Standardization of Body Surface Area Calculations
Variation between individuals in response to chemotherapy can be of great clinical significance. A successful chemotherapy program should produce a consistent therapeutic effect, while minimizing normal tissue toxicity. Use of a systematic format for reviewing chemotherapy orders reduces the potential for medication errors.
Therefore, it is my recommendation that the Mosteller equation be use as the standard equation from which all BSA calculations are determined at the Cross Cancer Institute (CCI).
Verification of dose is a critical step in chemotherapy administration. BSA determination is essential for chemotherapy dosage calculations. The use of a standardized format for determining BSA is needed to ensure optimal treatment, and can reduce the potential for medication error. Favier, de Cazavove, et al reviewed 2,819 chemotherapy orders and found that 93 (3%) contained at least one error in the dose1. Three of the errors were classified as potentially lethal, including two overdoses of cisplatin and one overdose of doxorubicin.
This systematic approach should include using current weights for body surface area (BSA) calculations, and verifying all dosage calculations. In order to achieve this goal, accurate weights and heights are needed on all orders so that pharmacy can confirm BSA and, ultimately, dose. Verifying BSA and dose are needed to ensure optimal treatment and to prevent chemotherapy underdosing or overdosing. Antineoplastic agents have a lower therapeutic index than most other groups of pharmacological agents. The difference between an underdose and an overdose is small and the consequences can be life-threatening. Therefore, cancer chemotherapy needs a precise and reliable method of determining the BSA and dose. In order to maintain consistency all BSA calculations should be based on the same formula. The Mosteller equation combines both an accurate BSA calculation with ease of use.
Body surface area is a difficult concept to define and is a variable that is extremely difficult to measure reproducibly. Several different formulae for predicting surface area from measurements of height and weight have been derived. In 1916, Du Bois and Du Bois2 examined nine individuals of varying age, shape and size, and measured their BSA directly using molds. From these measurements they derived a formula to estimate BSA using height and weight alone. The Du Bois formula was challened in the 1970's by Gehan and George3, who directly measured the skin-surface area of 401 individuals. They found that the Du Bois formula overestimated BSA by 15% in approximately 15% of cases, but otherwise the original formula was suprisingly accurate considering the small sample size used in its derivation. Even though the Du Bois formula was determined on only nine individuals and certain assumptions were made in developing the formula, it has prevailed and is the most popular nongram for BSA calcuation in current use. More recently, Mosteller produced a simple formula that could be easily remembered and evaluated on a pocket calculator4.