Blood test for cancer

[Spaniel]

I have been told that I can take a blood test to check for colon cancer. If this is possible why would one get a colonoscopy?

[BudRight]

If a physician thinks you have cancer, they're going to get as much data about the tumor as they can in order to make an informed treatment decision. You can also expect several forms of radiography.

[ezzra]

With a colonoscopy, if there are suspicious growth it can biopsied on the spot as well as removing

any growths that showing to be unusual, it is recommended to it for people over 40 years old...

[simple1]

OP: link below should answer any questions you have.

https://www.bowelcanceraustralia.org/about-bowel-cancer

[Sheryl]

This is not correct.

There is something measurable in the blood which is often, but not always, elevated in colon cancer (specifically, CEA). It is also elevated in a number of other conditions.

Because of its poor sensitivity and specificity, it is not recommended as a screening tool. Nonetheless, many private Thai hospitals include it in check-up packages as "cancer screening". The main effect of this will be putting people through a lot of unnecessary scans etc when levels come back high, usually not because of cancer. Meanwhile, it can miss cancers and will certainly miss pre-cancerous polyps, which can be detected and removed on the spot in a colonoscopy.

In addition, CEA levels become elevated only with fairly advanced cancers. It will nto be elevated in an early cancer which of course is what one hopes to catch.