Types of colorectal cancer
author/s: Dr Dolores Maluenda Colomer
Types of colorectal cancer
- The majority of colorrectal cancers (75%) are sporadic and appear prompted by environmental or dietetic factors. We can say that in the general population it occurs in a 5% throughout life.
- Between 20 to 25% have a genetic component. In some cases, this means an earlier onset of the tumour in sporadic cases. The risk that a first-grade relative has is greater than that of the rest of the population. Because of this, in those cases, it is mandatory to have information on the familial past history.
- 5% correspond to Lynch´s Syndrome, also called “hereditary non-polypoid colorectal cancer” (HNPCC).
- 1% corresponds to the group called “Familial Adenomatous polyposis” (FAP).
- 1% accounts for patients with “ulcerous colitis”. When the cancer affects the entire colon, after a 10-year disease progression, the risk of a colon cancer appearing is 18 times higher than that of the general population. If the involvement is more limited, the chances are smaller. If the cancer involves the left colon, the chances are 5 times higher than those of the general population and if the cancer involves the right side, the risk is similar to that of the general population.
What is the risk of developing the disease in each group?
- General population: It can appear in a 5% of the general population throughout life.
- With a familial past history, the risk to present the disease increases 2 to 6 times than the normal, increasing as the number of affected relatives increases.
- The early age of a relative at onset is also a predisposing factor for the cancer to appear in earlier ages in other family members.
- And so, colon adenomas diagnosed before the age of 60 in any or some relatives, poses a greater to develop the disease.
RECOMMENDATIONS FOR THE SCREENING OF FAMILIES WITH FAMILIAL ADENOMATOUS POLYPOSIS (FAP). TABLE 1. EXHIBIT 1.
What screening tests should first-grade relatives of an affected individual with familial adenomatous polyposis have?
The best is to see the specialist doctor. (Table 1. Exhibit 1).
Who needs to perform the screening, the tracing or follow up?
The specialist doctor.
How is early diagnosis done? (SECONDARY PROPHYLAXIS).
Early diagnosis consists in identifying affected relatives whom, in turn, present the mutation. In other words, all the first-grade relatives of the individual affected with FAP (positive mutation) will be instructed to undergo genetic testing.
If you have a relative affected with FAP, which relatives should be informed so that they have early diagnosis tests (endoscopies)?
All the relatives of the index case.
If the mutation has been detected in the index case and such mutation is NOT detected in a relative, will this relative need to be followed up afterwards in any special way by a doctor?
The patient will require the same follow up as the general population.
If the genetic study is undetermined in the relative, what should be done next?
A RECTOSIGMOIDOSCOPY once a year from the age of 10-12 to the age of 50. /Table 1. Exhibit 1).
Do all FAP cases have a POSITIVE mutation?
No, only 60% do.
What should the relatives of an individual that has FAP but no mutation do? We are referring to relatives in the 40% group.
First-degree relatives should be seen by a specialist (clinical follow up) and should have an ANNUAL RECTOSIGMOIDOSCOPY from the age of 10-12 onwards until the syndrome appears. When that happens, patients are advised to have a subtotal colectomy with surveillance of the conserved rectal portion, as these patients could have other mutations that are still unknown.
Is a total colonoscopy necessary as part of the annual check up?
No, because 100% of the cases, meaning ALL THE CASES, start to develop polyps in the rectum.