Beyond the type of drug used, other risk factors which may influence the efficacy of scalp cooling include the pharmacokinetic properties of cytostatics, the doses, the number of chemotherapy courses and the admission method. The clinical status of the patient also plays an important role in delaying the metabolism or elimination of the anticancer drug. For example, patients with metastatic disease on the liver may have elevated plasma levels (drug half-life) for a longer period, hence reducing the benefit of scalp cooling. (Satterwhite et al, 1984).

The review by Grevelman and Breed (2005) reported that cooling time seems to influence the success rate of the studies. In the past few years, longer post-infusion cooling times have been used and shown to improve treatment outcome. Success in some studies does not appear to be dose-dependent as was first thought (David & Speechley 1987; Dougherty 2002). The ability to maintain thermal contact over the complete scalp may be more important than dosage (Hunt et al, 1982; Grevelman & Breed, 2005). Therefore the fitting of the cap as well as maintenance of consistent temperature are important factors. These two important criteria are incorporated in the DigniCap™ system, with the provision of a temperature-controlled system and sensor-fitted and tight silicon cap.

Moreover, the experience and motivation of oncology nurses in providing scalp cooling procedures are of paramount in contributing to its success. The efficiency of the treatment can be quite operator-dependant (LeMenager et al, 1997; Ridderhem, 2003; Grevelman & Breed, 2005). In general, the more effective a scalp cooling method is, the higher the motivation, and the more often the cooling caps are applied to patients, the better the results. In addition, there is a need to develop better scalp cooling treatment protocols to ameliorate the discrepancy in results between hospitals.

Perhaps the study conducted by Janssen (2007) best investigated the scalp cooling protocol parameters that can be influenced in scalp cooling. His study was based on a heat-transfer model which investigates the following parameter settings: cooling temperature; the time that scalp cooling is applied, the thermal conductivity of the hair and the thickness of the hair layer. A vital conclusion drawn from this study is that the coolant temperature should be set at –8°C or below to ensure that each patient reaches a low skin temperature of 17°C. If skin temperatures are too high, the coolant temperature should also be adjusted to lower the temperature of the skin to the desired temperature. It is noteworthy to point out that the DigniCap™ system has an optimal coolant temperature of –8°C to –10°C. The coolant temperature is low to reach a cap sensor temperature of around 5°C. While it is not possible to lower the temperature of other scalp cooling machines, the DigniCap™ system has a computerized system that allows easy adjustment of cap temperature down to 2°C on the touch-screen.