Ophthalmology (Eye & Ear Hospital) - Theses
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ItemModeling cost effectiveness of current routine treatments for neovascular age-related macular degeneration from a healthcare payer’s perspective( 2013)Neovascular age-related macular degeneration (nvAMD) is one of the leading causes of blindness in developed countries including Australia, and current gold-standard treatment is with anti-Vascular Endothelial Growth Factor (VEGF) drugs. However, cost-effectiveness (CE) of this treatment has to date only been investigated based on phase III clinical trial data, assessing treatment outcomes in only the study eye over only two years. As effectiveness as well as healthcare use are commonly overestimated in clinical trials, and patients require ongoing treatment beyond the first two years, this approach does not reflect day to day clinical reality. Thus, first the long term effectiveness and healthcare resource use in 200 patients treated with anti-VEGF drugs were assessed with up to 5 years follow-up. Mean treatment duration was 37 (±13) months and mean number of injections were 21(±11;7 in year 1-3, 6 in year 4, 5 in year 5). Visual acuity in the treated eye improved from baseline to last follow-up (49 to 56 letters read (ltrs), p<0.001). Fourty % of patients were treated in both eyes during year 1, and almost 50% by year 4. Treatment costs were highest in the first year (A$18,296 ± 7,991), and lower for uniocular (A$16,123±6,757) than for binocular treatment ($21,487±8,610). Cost decreased to A$11,420 (62%) in year five, with a much steeper decrease in uniocular treatment (to $7,698; 48%). Secondly the importance of using visual acuity (VA) in both eyes in outcomes and utility assessments in eye health were established in a large sample of over 1300 patients and controls. Using the Vision and Quality of Life (VisQOL) multi-attribute utility instrument (MAUI), utility scores decreased significantly with deteriorating vision in both the better and worse eyes when analysed separately. When stratified by 6 health states of vision impairment in both eyes, called vision states, VisQoL utilities decreased as VA declined in the worse eye despite stable VA in the better eye, demonstrating that calculating utilities based only on better eye VA is likely to underestimate the impact of vision impairment and thus treatment alleviating the impairment, particularly when the better eye has no or little VA loss and the worse eye is moderately to severely visually impaired. Thirdly, the CE of anti-VEGF treatment for nv AMD in standard medical practice in Victoria was assessed based on the collected data. In order to demonstrate the necessity of using vision states which capture VA of both eyes rather than modeling by treated or better eye only, several Markov models (MM) were built using TreeAge software, with health transition probabilities based on our real life treatment and utility inputs as described above. Costs and rewards were discounted at 3.5%/year and final results tested in probabilistic sensitivity analyses. Based on the clinical data MMs ran for 5 years, with all treatment assumed to be with ranibizumab (RBZ), the approved drug listed on the Pharmaceutical Benefits Schedule (PBS). The CE ratio was A$15,685/Quality Adjusted Life Year (QALY) for better eye, 16,296/QALY for treated eye and 15,780/QALY for both eye models, with the both eye MM generating the highest amount of QALYs (1.80 compared to 1.74 in MM1 and 1.70 in MM2). Based on these results, all subsequent MM assessing CE were based on vision states rather than treated or better eye only. The overall CE ratio was A$17,900/QALY, under the assumption that all injections were done using RBZ. Assuming that bevacizumab (BVZ, off-label use, not listed on PBS) was used instead of RBZ, the overall CE was A$ 3,196/QALY. Comparing both results for RBZ and BVZ with published CE ratios, all modelled treatment scenarios (both agents) were found to be below commonly applied cut-offs of A$ 30,000 - 70,000/QALY. In conclusion, good long-term effectiveness of anti-VEGF treatment under real life conditions was demonstrated, all relevant costs associated with this treatment were captured, and a novel method to assess the impact of vision impairment and its translation into CE modeling was developed. Based on this, anti-VEGF treatment with both, RBZ and BVZ, was found to be cost-effective over the five year period assessed.