The holy grail of cancer treatment is early diagnosis. The earlier a cancer diagnosis is made, the more targeted and less invasive treatments can be. The hope is that fewer people will die from cancer. Many cancers don’t have effective screening tests, including the most aggressive ones like pancreatic and ovarian cancer. We diagnose many cancers once a patient has symptoms. In fact, the only cancers that we regularly screen for are breast, lung, colon, and cervical. Are you surprised? (Keep reading to learn the definition of what a screening test really is.) Ideally, instead of having your family doctor order/perform a mammogram, pap test, CT scan, and colonoscopy, there would be one blood test that could diagnose multiple different cancers. It turns out that there are 18 of these tests either on the market or in development that can detect between 3-12 types of cancer. These tests work by detecting cancer DNA, changes in your own DNA, RNA, or proteins. Sound amazing? Maybe. But wait, there are many things to consider….
- We don’t know if they are able to detect cancers in an earlier stage than we may otherwise find them. Cancer still needs to be fairly advanced to cause changes in the blood that can be detected by these tests. This leads to another limitation –
- If the test comes back negative, does that mean you don’t have cancer or just that you don’t have advanced cancer? If the test comes back positive, yet nothing is seen when you have follow-up imaging studies, then what do we do?
- None of these multi-cancer tests have been studied to see if they decrease the number of people dying from the cancers they are trying to detect.