In many adult cancers, at diagnosis, a biopsy of the tumor is done and some of the tumor tissue is sent off for genetic testing. Then, depending on the results of the genetic testing, a particular treatment is chosen by the doctor.
For Osteosarcoma there is only one treatment protocol which has data to show any efficacy and that is the MAP (MUTYH (MYH)-associated polyposis) protocol. Because there is nothing else with good data behind it, there is no treatment reason to do genetic testing and so doctors don’t do it. However, without the data provided by the genetic testing we have no way of changing treatments because we have no data. It’s a chicken and the egg problem, and one we have to solve in order to make advancements in treatment for osteosarcoma. We need genetic bio markers for high risk and low risk patients.
So what is tumor genetic testing? Tumor genetic testing is when a piece of the tumor is sent off for genetic testing. Whole exome testing is best, but a good panel test like Foundation One or IMPACT or GAIN are also really good and very useful.
You want genetic tumor testing which is CLIA (Clinical Laboratory Improvement Amendments) certified because that means that it can be used for treatment decisions (it has met certain quality requirements). And at relapse, you want the option to be able to use a treatment based on genetic testing because there is no standard of care for relapsed osteo, and an identified target on a genetic test might give you an option you would not have had otherwise.
If someone had a germline genetic mutation, it will usually show up in the tumor as well (tumors are heterogeneous so they aren’t consistent all the way through which means the testing doesn’t get everything always). However, tumors always have mutations which only occur in the tumor (they are called somatic mutations) and these mutations can drive the tumor as much or more than anything in the germline.
Some think of the germline mutations as the reason the osteosarcoma originally developed, but the somatic mutations are usually what drives the growth and metastasis of the tumor. At relapse, it may be strongly recommend getting tumor genetic testing done. Nothing may show up and the test results may be useless from a treatment perspective, but if you’ve done it then you know you’ve done everything you could. And even if the data is not helpful for treatment it may be helpful in aggregate for research in something like POWR, the Patient/parent Osteosarcoma genome-Wide Registry.