Adding to the complexity of the patient's response to treatment are differences in how quickly the body activates, breaks down or eliminates specific cancer drugs.
"Many genetic factors likely interact to influence the response of the patient to treatment," Evans said. "That's why the breakthroughs in pharmacogenomics made at St. Jude and elsewhere are so important. They let clinicians identify the patterns of gene activity and inactivity in both the patient's body and in leukemic cells that influence drug efficacy and toxicity. Without such information we would still be treating ALL using a lot of guesswork instead of good science."
Pharmacogenomics is the study of the effects of different genes on the response to drugs. Such studies often include the analysis of the roles of hundreds or even thousands of genes.
Another significant contribution made by St. Jude researchers is the measurement of minimal residual disease (MRD)--the small populations of leukemic cells that survive initial treatment (induction therapy). These cells can replenish the population of leukemic cells and cause the patient to relapse.
Using highly sensitive techniques, St. Jude researchers developed a technique for identifying abnormal combinations of proteins that appear only on the surface of leukemic cells. This allows scientists to quickly and accurately determine the percentage of such cells in samples taken from the patient. Doctors measure MRD to determine if induction therapy has eliminated enough leukemic cells to ensure a high probability of success. Until now, researchers had to rely on the less-accurate technique of microscopic examination to determine which cells in a child's blood sample were leukemic.
"MRD measurements help us to predict the ultimate response of each
Source:St. Jude Children's Research Hospital