A closer look at colorectal cancer
Dr Zee Ying Kiat from Parkway Cancer Centre answers commonly-asked questions about one of the most common cancers in Singapore.
What are the trends concerning colorectal cancer among Singaporean men and women?
The frequency with which colorectal cancer is diagnosed increased consistently over the three decades since 1971, although this has reached a plateau since the turn of this century.
A total of 5,383 men and 4,424 women were diagnosed with colorectal cancer from 2011-2015.
Colorectal cancer is second only to lung cancer as a cause of cancer-related death in Singaporean men and third to breast cancer and lung cancer in Singaporean women. However, there has been an increase in the survival rate of people with colorectal cancer over the years.
Who are most at risk of colorectal cancer?
The largest single risk factor is age – the likelihood of developing colorectal cancer increases as one gets older. In particular, this risk increases sharply from the age of 50. In fact, about 90 per cent of cases are diagnosed in people aged 50 or over, compared to 0.5 per cent of cases in people below the age of 30. Men are at slightly higher risk of developing colorectal cancer compared to women.
Individuals with a strong family history of colorectal cancer are at increased risk. A strong family history usually means a person has several relatives diagnosed with bowel cancer, especially if they are in different generations of the family. It can also mean this person has one or more relatives diagnosed at a particularly young age. To have a strong family history, the affected relatives must all come from the same side of one’s family.
People with certain inherited conditions are at increased risk of getting colorectal cancer.
These conditions are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC, also called Lynch syndrome). Genetic changes associated with FAP and HNPCC increase the risk substantially for people who have them, but they are very rare. FAP and HNPCC together are only responsible for about one in 20 cases of colorectal cancer.
Those with colorectal cancer in the past are at increased risk of developing a second colorectal cancer.
Studies have also shown that people who have had lymphoma, testicular cancer or womb (endometrial) cancer have an increased risk of colorectal cancer. This may be due to genetic changes or could be an effect of the treatment for the first cancer.
Persons with growths in the colon, called polyps (or adenomas), are at higher risk of colorectal cancer. Although polyps are not cancerous, they can develop into cancer over a long period of time.
In fact, most colorectal cancers develop from a polyp. Polyps are quite common, with about one in four people having at least one by age 50. However, only a small fraction of polyps develop into cancer – and it takes years to happen.
A polyp that is 1 cm across has roughly a one in six chance of growing into a cancer over 10 years.
Are there lifestyle factors that account for colorectal cancer?
Various studies have linked colorectal cancer to lifestyle factors.
There is a strong and consistent evidence that eating red and processed meat increases colorectal cancer risk. The evidence for a protective effect of fibre has strengthened in the last few years and overall, shows that intake of dietary fibre (particularly from cereals and whole grains) reduces the risk of colorectal cancer.
Obesity is associated with an increased risk of colorectal cancer, particularly for men. Studies have suggested that in comparison to healthy-weight men, overweight men have a 23 per cent higher risk of colorectal cancer, and obese men have a 53 per cent higher risk.
Recent studies have shown that people who are more physically active are at lower risk for colon cancer. Overall, the evidence shows that the most active men can reduce their risk of colorectal cancer by 19-28 per cent in comparison with the least active.
Alcohol intake increases colorectal cancer risk, even at moderate levels of consumption. A published systemic review found a 52 per cent increase in risk for colorectal cancer with a daily intake of three glasses of wine or two pints of beer or above, compared to non-drinkers or occasional drinkers.
Cigarette smoking increases bowel cancer risk. Several studies have found that current or previous smokers have approximately 20 per cent higher risk of colorectal cancer than people who have never smoked. This risk has been reported to increase steadily with the number of cigarettes smoked per day.
What are the ways to prevent colorectal cancer?
It is possible to prevent colorectal cancer.
Regular colorectal cancer screening is one of the most powerful weapons for preventing colorectal cancer. Precancerous polyps can be present, often without symptoms, in the colon for years before invasive cancer develops. Colorectal cancer screening can find precancerous polyps so they can be removed before they turn into cancer. In this way, colorectal cancer is prevented.
Some studies suggest that people may reduce their risk of developing colorectal cancer by increasing physical activity, maintaining a healthy weight, taking more dietary fibre, limiting red and processed meat, limiting alcohol consumption and avoiding tobacco.
What are the prognoses, treatments and success rates for the different stages of colorectal cancer?
An important step following the diagnosis of colorectal cancer is to determine its stage. Cancer stage refers to the extent of a cancer in the body. The staging of colorectal cancer is based on the size of the tumour, whether the lymph nodes contain cancer and whether the cancer has spread from the original site to other parts of the body (e.g. the liver). Stage 1 represents the earliest stage of cancer while Stage 4 represents the most advanced stage, where the cancer has spread to other parts of the body.
Different types of treatment are available for patients with colorectal cancer. Broadly, these treatments are:
The type of treatment recommended will depend on several factors, including the cancer stage and overall health of the patient.
Singapore has seen an overall increasing trend in the survival rate of colorectal cancers over the years. This is largely reflective of the improvements in understanding, preventing and treating colorectal cancer. The earlier colorectal cancer is diagnosed, the better the chance of survival.
Myths & facts
MYTH: Having no symptoms means there is no cancer.
FACT: The truth is that more than half of the people diagnosed with colorectal cancer have no symptoms.
MYTH: Having colorectal cancer means certain death.
FACT: Another common misconception is that colorectal cancer is a diagnosis of death. The truth is that if detected early, the chance of survival from colorectal cancer exceeds 90 per cent. Even in the most advanced cases where the cancer has spread to other parts of the body, breakthroughs in treatment have led to better survival rates.
MYTH: Having a colon polyp means having cancer.
FACT: The truth is that polyps (or adenomas) are benign growths. Polyps do have the potential to develop into cancer over a long period of time, although polyps can be easily removed during an endoscopic examination of the colon, called colonoscopy.
Tags: cancer screening, cancerous polyps, colonoscopy, colorectal cancer, common cancer, history of cancer, misconceptions, obesity and cancer, prevent cancer, reduce cancer risk