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The war against colorectal cancer

In this month of March, the world celebrates Colorectal Cancer Awareness Month. This campaign was first launched in 1999 in the United States to promote colon cancer screening. Since then, it has been universally celebrated annually in March in several countries of the world.

In the Philippines, the awareness for colorectal cancer (CRC) screening among Filipinos has been increasing in the last few years.

The Medical City, through the initiatives of the gastroenterologists and colorectal surgeons of the Colorectal Clinic, has been leading this campaign in Metro Manila with its symposiums, lay fora and published educational articles for the general public over the years. On a personal note, this life-saving advocacy has been my top priority since I moved back home from the United States in 2014.

Colorectal cancer (involving either the colon or rectum) is the third most common cancer in the world, and the second most common cancer killer affecting both men and women.

Only lung and breast cancer affect more individuals. In the Philippines, the 2015 GLOBOCAN report stated that CRC is the third most common cancer among Filipinos. Breast and lung cancers are more prevalent in the Philippines.

The message remains the same year after year—colorectal cancer screening can save lives. Colorectal cancer is an ideal target for early detection and prevention through screening as it has been shown to reduce cancer risk by as high as 70%.

In the Philippines, the lack of a concrete population-based CRC screening program and the financial burden on the patient are barriers to this campaign. In addition, several local health maintenance organizations (HMOs) still refuse to pay for CRC screening strategies. There is a need to propose a universal screening program for this cancer that is accessible to all Filipinos and applicable in our national setting.

COLORECTAL CANCER IS SCREENABLE

Almost all of these cancers develop over a long period, as most grow slowly and possibly taking around 10 years for some polyps to develop into cancer.

These colonic polyps are abnormal growths in the lining of the large intestine. These can be pre-malignant (pre-cancerous) if these are of the adenomatous and serrated adenomatous types. The risk to cancer in these polyps increases with size, villous architecture, and dysplasia on pathology.

Given the long process of this transformation, screening for and removal of colorectal polyps before these potentially turn into cancer in patients that are at risk can reduce the probability of developing CRC. These polyps and very early cancer usually do not cause symptoms like rectal bleeding, abdominal pain, change in bowel habits, or weight loss. Thus, it is very important to promote CRC screening to the general public.

RISK FACTORS 

Risk factors that predispose an individual to develop colorectal cancer include age, personal history of adenoma or prior CRC, family history of CRC, and pre-existing diseases, like Inflammatory Bowel Disease.

Those aged 50 or more are at a higher risk of getting CRC as 90% of cancers occur after the age of 50. A personal history of colorectal adenomas or prior CRC is another major risk factor.

A family history of a first-degree relative with sporadic CRC increases the risk by two to three-fold. The risk is especially higher when the cancer occurred before the age of 60, or when two relatives have CRC.

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. (See TABLE 1)

When colorectal cancer is suspected, prompt endoscopic examination of the colon should be performed. 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. Patients with advanced cancer may not be surgical candidates and are treated for palliation. The five year-survival rate of persons affected with this cancer at Stage 1 is over 90% when diagnosed early, but less than 15% when diagnosed at Stage 4.

SCREENING METHODS 

In most countries of the world, CRC screening is recommended for people aged 50 years and above, as more than 90% occur over 50. In both genders, subjects aged 50–75 years are the target population for screening.

Earlier CRC screening is advocated in patients with additional risk factors mentioned above. 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.

The two main accepted methods of CRC screening in average-risk individuals recommended by the 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 pre-malignant lesions. Colonoscopy has the benefit of high sensitivity (95%) and specificity. However, it is an invasive test, requires procedural sedation, and has potential to cause harm.

 

As some patients, especially in our country, 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 stool test (Fecal Immunochemical test) 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.

The Fecal Immunochemical test (FIT) has several advantages over the older guaiac-based FOBT (now discontinued in our institution). FIT detects only human globin (protein constituent of human hemoglobin) and is specific for bleeding in the colon.

FIT is reported to have average sensitivity of 79% and a specificity of 94% for CRC. 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.

As a gastroenterologist who advocates colon cancer screening, I encourage opportunistic screening in our clinics and in lay forums. Join us as we celebrate Colorectal Cancer Awareness this month at The Medical City. For inquiries, you may call the Colorectal Clinic at 988-1000/988-7000 Local 7789.

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