BACKGROUND:In September 2015 the National Institute for Health and Care Excellence published final appraisal documentation recommending idelalisib with rituximab (IR) for the treatment of chronic lymphocytic leukaemia (CLL) in previously treated patients whose disease has relapsed within 24 months and treatment-naïve patients with a 17p deletion or TP53 mutation, based on a simple discount to the list price of idelalisib. OBJECTIVES: Economic analysis in support of the submission for IR in CLL in England and Wales aimed to evaluate the cost-effectiveness of IR in previously-treated patients whose disease has relapsed within 24 months and so are unsuitable for further cytotoxic treatment.

METHODS: A 5-state Markov model was constructed from a National Health Service (NHS) perspective over a lifetime horizon. Study 116 contained 220 patients for whom chemo-immunotherapy was unsuitable owing to poor previous response to such treatment, the presence of 17p deletion or TP53 mutation, or their fitness, randomised 1:1 to IR (intervention) or rituximab with placebo (comparator). Intervention-arm data from Study 116 were used to inform the effectiveness of I+R in terms of response, time on treatment, progression-free and overall survival. Comparator-arm data from Study 116 were used to inform the effectiveness of (i) rituximab monotherapy, and using further assumptions, (ii) ofatumumab monotherapy and (iii) best supportive care (BSC). Utility data and drug, medical resource, adverse event and terminal care costs were obtained from Study 116 EQ-5D surveys, published sources and clinical input. 

RESULTS: Compared to (i) rituximab monotherapy, (ii) ofatumumab monotherapy and (iii) BSC, in patients ineligible for chemo-immunotherapy, the base case ICERs for IR were (i) £26,403, (ii) £10,668 and (iii) £35,275 per QALY gained, respectively and inclusive of a simple price discount. 

CONCLUSIONS: IR was shown to be a highly cost-effective end-of-life therapy in previously-treated patients ineligible for chemo-immunotherapy.