Blood Testing for Optimal Dose Management
Posted by Keith Galloway on Fri, Nov 13, 2009 @ 08:25 AM
To determine the appropriate chemotherapy dose for individual patients, oncologists most often turn to the standard of body surface area (BSA). But relying on BSA alone can result in under-dosing or over-dosing because this standard measurement does not provide enough specific, personalized information about the patient. Individual patients not only absorb and metabolize drugs differently, but the rates of drug absorption and clearance in an individual change day to day, week to week.
Testing of blood drug levels, by contrast, provides the oncologist with more accurate information about how a patient's body is responding to a standard dose. It also gives the physician a tool for monitoring patient response and making any necessary adjustments over time. Blood testing greatly increases the likelihood that the oncologist prescribes the optimal dose and maintains it.
How does such personalized chemotherapy blood testing and management work? At the start of chemotherapy, the oncologist prescribes a test designed to determine the actual blood level of a specific cancer drug in his patient. After a blood draw, the blood sample is sent to a laboratory for analysis. The results, combined with clinical exams, allow the physician to draw conclusions about the efficacy and safety of the initial dose. If the dose is too low or too high, adjustments can be made accordingly.
In a study published in the Journal of Clinical Oncology, a group of metastatic colorectal cancer patients treated with a BSA-based dose of 5-fluorouracil (5-FU) were tested for blood drug levels. The patients received a wide range of dose adjustments in order to reach optimal 5-FU plasma levels during subsequent treatment cycles. The process was repeated over a period of several weeks. Compared with a control group given standard fixed dosing, the dose-adjusted group achieved higher response (33.7 percent versus 18.3 percent) and survival rates (22 months to 16 months).
Blood testing gave oncologists the data they needed to increase dose intensity in the studied patients, thus enhancing efficacy. At the same time, it enabled them to avoid the toxicity that could lead to debilitating side effects. Ninety-four percent of study-group patients received the target dose with dose management. For those patients receiving personalized therapy, the elusive balance between efficacy and safety was achieved.