## 3 Limitations of BSA Dosing  
A primary limitation of BSA-based dosing is that surface area cannot be measured directly using traditional anthropometric techniques but must be estimated using simple regression formulae. More than 20 of these formulae exist in previous literature, typically based on non-linear functions of simple body measures--body weight and height (Table 1). One of the earliest of these formulae was developed in 1916 by [PERSON] [24] and remains the standard approach used to estimate BSA within current clinical practice. This formula was originally developed based on a sample of eight patients, who were cast in paper moulds to measure their surface area. However, though the [PERSON] formula has been found to have the least errors of all the developed formulae, it has still been described as only providing a rough approximation of BSA [9]. Like the [PERSON] formula, most of the other developed formulae were developed using small, homogenous samples of patients, in terms of their sex, body type and ethnicity. As a result, estimations of BSA calculated using the different formulae can differ by as much as 0.5 m\({}^{2}\) for the same individual and exhibit relative errors from direct measures of BSA, ranging between 9.83% and 43.27% [16]. An example of the differences in estimated BSA values for a typical male patient (height: 164.9 cm, weight: 97.8 kg, body mass index (_BMI_): 36.2 kg/m\({}^{2}\)) are shown in Table 1. The range of BSA values estimated for this individual is 0.41 m\({}^{2}\). Recent studies have suggested that the differences in estimated BSA made by these existing formulae are so great that, in certain cases, they may considerably affect patients' mortality if they are inadvertently underdosed [16]. These errors in BSA estimation are even greater in severely underweight or overweight patients who differ from a \"standard physique\". For example, it has been suggested that the DuBois formula has a systematic negative bias and may be invalid when BSA is below 1.3 m\({}^{2}\). For obese patients (_BMI_) > 30), there is often confusion as to whether actual or ideal body weight should be used to calculate BSA. The choice of which body weight measure to use can be significant since the calculated drug dosage can increase by up to 30% if body weight is used rather than ideal body weight. Without evidence-based recommendations on this issue, practitioners may use either actual or ideal weight or take an average between the two measures. The common practice of either dose banding or rounding of chemotherapy may reduce error when the variation is small from BSA calculation. However, as practice normally allows 5-7% variance with rounding and banding, this will not account for greater inaccuracies [2; 25; 26]. It has long been recognised that the current methods of calculating chemotherapy dosages using estimates of BSA are inaccurate [2; 4] but the development of more effective dose calculation methods for cytotoxic drugs used in anti-cancer treatment, as well as other pharmaceutical agents within other medical fields, is now a research priority. Another issue in using BSA to determine the correct chemotherapy dosage is that several factors cause interpatient variation in drug clearance, including the effects of obesity and variations in body composition, which simple measures of body size--height,