2 The technology
2.1 Enzalutamide (Xtandi, Astellas Pharma) is an oral androgen receptor signalling inhibitor that reduces the proliferation of prostate cancer cells and therefore stops the growth of cancerous tumours. It has a UK marketing authorisation 'for the treatment of adult men with metastatic castrate-resistant prostate cancer whose disease has progressed on or after docetaxel therapy'. The recommended dosage of enzalutamide is 160 mg once daily until disease progression. The summary of product characteristics states that if severe toxicity or an intolerable adverse reaction occurs after taking enzalutamide, treatment should be stopped for 1 week or until symptoms improve, then resumed at the same or a lower dose (120 or 80 mg/day). The dose of enzalutamide should also be reduced if a drug that inhibits CYP2C8 is administered at the same time.
2.2 The summary of product characteristics lists the following common adverse reactions to enzalutamide: headache, hot flushes, falls, bone fractures, hallucinations, anxiety, dry skin, itching, hypertension, low white blood cell count, memory impairment and difficulty thinking clearly. It advises caution when administering enzalutamide to people with a history of seizures or other predisposing factors for seizures, such as underlying brain injury, stroke, brain tumours or brain metastases, or alcoholism. For full details of adverse reactions and contraindications, see the summary of product characteristics.
2.3 Enzalutamide costs £2734.67 for 1 pack of 112 40‑mg capsules, (excluding VAT; 'British national formulary' [BNF] website accessed March 2014). Assuming a daily dose of 160 mg and a mean length of treatment of 8.5 months, the manufacturer estimated that the average cost of treatment with enzalutamide, based on the list price, is £25,269. The manufacturer of enzalutamide has agreed a patient access scheme with the Department of Health. This scheme provides a simple discount to the price listed above, with the discount applied at the point of purchase or invoice. The level of the discount is commercial in confidence. The Department of Health considers that this patient access scheme does not constitute an excessive administrative burden on the NHS.