## Standardization of Body Surface Area Calculations

A report by Thanh Vu, B.Sc. (pharm), Dept. of Pharmacy, Cross Cancer Institute. 1999.

( click here to go to the Body Surface Area BSA calculator )

**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(CCI).Mosteller equationbe use as the standard equation from which all BSA calculations are determined at the Cross Cancer Institute

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 dose^{1}.
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 Bois^{2}
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 George^{3}, 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 calculator^{4}.

This BSA report continues on page 2

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