Cancer of the colon and rectum (colorectal cancer) is the
second most common cause of fatal cancer.
If identified early enough, this type of
cancer is curable. Colorectal cancer (CRC) means cancer of the
large intestine or rectum. The commonest symptoms are progressive constipation
and stools mixed with blood. This cancer is best treated in its early stages.
Treatment essentially consists of surgical resection of the colon followed by
repair. If the cancer is very low in the rectum then after surgical removal,
the patient has to live with a permanent colostomy in which the proximal colon
is exteriorized to the left flank and stools are collected in a colostomy bag.
Although colonoscopy is a
sensitive method to detect CRC, since it is time consuming and invasive, it is
less used. More than
half of the Americans aged 50 to 75 years do not comply with the recommended
colorectal cancer (CRC) screening guidelines, which leaves 40 million
A screening test for colorectal cancer (CRC) which is
performed on blood would encourage more patients to undergo screening. If screening and early
detection increases, expensive chemotherapies will be avoided more, resulting
in cost saving to the healthcare system.
In a study conducted in
United States plasma
samples were collected from a number of patients with or without colorectal
cancer. SEPT9 methylated DNA concentration was tested in these specimens.
The results showed that the
improved SEPT9 methylated DNA test was more sensitive than other methods; the
test had an overall sensitivity for CRC of 90% and specificity of 88%,
detecting CRC in patients of all stages of the cancer. For early stage cancer
(I and II), the test was 87% sensitive.
The SEPT9 test
detected CRCs arising from all regions of the colon and rectum, including
proximal tumors arising from the cecum and ascending colon.
a small prospective study, the SEPT9 test detected 12% of adenomas with a
false-positive rate of 3%. The adenoma detection rate was very low with this
test; more than half of the subjects in the study with detectable SEPT9 were
found to possess an adenoma or other polyp by colonoscopy.
Colorectal cancer is best
treated in its early stages; therefore detecting it at an early stage minimizes
the mortality. The
method used for screening is mostly dependent on the patients' choice.
Colonoscopy is less preferred due to its invasiveness and time consuming
procedure. Other tests for CRC screening like fecal testing have reduced due to
their non specificity, sensitivity, and tediousness of stool testing such as
multiple sample submission and handling of the samples. While the SEPT9 methylated
DNA test performs almost comparable to colonoscopy, it is not curative at all
and does not perform well for adenoma detection. Patient compliance for
recommended screening guidelines can be increased by blood-based CRC test in
which blood samples are collected in the primary care setting every two orthree
years. Studies are being carried out to have a better understanding of this
blood-based test and thus encourage individuals in the average risk screening
population to undergo testing of this type.
Reference: Septin 9 methylated
DNA is a sensitive and specific blood test for colorectal cancer; Jorja D
Warren et al; BMC Medicine 2011.