This month of March, the world celebrates Colorectal Cancer Awareness Month. Dr. Jun Ruiz, noted gastroenterologist practicing at The Medical City and St. Luke’s Medical Center, and the first Filipino author for the Merck Manual, writes this informative article and shares some insights on how colorectal screening and early detection can be life-saving
Dr. Jun Ruiz is a Diplomate of the American Board of Internal Medicine in Gastroenterology, and a member of the American College of Gastroenterology and American Gastroenterological Association. He finished his Gastroenterology fellowship at the George Washington University in Washington D.C. He has worked at Kaiser Permanente, America’s biggest medical practice, for nine years. He has received numerous awards, including Kaiser Hero Physician and included in the list of America’s Top Gastroenterologists. He is the first and only Filipino author for the Merck Manual, and has written several medical and health articles in international and local peer-reviewed medical journals, newspapers, and magazines.
Dr. Ruiz can be contacted through his email address email@example.com
The world celebrates Colorectal Cancer Awareness Month in March. First launched as an awareness campaign by the Center for Diseases Control and Prevention (CDC) in 1999, this has been successful in promoting colorectal cancer screening. It has been universally celebrated annually in several countries of the world, including the Philippines.
Last year, I initiated this important cancer awareness advocacy at the St. Luke’s Medical Center at Global City. This year, I am collaborating with the Colorectal Unit for this important program at The Medical City in Pasig, Metro-Manila.
Screening can save lives, but not that many people are being screened. Colorectal cancer (CRC) screening has been shown to reduce cancer risk by as high as 70 percent. This campaign has been successful that the screening rate among Americans increased from 50 percent in 2002 to 65 percent in 2012.
In the Philippines, the lack of concrete screening programs and the financial cost for the patient are barriers to this campaign. In addition, several local health maintenance organizations (HMOs) still refuse to pay for CRC screening strategies. As an advocate, I believe that now is the time to educate the general public and mobilize the health community to beat colorectal cancer.
Link of polyps to colorectal cancer
Colorectal cancer is the third most common cancer in the world. Only lung and breast cancers affect more individuals. The Department of Health and the Philippine Cancer Society Registry report in its 2010 Philippine Cancer and Estimates that CRC is the fourth most common cancer among Filipinos. Breast, lung, and liver cancers are more prevalent in the Philippines.
Almost all of these cancers arise over a long period, as most grow slowly and possibly taking around 10 years for some polyps to develop into cancer. The removal of these polyps can reduce the probability of developing CRC in an individual. In addition, polyps and early cancer usually do not cause digestive symptoms.
Colorectal polyps are abnormal growths in the lining of the colon and rectum. These were previously divided into adenomatous polyps and hyperplastic polyps. Adenomatous polyps are pre-cancerous or neoplastic lesions, while hyperplastic polyps have little or no potential to malignancy. The risk to cancer in an adenomatous polyp increases with size, villous architecture, and dysplasia on pathology.
Recently, a new category of polyps called sessile serrated adenomas and its link to colon cancer via another different pathway of colorectal carcinogenesis from that of conventional adenomas has been described. It is believed that sessile serrated adenomas may be the cause of a substantial number of “interval cancers” – i.e. cancers that occur after the baseline examination but before the next scheduled test.
Risk factors for colon cancer
Risk factors that predispose an individual to develop colon and rectal cancer include age, personal history of adenoma or prior CRC, family history of CRC, and pre-existing diseases, like Inflammatory Bowel Disease. Age >50 is the most common risk factor for CRC, as 90 percent of cancers occur after the age of 50.
A family history of a first-degree relative with sporadic CRC increases risk two to three-fold. The risk is especially higher when the cancer occurred before the age of 60, or when two relatives have CRC. The risk of cancer in patients with Inflammatory Bowel Disease (IBD) begins after seven years of disease, and rises about 10 percent per decade.
There are environmental factors identified to contribute to the etiology of CRC, and these include cigarette smoking, alcohol consumption, and obesity. There is a strong association between CRC and a diet that has high saturated fat, low fiber, and high red meat consumption. Though diet might affect the formation of CRC, its exact role remains unclear.
When colon cancer is suspected, prompt endoscopic examination of the colon should be performed. Colonoscopy is the procedure of choice in which a flexible fiberoptic scope is inserted through the anus and rectum and is carefully advanced to visualize the entire length of the colon under conscious sedation (mild anesthesia).
When colon or rectal cancer is documented on a colonoscopy, the patient is referred for surgical resection, as surgery cures early cancer. Concurrent chemotherapy is recommended for patients with advanced disease, especially with lymph node involvement and distant metastases. Radiation therapy is an adjunctive treatment in rectal cancer. Patients with advanced cancer may not be surgical candidates and are treated with palliation.
