If you were fated to have lung cancer, a largely incurable disease, or some other deadly form of cancer, would you really want to know? Here are some of the pluses and minuses associated with new testing methods for lung and other kinds of cancer.
Understanding of the human genome has resulted in a profusion diagnostic tests that were unimaginable even 10 years ago. One direct-to-consumer testing company has even developed a blood test to detect tiny segments of cancer cell DNA in blood tests, offering its tests without the need to see a doctor.
The California company, Pathway Genomics, has developed a process it calls "liquid biopsy." Instead of opening up a patient to take a sample of tissue, sending the tissue to the pathology lab to be examined under a microscope, and then making a decision about treatment, the liquid biopsy allows for the detection of cancer before it has even formed tumors. Available in 40 countries, the Cancer Detect system scans blood for extracellular DNA to look for mutations that indicate cancer is in its early stages.
Human cells release bits and pieces DNA when they are destroyed. This process occurs when healthy cells reach the end of their life cycle. It happens when healthy cells are injured or infected and then die. It also occurs at an accelerated rate in tumor cells, which multiply rapidly but also die off rapidly.
Circulating bits and pieces of DNA can act as a kind of "distress signal" to tell the immune system intervention is needed, but the immune system does not always get the message, and it cannot always respond.
Each strand of intact DNA contains three million base pairs. There can be millions of bits and pieces of DNA in a blood sample.The
Pathway Genomics system can detect as few as two cancerous mutations in a sample. Liquid biopsy detects cancer at its very earliest stages when just a few cells are affected, when tumors are too small to be detected any other way.
Who May Benefit From Liquid Biopsy?
The makers of the liquid biopsy testing system point out that their technology is best suited for people who are at higher risk for cancer but who have not yet been told they have the disease. After all, by the time you have a full-grown tumor, you don't need an early detection test. There are a number of reasons someone may be at higher risk of cancer, including:
- History of cancer in the family.
- Known presence of a "cancer gene," such as BRCA1.
- Lifestyle choices, such as smoking.
- Environmental factors, such as exposure to radon, uranium, or radiation.
The liquid biopsy can detect 96 different cancer genes, but it doesn't cover every kind of cancer. It is primarily useful for detecting early stages of ovarian, breast, lung, and colorectal cancers, as well as melanoma.
Even when the test comes back positive, that doesn't mean for sure and certain the tested individual has the cancer.
Gene mutations don't occur in every case of cancer. Almost no mutation is found in more than about 50 percent of cases of a particular kind of cancer. However, a series of gene mutations all related to the same kind of cancer indicate that further action is needed. Individuals can order the tests through their doctors, or on their own accounts with the testing company. Most national health plans don't pay for the test, but some American and Japanese health insurance companies do. The cost is about $300 to $500 a year if you get testing once a year or $700 for one-time-only testing.