effect on mortality, had not been proved. This is important in screening because if you simply detect a malignancy, but there is no longevity benefit, what have you done? You just gave the patient a longer time to be stricken with the knowledge that she has cancer. Now, as evidence accumulates, it is apparent that, one by one, colorectal cancer screening measures are proving their worth. First, fecal occult blood testing (FOBT), then the lowly rigid sigmoidoscopy and, soon, I am sure, flexible sigmoidoscopy and colonoscopy will be validated. We already know that these latter procedures "downstage" or "stage shift" colorectal cancer at the time of detection. Thus, a higher percentage of cases detected at screening are in the early, more curable stages, A & B. In a similar way, increased screening with mammography has resulted in the detection of early, as opposed to later stage, breast cancer. This is what we call "secondary prevention" -- you detect a cancer at such an early stage that it is curable.
But colorectal cancer is also amenable to primary prevention -- that is, a measure is taken and the patient never develops cancer. Practically all colorectal cancers develop from benign growths in the colon called adenomatous polyps, or adenomas, that become dysplastic and then malignant. If these growths are detected and removed, cancer will not occur. Some would argue that this is also secondary prevention, since an adenomatous polyp is a premalignant lesion. However, it is not invariably premalignant. It is estimated that about 2.5 per 1000 adenomatous polyps progress to invasive cancer per year and that it takes at least 10 years for an individual polyp to develop into a cancer.(4)
So only a small percentage of adenomatous polyps become malignant. What happens to the rest of them? They may develop stalks and be sloughed off; they may remain stable and not progress; they may regress. It is hard to tell because, ethically, if you find a polyp on screening, you are obliged to remove it. You cannot predict with certainty that it will be one of the ones that will not develop into a cancer. Characteristics that increase the likelihood that malignancy will occur are size (over one centimeter) and dysplastic or villous pathological features.
Polyps and cancers increase in frequency with age, hence the current guidelines advise to start screening at age 50. There are reasons to start screening earlier and more frequently. These are well summarized in the new guidelines published by the American Cancer Society in 1997.(5) Most patients (70-80%) are considered at average risk and should start screening at age 50. The high risk patients, 5-10%, those with inflammatory bowel disease or one of the familial polyposis syndromes, require earlier, more intensive screening and treatment. High-risk patients are usually under specialty care. The moderate-risk patients, 15-20%, are those with a personal or family history of adenomatous polyp or cancer.
How Should You Organize Your Approach to Colon Cancer Screening of the Average and Moderate Risk Patient?
Most of the 56,000 people, half men and half women, who die of colon cancer in this country are in the average or moderate-risk category, and it is really up to the primary care providers to see that age-appropriate screening is offered to all their patients.
We all know that screening millions of people with expensive procedures would result in an enormous medical expense but we also know that the screening rate is very low because:
- the procedures are not offered and
- the patients won't do them. How can you get the most from your time and the medical dollar in approaching CRC screening?
Ask the Family History
Patients with first degree relatives (parent, sibling, child) with colorectal cancer OR adenomatous polyp have an increased risk of getting colorectal cancer.(6),(7) The younger the family member, the higher the risk for your patient at a younger age. It takes 10-15 years for a benign adenomatous polyp to develop into a cancer. Subtract 10 years from the age that the youngest relative was diagnosed and start screening then. Or you can just start screening at age 40. If the relative got the cancer at an older age, over 60, there is probably not much increase in risk and starting screening at age 50 is reasonable.
What Procedures Do You Do?
Let me describe the several alternatives:
FOBT and Flexible Sigmoidoscopy
Start with FOBT (fecal occult blood testing, three-day card). If this test is negative for blood, proceed to a flexible sigmoidoscopy (flex sig). If flex sig is negative, continue screening with an FOBT every year and a flexible sigmoidoscopy every five years.
Rationale: The FOBT is expected to pick up shed blood from a significant lesion particularly in the right or transverse colon. The flexible sigmoidoscopy takes a direct look at the inside of the left colon, preferably up to the splenic flexure, but at least through the sigmoid and part of the descending colon.
If the FOBT is positive: First of all, there is no threshold of positivity. If one window of the card or all six windows show blood, it is positive. This is an automatic signal to go to colonoscopy.
