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Ramsay C, Pickard R, Robertson C, et al. Systematic Review and Economic Modelling of the Relative Clinical Benefit and Cost-Effectiveness of Laparoscopic Surgery and Robotic Surgery for Removal of the Prostate in Men with Localised Prostate Cancer. Southampton (UK): NIHR Journals Library; 2012 Nov. (Health Technology Assessment, No. 16.41.)

Cover of Systematic Review and Economic Modelling of the Relative Clinical Benefit and Cost-Effectiveness of Laparoscopic Surgery and Robotic Surgery for Removal of the Prostate in Men with Localised Prostate Cancer

Systematic Review and Economic Modelling of the Relative Clinical Benefit and Cost-Effectiveness of Laparoscopic Surgery and Robotic Surgery for Removal of the Prostate in Men with Localised Prostate Cancer.

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7Discussion

This review sought to answer the following question posed by the UK National Institute for Health Research HTA programme: ‘What is the clinical effectiveness of robotic surgery compared with laparoscopic surgery in the management of localised prostate cancer?’

Summary of findings

This HTA review, using the best available evidence and an appropriately complex health economic model, found that robotic prostatectomy was more effective but more costly than laparoscopic prostatectomy, and predicted that in the UK NHS it may be cost-effective provided that a minimum throughput is achieved for each robotic system and the cost of the system can be minimised. The implications of this review in terms of planning the best care in the NHS for men who require radical prostatectomy for treatment of their localised prostate cancer are therefore substantial, but the uncertainty surrounding our findings, associated with the inadequate evidence base, encourages a cautious approach. At present, of the 5000 men undergoing radical prostatectomy each year in the UK, approximately 50% are operated on using the open technique, 25% using the laparoscopic technique and 25% using the robotic technique.52 With a further five robots being installed in UK NHS hospitals during 2011 to join the 16 already in service, it is likely that the proportion of men undergoing robotic surgery will increase. This review will help inform the setting of criteria, particularly related to monitoring of positive margin rate and minimum throughput, by which these robotic systems should be used to provide most benefit for men with localised prostate cancer and to the NHS. For the future there is an urgent need to standardise recording and reporting of relevant outcomes of treatments for localised prostate cancer within the NHS to allow better analysis of relative effectiveness and modelling of health economic benefits.

Clinical effectiveness

The methodology used in this report makes best use of the current evidence comparing the safety and outcome of radical prostatectomy performed for men with localised prostate cancer by open, laparoscopic or robotic techniques. In the mixed-treatment meta-analysis, only studies that involved a comparator arm were included when estimating differences between treatments. It is noteworthy that none of the studies eligible for inclusion in the meta-analysis comes from a UK centre. The prevalence of radical prostatectomy for localised prostate cancer within a particular community or health-care system is predominantly governed by the prevalence of PSA testing, which continues to be low in the UK relative to other countries with similarly developed health-care systems.35 Although we used uncontrolled data derived from studies performed in many different countries, we did not find any large discrepancies in demographic and disease variables that may have resulted in differences in outcome between UK men undergoing radical prostatectomy and those from other countries. In terms of the surgical teams, most will have undergone mentored training in established laparoscopic and robotic centres elsewhere in Europe or in the USA, with updates from conference and ‘master class’ attendance. Generalisation of our results to the UK context does seem appropriate given this face validity, but a degree of caution needs to be exercised.

As is commonly the case with attempts to summarise outcomes from treatments for prostate cancer, we were unable to identify comparative estimates of cancer survival. Instead, we had to use proxy measures of disease outcome including positive surgical margins and rates of biochemical recurrence at 1 year.74 Although both are considered to be predictive of cancer-specific survival, proof of this relationship is lacking.199,200 Despite these caveats, the findings from the systematic review on differences in the process of care, safety and cancer outcome between robotic and laparoscopic prostatectomy appear to have face validity. The systematic review involved > 19,000 men with an average age of 61 years with preoperative cancer characteristics that were balanced between the groups and consistent with current recommendations for the use of this treatment.43 Overall, 96% of men had cT1–cT2 disease and 94% a Gleason sum score on preoperative biopsy of ≤ 7. Latest data from the British Association of Urological Surgeons (BAUS)201 on 2225 men undergoing radical prostatectomy, submitted by participating institutions in the UK during 2010, suggest that disease characteristics are similar in the UK, with a median age of 60 years, 92% having cT1 or cT2 disease and 93% a preoperative Gleason sum score of ≤ 7. Following surgery, the meta-analysis showed an overall upstaging, with 21% of men in both the laparoscopic and robotic groups being pT3, but no overall worsening of Gleason sum score. The proportion of men having pT3 disease is a key variable because it is predictive of both positive surgical margin rates and ultimate survival. Data from the 60 UK centres contributing to the BAUS 2010 dataset showed that 36% of men undergoing radical prostatectomy had pT3 disease. Additional recent case series from UK centres performing purely laparoscopic or robotic prostatectomy reported pT3 rates of 26% and 46% respectively.156,177 In summary, men included in our study were broadly typical of the population requiring this intervention in the UK NHS, but with a possible lower rate of pT3 disease, reflecting higher use of on-demand PSA testing in the USA and other Western European countries.

