A new study in the New England Journal of Medicine traces the evolutionary trees of tumors to find a high degree of genetic heterogeneity and illuminate why even personalized cancer treatment may not be effective, reported Nature. A single biopsy will only provide insight into the mutations in one location; mutations associated with different prognoses or responsive to different treatments may be lurking in other sites, which could explain why tumors often become resistant to therapy after a period of success, according to ScienceNOW.
"We've known for some time that tumors are a patchwork of faults, but this is the first time we've been able to use cutting-edge genome sequencing technology to map out the genetic landscape of a tumor in such exquisite detail," author Charles Swanton, cancer geneticist at Cancer Research UK’s London Research Institute told Reuters.
Swanton and his colleagues traced genome evolution and looked for genetic abnormalities in human kidney tumors. Taking biopsies of one patient’s main tumor in several locations, as well as several metastases the researchers found that only 34 percent of the mutations identified were shared across all of the patient’s samples. Constructing evolutionary trees of two tumors showed that one lineage spawned the patients’ metastases while the main lineage supported the primary tumor, suggesting that treatments based on a biopsy from a primary tumor may not efficiently target metastases. Discovering which mutations are common within a tumor and between tumors could enable a more comprehensive treatment strategy, Swanton told Reuters.