Worldwide, bowel cancer kills 694,000 people a year, making it the fourth biggest global cancer killer after lung, liver and stomach cancer. Strikingly, it can be successfully treated in 54% of cases if it is caught early enough.
However, there are barriers to early detection. The Pulse spoke to Dr. Adrian Balasingam, Radiologist and Director and Chairman of Christchurch Radiology Group in New Zealand, about what needs to be done to overcome these, and make colorectal cancer able to be detected earlier and when it is more treatable.
Cancer occurs when cells in a certain part of the body start replicating uncontrollably beyond their normal borders. This leads to the formation of a tumor, which can spread to other parts of the body if it is malignant. If cancer occurs in the bowel, it is called colorectal cancer, or colon cancer for short. The term is applied to cancers that occur in the colon (large intestine) or rectum.
It also happens to be one of the more challenging cancers to diagnose.
“The thing with colorectal cancer is that it often presents in a very non-specific way,” said Dr. Balasingam. “It can present with a series of different symptoms, which can overlap with many other [less serious] diseases. Typical symptoms are: altered bowel habit, bleeding from the bowel, sometimes abdominal pain… but there’s a whole range of different conditions that can present with similar symptoms.”
Most people, when they go to their doctor with abdominal symptoms, have a far less sinister illness than cancer. Nine times out of ten, the symptoms associated with colon cancer are normally caused by something else entirely. “They have these abdominal symptoms which are often very vague,” observed Dr. Balasingam. “The [clinician] will ask, ‘do they have cancer, or do they have a minor temporary condition, which is of no concern?’ And that’s the hard bit for general practitioners in a resource-constrained environment.”
Screening for colon cancer is done by a procedure called a colonoscopy. A colonoscopy is performed by using a long, flexible tube (colonoscope) that is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon. This procedure is invasive, expensive, and time-consuming for both doctors and patients.
Computed Tomography Colonography (CTC), also known as virtual colonoscopy or VC, uses CT to take cross-sectional images of the inside of the bowel to look for polyps or tumors. It uses low-dose radiation CT scanning to obtain an interior view of the colon that would otherwise only be seen with a more invasive colonoscopy.
Sometimes abnormal growths, called polyps, form in the bowel. Over time, these may turn into cancer. Imaging can be used to find colorectal cancer at an early stage, at which point treatment will most likely be successful.
Dr. Balasingam believes virtual colonoscopies using CTC are urgently needed. He said that studies had found CT scans accurate in detecting colorectal polyps and tumors in 90 to 95 percent of cases.
CTC, as well as being less expensive, may be a more acceptable alternative for some patients, due to avoiding use of a colonoscope. The imaging results would help doctors both rule out those patients without cancer and allow those with suspicious findings to be prioritized. What’s more, long waiting lists for diagnostic colonoscopies could also be cut down.
In New Zealand, where Dr. Balasingam practices, colorectal cancer kills more than 1,200 people a year and is the second most common cancer in the country.
A major barrier to the wider use of CTC that Dr. Balasingam pointed out was a lack of understanding from other medical professionals about the utility of the test.
“There’s been a lot of education, which goes a long way towards reassuring people,” he said. “The literature needs to catch up, but more of it is available now. So that’s the biggest barrier right now: getting our clinical colleagues to understand that CT colonography is an extremely effective way to detect colorectal cancer.”