Impact of Chemotherapy on Colorectal Cancer Screening Results

Colorectal cancer screening?

I recently received a stool collection kit for immunochemical fecal occult blood testing from the health department.
Currently, I am undergoing chemotherapy for breast cancer.
After my first chemotherapy session on January 12, I experienced anal fissures for one to two weeks, during which I had bleeding during bowel movements, and my gums also bled.
I am unsure if this is a side effect of the chemotherapy.
Before my second chemotherapy session on February 9, I asked my attending physician if I could perform the fecal occult blood test, and the doctor advised against it to avoid complications.
However, the symptoms of the anal fissure have improved in the past few days (the blood stains on toilet paper are no longer noticeable).
I would like to know if I can proceed with the screening now that the anal fissure has healed and there is no more bleeding, or should I wait until the entire chemotherapy regimen (four sessions) is completed? My main concern is whether the chemotherapy will affect the test results during this period.
Thank you for your time in responding.

Niming, 50~59 year old female. Ask Date: 2018/02/11

Dr. Ke Fangxu reply Surgery

Indeed, both chemotherapy and anal fissures can affect the results of fecal occult blood tests.
If you have not previously undergone a colonoscopy, it is advisable to schedule one directly; otherwise, you won't know when it is appropriate to conduct screening.
Instead of worrying anxiously, it is better to get the examination done and alleviate your concerns.

Reply Date: 2018/02/11

More Info

Chemotherapy can significantly impact the results of colorectal cancer screening tests, particularly fecal immunochemical tests (FIT) or fecal occult blood tests (FOBT). These tests are designed to detect hidden blood in the stool, which can be a sign of colorectal cancer or other gastrointestinal issues. However, chemotherapy can cause various side effects that may lead to false positives or negatives in these tests.

Firstly, chemotherapy can lead to gastrointestinal side effects such as mucositis, diarrhea, and constipation, which can result in blood in the stool. If you are experiencing rectal fissures or bleeding gums, as you mentioned, these could indeed be side effects of chemotherapy. The presence of blood from these sources can interfere with the accuracy of the fecal blood tests, potentially leading to misleading results. Therefore, it is generally advisable to avoid screening tests during active chemotherapy, especially if you are experiencing symptoms that could cause bleeding.

In your case, since you have experienced rectal bleeding due to fissures, it would be prudent to wait until these symptoms have completely resolved before proceeding with any screening tests. Even if the bleeding has subsided, the residual effects of chemotherapy on your gastrointestinal tract may still affect the test results. Your oncologist's recommendation to postpone the screening was likely made to avoid unnecessary confusion and anxiety that could arise from potentially abnormal test results caused by chemotherapy-related issues.

Once your chemotherapy treatment is completed and you have fully recovered from any side effects, it would be appropriate to undergo colorectal cancer screening. The general recommendation for average-risk individuals is to start screening at age 45, but if you have a family history of colorectal cancer or other risk factors, your healthcare provider may suggest an earlier start.

In summary, while it is essential to stay vigilant about colorectal cancer screening, it is equally important to consider the timing of these tests in relation to your ongoing chemotherapy treatment. Waiting until you have fully recovered from any side effects and have no active bleeding will provide the most accurate results and peace of mind. Always consult with your healthcare provider for personalized advice based on your specific situation and medical history.

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