Re: Cost effectiveness of the NHS breast screening programme: life table model
We thank Dr Zahl for his comments. In estimating the cost of treating over diagnosed breast cancer cases we assumed that any case thought to benefit from adjuvant hormone therapy should not be considered over diagnosis. We accept that this may not always be the case and that some small, slow-growing, estrogen receptor positive tumours may be over diagnosed and treated with adjuvant hormone therapy. As described in the web appendix we included the cost of treating 20 per cent of over diagnosed cases with radiotherapy. Furthermore, as shown in Web figure 6, the cost of treating an over diagnosed case had limited impact on the cost-effectiveness of screening. We only included direct health costs as is common practice for the evaluation of healthcare interventions from the perspective of the UK National Health Service.
We used the estimate for the number of over diagnosed cases from the Independent UK Panel review. We accept that other estimates may differ substantially from this. Indeed we describe this large variation in the web appendix and explicitly model the variation in the probabilistic sensitivity analysis.
Competing interests: No competing interests