Body Surface Area – Part I
Posted by Adrienne Choma on Fri, Jun 17, 2011 @ 01:11 PM
Body surface area (or BSA) is a formula used by physicians for determining the amount of drug to administer to a patient when the drug has a narrow therapeutic window (i.e., the amount of the given drug that causes a therapeutic effect is very close to the amount that causes toxic side effects). Chemotherapy drugs fall squarely into this description. BSA is based upon a calculation of an individual patient’s body mass based upon their height and weight.
BSA is a fairly simple albeit imperfect calculation that has endured over the years and today is still regularly applied in the field of oncology. It is quite remarkable that despite the massive investment and significant advances in cancer research, BSA is still the standard of care in dosing chemotherapy drugs. The pharmaceutical industry and medical community has learned much about pharmacokinetics (the study of the impact a body has on an administered drug, i.e., the mechanisms, rate of absorption and distribution of an administered drug), but has not effectively applied this knowledge in advancing cancer drug dosing to meet personal patient needs.
A simple analogy we can all relate to is ten people drink a whole bottle of wine in one sitting. As you can imagine, regardless of their body mass, there will be a wide range of results among these folks - from remaining totally sober to becoming extremely inebriated! The reasons for this interpersonal variation are many, and factors include - if or what they last ate, if they are avid drinkers or not, fitness, age, sex and so on. We all appreciate this variability in individual tolerances – it is not rocket science!
An enduring characteristic of cancer is that everyone’s disease is different and it is well recognized that the best results are achieved when treatment is tailored to the individual. Unfortunately, when doctors dose by BSA they administer the same amount of drug to all patients disregarding interpatient variability of greater than ten-fold that is well established in clinical studies. This means that one patient may have ten times more drug or ten times less drug coursing through their system than the next patient – while the doctor believes that he/she has administered the right dose! It is clear that “one size does not fit all” when administering cancer drugs.
Paul Kenny, European Key Account Manager
Check back next week for Mr. Kenny's Part II blog post on body surface area where he will reveal a better approach for managing chemotherapy drug dosing in patients.