Importance of CRC screening
Screening an asymptomatic population for CRC is recommended because of the following reasons: 1) CRC is the fourth most common cancer in the Philippines; 2) Removal of polyps during a colonoscopy eliminates their progression to cancer; 3) Early and localized cancer is curable by surgical resection; 4) CRC screening has reduced mortality up to 70 percent; 5) The different methods for screening are cost-effective. All these facts support the campaign for CRC screening in the Philippines.
In several countries of the world, CRC screening is recommended for people aged 50 years and above, as more than 90 percent of cancers occur over 50. In the United States, the US Preventive Services Task Force (USPSTF), American Cancer Society, US Multi-Society Task Force (MSTF) on CRC, American Gastroenterological Association, American College of Gastroenterology (ACG), and Kaiser Permanente (the biggest health maintenance organization in the US) all agree on this recommendation.
The Asia Pacific Consensus Panel on CRC screening concurs with the Western guidelines. In both genders, subjects aged 50 – 75 years are the target population for screening, especially in those regions where the incidence is high.
Screening at an earlier age is advocated in patients with family history of colon cancer, familial polyposis syndromes, and IBD. First-degree relatives of patients with sporadic CRC should undergo screening at the age of 40 or 10 years before the age of the index case, whichever comes first.
Colonoscopy vs. fecal immunochemical test (FIT)
The two main methods of CRC screening in average-risk individuals recommended by different societies are: 1) Colonoscopy every 10 years; 2) Fecal Immunochemical test (FIT) every year.
Colonoscopy is regarded as the gold standard for CRC screening because of its ability to diagnose and potentially remove early lesions. It is a powerful instrument to prevent colon cancer in a person’s lifetime. The American College of Gastroenterology and the National Comprehensive Cancer Network have chosen this as their preferred screening method in all patients. However, it is an invasive test, requires procedural sedation, and has potential to cause harm (bleeding, perforation, respiratory depression), though the rate is very low under expert hands.
As some patients may not want to undergo an invasive test that requires bowel preparation, or may not have access to colonoscopy due to financial constraints or other reasons, the FIT is a very good screening method. By starting with a non-invasive test stool test, the potential for serious harm from an invasive test will be limited to those who have the most to gain from screening. This is where the FIT plays a significant role in population- based screening programs.
The FIT is reported to have sensitivity of 65-85 percent and a specificity of 92 percent for CRC. FIT detects only human globin, and is specific for lower gastrointestinal bleeding. The one widely available here is OC Light Eiken (manufactured by Twin J3). Unlike the prior guaiac-based stool tests, it does not rely on peroxidase activity in human blood that can cross-react to peroxidase present in dietary constituents, such as rare red meat, some cruciferous vegetables and fruits.
Persons who have a positive FIT are 12 to 40 times likely to harbor cancer than those with a negative test. However, there are limitations of fecal-based tests. These must be repeated annually to be effective, as bleeding from cancers or large polyps may be intermittent. If the stool test is positive, a colonoscopy is needed to examine the colon to rule out the presence of cancer or advanced polyps.
Stool DNA test
The stool DNA test (sDNA) was recently approved by FDA last year in the U.S. and may be available here soon. Adenoma and carcinoma cells that contain altered DNA are continuously shed and passed into the feces. This multi-target stool test includes molecular assays for DNA mutations and biomarkers associated with colorectal neoplasia.
“In the Philippines, the lack of concrete screening programs for colorectal cancer and the financial cost for the patient are barriers to this campaign”
The sensitivity of 50-80 percent is limited as it is based on a panel of markers that identify the majority of but not all of CRC. The re-screening interval after a negative test is still uncertain. A recent study published from the New England Journal of Medicine showed a higher sensitivity of sDNA test against FIT, but with a lower specificity. Currently, the American Cancer Society and US MSTF on CRC have concluded that it is an acceptable option for screening for average-risk individuals.
Other less preferred options in CRC screening but not universally recommended by most societies include the prior fecal occult-blood tests (FOBT) that are guaiac-based (low sensitivity), flexible sigmoidoscopy (partial endoscopic examination of the rectum and distal colon), barium enema, and computed tomographic colonography (CTC, virtual colonoscopy).
As a gastroenterologist who advocates colorectal cancer screening, I recommend and encourage a screening colonoscopy in individuals between 50 to 75 years of age who are relatively healthy in whom the benefits of a colonoscopy outweigh the risks associated with the procedure. The patient has to be a reasonable surgical candidate if cancer is found, or when complications from the procedure occur that may require surgery. The patient has to understand that it requires a rigorous bowel preparation, and this method has more risks compared to the other alternative.
Informed and shared-decision making between the patient and the physician should be the crux of the clinic visit. Patient preferences and availability of resources would likely determine the test the patient would eventually choose. Population screening should be accompanied by programs to educate patients and as well as to heighten physician awareness of the concepts and logistics involved in the screening, diagnosis, treatment, and follow up. In the end, CRC screening can just save your life or that of a loved one.
February 2015 Health and Lifestyle