Importance of early detection in colorectal cancer
1. Colorectal cancer is a disease in which early detection is extremely important
Colorectal cancer is increasing globally, but the potential for a cure is known to increase when it is discovered early. For this reason, early detection is important. In colorectal cancer cases, the 5-year survival rate* is known to be higher for patients in which the cancer lesions are localized – i.e., those in which cancer was discovered early – than in patients whose cancer has metastasized. In particular, the 5-year survival rate for early-stage colorectal cancer is 90% or higher, indicating that this is a cancer where the possibility of surviving is extremely high for those diagnosed early.
* 5-year survival rate: Percentage of patients surviving 5 years after being diagnosed with cancer.
Localized: Condition in which colorectal cancer lesions are limited to the colorectal.
Regionally limited: Condition in which colorectal cancer lesions are limited to lymph nodes surrounding the colorectal (sites where white blood cells called lymphocytes aggregate)
Distant metastatis: Condition in which colorectal cancer cells metastasize to the lungs, liver, or other organs, forming lesions
Figure 1 | 5-year survival rate for colorectal cancer by stage of clinical progression. Source: Siegel R, et al. CA Cancer J Clin 2014;64:104-117. c American Cancer Society.
2. How do we find cancer? — Major methods of testing for colorectal cancer —
There are various methods of testing for colorectal cancer, such as the fecal occult blood test (FOBT)* and colonoscopy. Colonoscopy is performed when judgement indicates a positive reaction (bleeding present) in FOBT.
* Testing methods and screening system differ by country or region.
Fecal occult blood test (FOBT)
FOBT is a test by which blood in stool is detected. In the case of colon cancer, the stool may contain blood from the lesion. FOBT is a test in which a stool sample is investigated to determine whether there is any adhering blood in various spots scraped in the sample. Decreases in mortality and disease prevalence are known to be observed when screening for colorectal cancer by FOBT is performed.
Colonoscopy
This is a method of examining the large intestine with a colonoscope. A CCD or other small imaging device at the tip of the colonoscope makes it possible to confirm the status of the intestinal mucosa directly. It is also possible to harvest a sample of tissue that is suspected of being colorectal cancer in a procedure known as a biopsy. By using a microscope or other instrument to perform a pathological examination of this tissue, it is possible to check for the presence of cancer cells and investigate their properties.
3. The importance of cancer screening for early detection
There are a number of countries in the world where cancer prevalence and mortality are both declining. These countries have instituted early detection programs such as colorectal cancer screening, and it is highly possible that efforts such as discovering precancerous tissue referred to as polyps and resecting it early on have been successful.
In these countries, colorectal cancer screening in individuals over the age of 40 or 50 is recommended as a means of reducing colorectal cancer mortality.
This column has been prepared under the supervision of a physician for the purpose of providing general information on cancer.
It is not a substitute for the advice and services that should be provided by a physician or other healthcare professional. If you notice any health conditions, please consult your family doctor or a specialist.
