Colorectal cancer: the risk factors, symptoms and importance of screening

According to the American Cancer Society, the lifetime risk of developing colorectal cancer is around 1 in 20. But according to a recent report from the Centers for Disease Control and Prevention, there are more than 20 million adults in the US who have never had the recommended screening for the disease, putting them at higher risk of dying from a preventable condition.

Are you aware of the symptoms associated with colorectal cancer? Do you know what you can do to reduce your risk of developing the disease? Are you aware of the current colorectal cancer screening guidelines? Sadly, many us will answer these questions with a “no.”

In line with National Colorectal Cancer Awareness Month this March, we aim to provide answers to all of these questions and find out what more can be done to increase awareness of a condition that is the second leading cause of cancer deaths in the US.

What is colorectal cancer?

Colorectal cancer, also known as bowel cancer, is a cancer that begins either in the colon or the rectum.

The colon is the part of the digestive system that is responsible for reabsorbing fluids and nutrients from undigested food products as they pass through, while the rectum – at the end of the colon – stores feces before they are passed through to the anal canal.

The majority of colorectal cancers start as a polyp – a growth that begins in the inner lining of the colon or rectum. Only certain types of polyps – known as adenomas – can become cancerous.

According to the American Cancer Society, more than 95% of colon and rectal cancers are adenocarcinomas – cancers that begin in the gland cells that line the inside of the colon and rectum.

This year, there are expected to be 96,830 new cases of colon cancer, 40,000 new cases of rectal cancer, and 50,310 deaths from the cancers combined.

But what signs and symptoms indicate the presence of colorectal cancer?

What to look out for

The most common sign of colorectal cancer is rectal bleeding, dark stools or the presence of blood in stools.

Another common sign is a change in bowel habits that lasts more than a few days. This can include diarrhea, constipation or a difference in the consistency of stools.

Cramping or abdominal pain, weakness and fatigue, nausea and vomiting, and unintended weight loss can also indicate the presence of colorectal cancer.

Many of these symptoms can be caused by conditions other than colorectal cancer. But if they persist, it is important to visit a doctor as soon as possible.

Risk factors

Although young adults can develop colorectal cancer, approximately 9 out of 10 people diagnosed with the disease are over the age of 50.

Individuals with a personal history of polyps, and those with a family history of colorectal cancer and other cancers, are at higher risk of developing cancers of the colon or rectum.

A personal history of inflammatory bowel disease (IBD), including ulcerative colitis and Crohn’s disease, can also increase the risk of colorectal cancer.

The consumption of red and processed meat has been associated with an increased risk of colorectal cancer.

Previous studies have also shown that black people have the highest incidence rate of colorectal cancer and the highest mortality related to the condition, compared with all other racial groups in the US. But it is unknown as to why this is.

Although these risk factors cannot be changed, there are some factors than can be modified to reduce colorectal cancer risk.

Smoking is most commonly known to be a cause of lung cancer. But studies have shown that long-term smokers are also more likely to develop and die from colorectal cancer, compared with non-smokers.

Diet can also be a risk factor for the cancer. Last year, Medical News Today reported on a study suggesting that red and processed meat increases the risk of colorectal cancer.

The American Cancer Society states that eating a diet high in fruits, vegetables and whole grains, and low in red and processed meats, may reduce colorectal cancer risk.

Past research has also shown that daily physical activity may reduce colorectal cancer risk by 50%.

But Dr. Richard Wender, chief cancer control officer at the American Cancer Society, says the best way to reduce the risk of colorectal cancer is to undergo regular screening for the condition.

The importance of regular screening

Talking to Medical News Today about the importance of colorectal cancer screening, Dr. Wender said:

“Everyone can reduce their risk of getting this disease or dying from it by being screened according to widely accepted screening guidelines.

Why does this reduce risk? Because the most common finding resulting from screening is a precancerous polyp, not a cancer. If we remove the polyp, we prevent the cancer.”

Current colorectal cancer screening guidelines from the US Preventive Services Task Force recommend that all men and women should have regular screening for the disease from the age of 50 until the age of 75.

Individuals who are at higher risk for the disease, such as those with a family history of colorectal cancer, should be screened from the age of 40 or at 10 years before the age their family member was at diagnosis – whichever is earlier.

The frequency of screening is dependent upon the screening method used.

There are a series of tests available to detect the presence of colorectal cancer.

Tests that can detect both polyps and cancer are:

•          Flexible sigmoidoscopy (recommended every 5 years) – a procedure used to see the inside of the sigmoid colon and the rectum

•          Colonoscopy (recommended every 10 years) – examination of the colon with a camera

•          Double-contrast barium enema (recommended every 5 years) – X-ray of the colon and rectum

•          Computed tomography (CT) colonography/virtual colonoscopy (recommended every 5 years) – detailed pictures of the colon and rectum using a CT scanner.

Tests that mainly find cancer are:

•          Fecal occult blood test – an annual home-based test that detects small amounts of blood in stools. A colonoscopy should be done if this is positive

•          Fecal immunochemical test (FIT) – an annual home-based test that detects small amounts of blood in stools. A colonoscopy should be done if this is positive.

The two tests most commonly used in the US are the FIT and colonoscopy. The American Cancer Society recommends FIT as the best stool testing option.

According to Dr. Wender, any one patient only needs to choose one of these two options – a colonoscopy every 10 years or a FIT every year. But he warned:

“Patients must understand that if the FIT comes back positive for blood then they must have a colonoscopy. A positive FIT that is not followed up by a colonoscopy confers no benefit to the patient at all and should not be considered a completed screen.”

Talking to Medical News Today, Dr. Laura Porter, medical advisor at Colon Cancer Alliance, noted that despite the high incidence of colorectal cancer, it is one of the most treatable forms of cancer. But only if it is found early enough.

She added:

“Colorectal cancer first develops with few, if any, symptoms. It is important not to wait for symptoms before talking to your doctor about getting screened.

Colon cancer is up to 90% treatable when caught early, which means finding it through recommended screening before there are symptoms.”

But it seems that the majority of individuals aged 50 and over are not being screened according to the national guidelines.

Increasing awareness

In November last year, the Centers for Disease Control and Prevention (CDC) released a vital signs report revealing that despite the proven effectiveness of colorectal cancer screening in saving lives, more than 20 million adults over the age of 50 have not undergone screening for the disease.

Although overall incidence of colorectal cancer has declined in recent years, mainly as a result of screening, Dr. Wender said there is no doubt that more needs to be done to raise awareness of the cancer and prompt people into getting screened.

He spoke of the National Colorectal Cancer Roundtable (NCCRT) – a national coalition of public, private and voluntary organizations, including the American Cancer Society, that aims to reduce the incidence of and mortality from colorectal cancer in the US.

Dr. Wender told us that one of the aims of the NCCRT is to achieve 80% colorectal cancer screening rates by 2018. Current screening rates, according to the CDC vital signs report, stand at 65.1%. A campaign to achieve this aim, known as the 80 by 18 campaign, will be officially launched on 17 March at a major press event.

But Dr. Wender says this campaign is just the start.

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