Genetic Testing – Larry Seymour, MD

genetic testingA few days ago I was sitting in my favorite hospital coffee shop breaking my morning fast (after a test) and heard two people walking by say: “Genes are everything”. Yes, they are, particularly in cancer.

We are all born with about 20,000 genes, and this is our “germ line”. Each gene has its location on the strand of DNA. Genetic testing is used to check this DNA strand for variants which might predispose to cancer as in some kinds of breast cancer. This testing is done with saliva, or a cheek swab or a blood sample. No doubt you’ve seen testing like that on TV.

Genomic testing is done to find the gene changes that have occurred during life due to sun exposure, or tobacco smoke among many factors, some unknown. Most of these changes don’t cause problems, but certainly the two mentioned do. Testing is done the same way.

Genomic profiling tests cancer cells for the DNA changes that have occurred just in the cancer itself. Testing reveals gene abnormalities that cause cancer growth, but it turns out there are many abnormalities in some cancers. This testing is not routinely done for three reasons: 1) It frequently doesn’t give information anyone can act on at this time; 2) It is very expensive (sticker shock is the word); 3) The routine process of testing the cancer in the lab after surgery destroys the DNA in the cancer so this tissue is now not usable for this specialized testing.

This kind of testing is just starting to catch on and in my opinion will be standard in the future in treating most cancers. But to go back to the three reasons for not doing it: Insurance companies say it is not cost effective and sometimes won’t pay for it; (One company -Foundation Medicine- has help for those unable to personally afford the test). You may have seen the ad on TV for OPDIVO, a drug specifically for one of the types of lung cancer. To find out if this lung cancer is the type that responds one needs genomic profiling. There are anecdotal reports of other cancers whose treatment is being changed through genomic profiling.

So, one of the big problems is that if you want to have genomic profiling done, you have to decide to do it BEFORE the surgery is done so that cancer tissue can be specially treated for this purpose. You may have to insist with your oncologist to have it done. Whether the abnormalities it reveals can be matched with a drug is another issue.