Cancer’s rarity foils screening trials
Dear Dr. Roach: I read with interest your recent column regarding the benefit of a colonoscopy for detecting colon cancer. I am 58 and started experiencing frequent light nausea about two months ago, a few days after getting my first Moderna vaccine. My doctor had me get a blood test. It was generally normal except the liver’s enzyme activity level was very high. That led to a second, liver-focused blood test, an abdominal ultrasound, an abdominal CT scan, followed by a colonoscopy and endoscopy. The last test’s biopsy determined that I have stomach cancer.
If the cancer has spread to the liver, which appears likely, then I have stage IV stomach cancer, which may be fatal. I am not aware of any family history of stomach cancer. Why aren’t endoscopies a recommended test for all age 50+ individuals, as colonoscopies are?
Answer: I am very sorry to hear about your diagnosis, and wish you well with your treatment. The prognosis for stage IV stomach cancer is not good, but recent advances with immunotherapy and chemotherapy should give you hope.
Successful screening for cancer requires two factors: a cancer that is detectable at a time when it can be successfully treated, and a screening test that is safe and accurate at detecting early cancer.
Some cancers are initially very slow-growing. The best examples are cervical and colon cancer, where screening clearly saves lives. They normally grow for five to seven years before they become invasive. This allows screening tests to have a good chance of finding the cancer while it can be cured.
Stomach cancer in a 50-year-old is detectable for an average of about three years before causing symptoms, which makes early detection possible but difficult.
The best-studied screening test for stomach cancer has been an endoscopy, which is relatively invasive and has some potential for harm.
Unfortunately, there are no good trials showing that screening for stomach cancer reduces the likelihood of death, probably because stomach cancer is relatively uncommon in North America, and a successful trial requires many subjects.