Appropriate Dosing to Optimise Personalised Cancer Treatments

In the pharmacology laboratory, we have developed a method for measuring drug concentrations in animals using dried blood spots (DBS). DBS is a simple method that could be easily carried out by patients at home, using either filter paper-based DBS cards (e.g. Whatman 903, FTA DMPK-C) or small sponges (www.neoteryx.com). The routine use of DBS to clinically test blood was first used in the 1960s as a safe and simple method of testing for inherited metabolic disorders in new born babies. However, in recent years there has been increasing use of DBS to test blood for other things, including for drugs as a way to monitor the drug level in the blood. This method has great potential application in testing blood for drug levels in cancer patients. We wish to establish if this DBS technique is feasible in real-life practice for cancer patients on targeted anti-cancer therapies as should this be the case this innovation could herald a new era in personalised treatment of advanced human cancers allowing doctors to more safely use combinations of targeted therapies. These combinations of targeted therapies have been shown to inhibit development of drug resistance and are increasingly being used in clinical practice. However, targeted therapies often fail (especially combinations of targeted therapies) because of unacceptable toxicities making them intolerable for the patient. With an easy and acceptable method for monitoring the drug level in blood, as could be provided by DBS, the right amount of drug could be given to each individual patient and this 'personalised' drug dosing as standard of care might result in much greater success with combinations of anti-cancer drugs. This drug monitoring is especially important for targeted anti-cancer therapies because many of these (such as Dabrafenib, used for many cases of advanced melanoma) have profound affects on the liver enzymes that metabolise (get rid of) most medications. Dabrafenib is a potent inducer of P450 liver enzymes and this induction means that other drugs metabolised by the same liver pathway (the great majority of drugs are metabolised by the same pathways) will have significantly reduced blood levels if the patient is on Dabrafenib. So it is especially important to be able to monitor blood levels of both Dabrafenib and of other co-medications that the patient may be taking. The DBS sampling method would allow this and would provide a safe, convenient and cheap test that could be conducted in the patient's home and posted back to the laboratory.