Tumor gene mapping has become increasingly important for more precise treatment of cancers; however, a new study suggests that it doesn't go far enough.

Research published in Science Translational Medicine recommends taking gene mapping a step further by also mapping normal DNA of patients, in addition to tumor gene mapping to be able to make better recommendations for treatment.¹ This step may be important to detect mutations in normal cells that also occur in cancerous cells. In short, without the noncancerous sample, the control is missing, only telling half the story.

Researchers at Johns Hopkins University profiled tumors (of 15 tumor types) and normal DNA from 815 patients with advanced cancers. The team tested two methods of analyzing tumor DNA: sequencing all protein-coding genes in a sample, or sequencing a smaller set of 111 genes thought to be cancer-related. The findings were remarkable. Approximately two-thirds of the mutations in the protein-coding genes that were sequenced were also found in the normal cells, making them ineffective therapeutic targets. In the sample targeting the set of 111 genes, the same thing happened; approximately one-third of the mutations in the cancer cells were also found in the normal cells.

The researchers concluded that matched tumor-normal sequencing analyses are essential for precise identification and interpretation of somatic and germline alterations, and have important implications for diagnosing patients and selecting the most effective therapy.

Some research centers, such as Memorial Sloan Kettering Cancer Center (MSKCC), are already performing intensified tumor testing. The new test developed by MSKCC, called MSK-IMPACT, can be used on any type of solid tumor, no matter where in the body the cancer originated, according to MSKCC's blog.² Scientists at MSKCC have also partnered with the biotech company, Foundation Medicine to develop a similar genomic test for blood cancers.

Now that the other half of this important testing is being done, perhaps more testing companies will not rush to profile tumors only, and get the whole picture for more effective treatments for patients.

References:

• Jones S, Anagnostou V, Lytle K, et al. (2015). Personalized genomic analyses for cancer mutation discovery and interpretation. Science Translational Medicine, 7(283).
• Kiesler E. (2015). New Tumor Sequencing Test Will Bring Personalized Treatment Options to More Patients. On Cancer, News and Insights from Memorial Sloan Kettering.