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Dear Dr. Roach: I read that genetic testing of cancers can lead to exceptional success rates with new therapies that precisely attack cancer for an individual. Should people with a new diagnosis of cancer get this testing? -- R.L.
Answer: The evidence supports genetic testing (next-generation sequencing, or NGS) on some cancers when there are available specific treatments depending on the mutations present in the cancer cells. It also supports testing in people who are healthy enough to consider the available treatments, some of which can be hard on the body's systems.
The evidence is particularly strong for some advanced cancers, specifically lung cancers (adenocarcinoma and large cell carcinoma); prostate cancer; ovarian cancer; cholangiocarcinoma (bile duct cancer); and colorectal cancer. The list of precision-guided treatments is rapidly changing, and there may be times when an expert may recommend NGS on these cancers at an earlier stage or for other cancers (especially thyroid and pancreatic cancer).
We're near the beginning of precision therapy that's based on an individual tumor's susceptibility. With the most recent published data, 10% to 20% of people who undergo NGS will have their treatment changed as a result of testing. However, with more knowledge about specific cancer mutations and new therapies (such as KRAS-directed therapy for pancreatic cancer), I expect a greater benefit from NGS for individuals going forward.
The downsides of NGS are mostly cost but also time. The average cost for NGS can range from $600 to nearly $5,000, depending on the assay and tumor type. The turnaround time to get NGS results back from a tumor is 10-12 days. (This feels like forever when a person has newly diagnosed cancer and wants to know what the treatment will be.) I suspect that as this technology becomes more commonly used, prices will probably fall, and times will be reduced.