Treating leukemia primarily involves killing the cancerous cells where they originate in the bone marrow. Chemotherapy can knock out bone marrow cells, but it also kills healthy cells, causing such side effects as immunodeficiency and weight loss. Doctors traditionally take a bone marrow biopsy after the treatment to assess how well the drugs have worked. This is unfortunately rather late for those who do not respond to chemotherapy. And even for those who do, the single biopsy is not always representative of how the entire bone marrow is responding.
A PET scan can detect cancerous activity in a full-body image, but it had previously never been used to assess leukemia treatment. As an investigative study, Matt Vanderhoek (mattmv@gmail.com) of the University of Wisconsin and his colleagues imaged eight people with leukemia at different stages of their chemotherapy. They used a PET radio-tracer called FLT (fluoro-L-thymidine), which is readily taken up by cells during cell division. Since leukemia cells divide more than normal cells, they should absorb a lot of FLT and appear brighter in the bone marrow of a PET scan. However, if chemotherapy is able to kill these over-proliferative cells, then the bone marrow should appear dark.
In their sample, the researchers found that brightness and non-uniformity in bone marrow PET scans was an indication that the subject was not responding to the chemotherapy. This assessment, which apparently can be made as early as day one, could potentially spare 30 percent of people with leukemia from a treatment that is wrong for them. -American Institute of Physics
