Standardization of Body Surface Area Calculations
Back to BSA report page 4 of a report by Thanh Vu, B.Sc. (pharm),
( click here to go to the Body Surface Area BSA calculator )
Other methods for dose calculations that do not rely on direct patient monitoring have been developed using Pharmacokinetic (PK) information. The best example of this PK-guided dosage calculation is the formula developed for carboplatin dosage. Since carboplatin is cleared by glomerular filtration, the dose may be calculated using creatinine clearance.
Another non-BSA based dose calculation method that has been proposed is PMT dosing15. This method consists of three compulsory steps in dose calculation: (1) determination of a standard or prime dose for each drug, (2) modifying the prime dose before it is administered according to known factors that will predict the drug-handling ability of an individual (modified dose), and then (3) adjusting the next dose according to the presence or absense of toxicity (toxicity adjusted dose). PMT dosing ensures that the condition of each individual is considered to predict drug effects better. Whether PMT dosing will lead to better standardization of dose effect will require investigation.
In the final analysis, given that the Cross Cancer Institute uses BSA to calculate dosage and the Mosteller equation is the most accurate and user-friendly, it is my recommendation that the CCI adopt this equation as the standard formula from which all chemotherapy dosage should be based. This will alleviate many problems in clinical application and drug trials ultimately providing better care for patients.
Table 1. Five formulas for calculating BSA, ranked according to the RMSE Method of Prediction by Wang et al.
|Boyda||BSA (m2) = Wt(kg)0.4838 * Ht(cm)0.3 * 0.017827|
|Gehan and Georgeb||BSA (m2) = Wt(kg)0.51456 * Ht(cm)0.42246 * 0.02350|
|Mostellerc||BSA (m2) = [ Ht(cm) * Wt(kg) / 3600 ]½
BSA (m2) = [ Ht(in) * Wt(lbs) / 3131 ]½
|Haycockd||BSA (m2) = Wt(kg)0.5378 * Ht(cm)0.3964 * 0.024265|
|Du Bois and Du Boise||BSA (m2) = Wt(kg)0.425 * Ht(cm)0.725 * 0.007184|
a This formula is based on 197 observations. 16,17
b This formula is based on direct measurements of 401 individuals.
c This formula is a simple modification of the equation by Gehan
d This formula is based on measurements of 81 individuals ranging from premature infants to adults.
e This formula is based on measurements of 9 individuals, one of whom was a child.
Table 2. Comparison of various methods and the Mosteller equation in predicting the surface areas (m2) of Thirty-three people.
Table 3. Hypothetical Treatment variations of doxorubicin.
|Dose 1 (mg) of
|Dose 2 (mg) of
Table 3 was produced using the patient data from table 2 and a hypothetical treatment of doxorubicin, requiring a dose of 50mg/m2. Dose 1 uses Nursing’s BSA calculations to calculate the dose. Dose 2 uses the Mosteller formula to calculate the dose.