An innovative blood test revealed more of the gene mutations that sustain certain digestive-tract tumors than did a DNA analysis of a traditional tumor biopsy.
The technique is particularly valuable because it can comprehensively detect many different cancer-related mutations from multiple tumors within a single patient, whereas conventional biopsies are able to provide information only on small bits of tumors that are sampled.
Scientists at Dana-Farber Cancer Institute (Boston, MA, USA) collected DNA from tumor samples from as many patients as possible and analyzed them for mutations in the genes v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) and the alpha type platelet-derived growth factor receptor (PDGRA). Blood samples were taken from patients in a clinical trial of a new therapy for gastrointestinal stromal tumor (GIST). GIST is a mutation-driven cancer of the digestive system that arises in approximately 5,000 people in the United States each year.
The blood analysis was performed using a technology known as BEAMing Digital polymerase chain reaction (PCR) Technology, developed by Inostics (Baltimore, MD, USA). This technology expands rare copies of circulating tumor DNA in the bloodstream and has high sensitivity to detect this abnormal genetic material from many tumors in each individual patient.
The investigators compared whether BEAMing technology or traditional tissue analysis was better at picking up secondary drug resistance mutations in the gene for KIT, abnormalities that emerged after the disease had become resistant to certain drugs. The BEAMing technology proved far superior, finding such mutations in 48% of the blood samples, compared to only 12% found in tissue samples using traditional methods. Moreover, nearly half of the blood samples with secondary KIT mutations were found to have several mutations rather than a single mutation.
George Demetri, MD, senior vice president for experimental therapeutics at Dana-Farber, said, "A comprehensive approach to detecting and understanding the impact of different mutations in cancer within each individual patient has before now been impractical, but with this new blood test, we hope to make it easy to integrate it into clinical trials as well as, eventually, into routine clinical practice to make cancer care more precise and personalized to the needs of each patient." The report was presented on April 9, 2013, at a special symposium of the American Association for Cancer Research annual meeting held in Washington DC (USA).