Colonscopy
The colonoscope is sufficiently long to see the lining of the entire colon. If the entire colon was examined and is negative for polyps, a repeat colonoscopy is not considered necessary for 10 years. FOBT is not considered a necessary part of screening going forward. Why? Because we have seen the whole colon, and we know there is no neoplastic lesion there sufficiently large to produce significant bleeding.
Air Contrast Barium Enema (ACBE)
This procedure is less commonly done for screening but is helpful in cases where the scopes cannot be fully inserted into the colon. A frequent reason for this problem is pelvic surgery, commonly ovarian surgery or hysterectomy/oophorectomy in women. The ACBE can easily pick up constricting lesions and large masses but is less sensitive in picking up small mucosal lesions like polyps. Because overlapping segments in the distal colon may preclude a complete exam, a flexible sigmoidoscopy should be added if the lower parts of the bowel are not adequately seen. Every five or ten years is considered an appropriate interval for ACBE for screening.
Insurance Considerations
As Medicare has begun to cover screening procedures, other insurers have followed suit. Now many plans will allow colonoscopy to screen patients with a family history. Detection of blood in the stool requires colonoscopy investigation.
My Personal Favorite Screening Exam
Colonoscopy. It is the most expensive, $1000 and up, but acceptance is high because of sedation, thoroughness in seeing the whole colon and the long screening interval of 10 years if the test is negative. The other advantage is that if polyps are found they can be removed at the same time.
All Colonscopies Are Not Alike
If the preparation is poor or the procedure incomplete, it is not reliable. My recommendation for primary care providers is to identify one or more experienced specialists to do your screening, as well as diagnostic colonoscopy. I also suggest that you get a copy of the procedure note and study it carefully. It should tell you about the adequacy of the prep, what areas were seen or not seen, what was seen and any difficulties encountered. If biopsies were taken, the pathology report should be included. The so-called hyperplastic polyps are not considered risk factors for colorectal cancer. Adenomatous polyps are.
Often a patient will tell you that the procedure was "negative." What they may have understood was that it was negative for cancer. But finding an adenomatous polyp puts them in a different category. They are no longer screening candidates. They require surveillance. Usually, they will be asked to have a follow up procedure in three years.
Getting Down and Dirty with Colorectal Cancer Screening
This section would not be complete without some discussion of the preparation of the colon for screening procedures. The colon has to be clean. It has to be empty of stool, because on the barium enema stool can look like a mass and on flex sig or colonoscopy, you just can't see. For most patients, the prep is the worst part of the whole operation, so you have a responsibility to get it done right, so it doesn't have to be repeated. Ask the patient if they have a problem with constipation or have been told they have diverticulosis. If you get a yes, take some precautionary measures with your prep. The usual prep consists of one or two days of low fiber/clear liquid diet with an electrolyte solution (Golytely® or Colyte®) or laxative the night before and tap water enema or laxative the day of the procedure.
When you put a constipated person on a low fiber diet, they stop having any stools. Everything just stays there. So you need to start low fiber three days before, then clear liquids and a laxative two days before the procedure to empty out the solid waste. The clear liquids and electrolyte prep should remove the opaque intestinal content and tap water enemas, in the morning before the procedure, should assure that the colon is really empty.
Why am I telling you all this? Because women tend to be more constipated than men (don't ask me why) and you have to make sure they get a good prep. Diverticulosis patients have a disordered colon motility, which makes them difficult to prepare too, so a word to the wise...
Put your head together with your colonoscopist and agree on the prep and the variations for patients who may have a problem with it. Get your support staff well oriented to screen for potential problem patients and adjust the advice. This is good advice if you are doing your own flex sig's. You'll have a lot easier time doing these if you have a good prep.
Summary
Colorectal cancer is the second leading cause of cancer death in men and women combined after lung cancer in this country. (Women don't get prostate cancer and few men get breast cancer). Adequate screening and early treatment could significantly reduce the incidence and mortality from colorectal cancer. Few patients are adequately screened. Women are less likely to receive screening than men. Screening is difficult and cumbersome but well worth the physician time and patient effort that it takes.