Patient-driven outcomes

Safety

Both laparoscopic and robotic radical prostatectomy had a good safety profile, with low rates of major morbidity and only one treatment-related death across all included studies. For most perioperative adverse events the direction of effect was in favour of robotic prostatectomy, suggesting potentially lower rates using the robotic system. The likelihood of this being a real difference was high only for the Clavien IIIb category concerning adverse events that required an additional operative intervention, particularly inadvertent rectal injury. The better vision and instrument dexterity afforded by the robotic system may have contributed to this although it should be noted that the absolute rates were low, increasing the chance that this was a random rather than a systematic difference between the procedures. There was no evidence of any difference in the rate of conversion to an open procedure, even though conversion could occur as an additional risk of machine failure in the case of robotic radical prostatectomy. Although we were unable to assess other relevant patient outcomes such as analgesic requirement, return to full activities or return to employment, given the similarity between these two minimally invasive approaches it is unlikely that there would be any differences.33,202 Overall, our results do suggest that the improved vision and instrument manipulation afforded by the robotic system translates to improved operative patient safety.

Cancer control

All men with localised prostate cancer who embark on radical prostatectomy do so with the expectation that the operation will be curative and save them from the morbidity and early death associated with metastatic disease.203,204 Information that our economic model of longer-term effectiveness could provide on this issue was dependent on estimates of positive margin rates (17.6% for robotic prostatectomy vs 23.6% for laparoscopic prostatectomy) and biochemical recurrence at 1 year (no evidence of a difference), which were the only relevant outcomes obtained from the meta-analysis. Although the evidence was that positive surgical margin rates, a proxy measure for cancer control, may be reduced by the use of robotic radical prostatectomy, the relevance of this in terms of cancer recurrence and long-term efficacy outcomes was unclear. This finding differed from that reported in a previous systematic review,205 which provided no evidence of a statistically significant difference in pooled estimates of surgical margin positivity. Restricting our analysis to low risk of bias studies continued to provide evidence of a lower rate of positive margin rates following robotic prostatectomy but with greater uncertainty and a lower probability that the difference was real. Our conclusion that robotic radical prostatectomy resulted in a lower rate of positive margins should therefore be interpreted with caution given this increased uncertainty around the estimates. In addition, a thorough review by our pathologist expert of the pathology protocols used in included studies showed that they provided limited detail and illustrated technical variation, which may have biased the categorisation of positive margin status and prevented accurate comparison between studies.

We used the best evidence from other literature and help from our expert panel to project, using a mathematical model, these short-term cancer outcome data from our systematic review to estimate long-term cancer-free survival over the subsequent 10 years or the individual's lifetime. The findings suggest that overall survival was higher at 10 years for men undergoing robotic radical prostatectomy than for men undergoing laparoscopic radical prostatectomy, even if the upper CrI limit of the difference in positive margin rates (worse case) was used. In the base case the use of robotic prostatectomy resulted in an average gain of 0.045 life-years. Sensitivity analyses using lower differences in positive margin rates reduced the differences in 10-year overall survival as did increasing the overall biochemical recurrence rate. In all cases the estimates for 10-year survival rates were in the range of 70–80%, in line with those found in previous systematic reviews.41

Long-term adverse events

Although the point estimate for the rate of bladder neck contracture was lower for robotic prostatectomy the degree of uncertainty meant that this was unlikely to represent a true difference. The lack of difference in rates of persistent urinary incontinence (∼6% after either procedure) or persistent erectile dysfunction (∼40% after either procedure) suggests that both techniques provide similar preservation of the key structures of urinary sphincter and neurovascular bundles. It is likely that erectile dysfunction in particular is highly dependent on preoperative sexual activity status and ability to preserve one or both neurovascular bundles at operation rather than on the type of surgery.192,206 The reduced risks of rectal injury and anastomotic leak seen with robotic prostatectomy suggest that a greater accuracy of surgical dissection may be achieved. We do not, however, have sufficient comparative data at present on longer-term continence and sexual function rates to determine whether this translates to improved functional outcomes over the standard laparoscopic technique.

Surgeon outcomes

Uptake of robotic technology among surgeons who undertake radical prostatectomy has generally been enthusiastic, particularly in well-funded health-care systems where detection rates for localised prostate cancer are high. The experience from the USA, where 80,000 men underwent radical prostatectomy in 2007, suggests that if urologists have a choice between practising laparoscopic or robotic procedures most will concentrate on the robotic technique.54 It is unclear how this experience will relate to surgeon preference in countries with lower rates of both use of radical prostatectomy and health-care expenditure. One suggested advantage of the robotic technique is that surgeons may need fewer cases to become fully competent in the procedure as mentoring and learning are facilitated by the console-based surgery.207 Case series with > 200 men were reviewed together with the previously included comparative studies to ascertain possible learning effects and we found some evidence of improved positive margin rates with increasing experience; however, in contrast to previous studies we found no evidence of a differential learning effect for surgeons using laparoscopic or robotic techniques – the same learning curve was identified for both procedures. Part of the reason for this may have been our use of a patient-relevant outcome – positive margin rate – rather than operating time or blood transfusion rates, which are more often used for such comparisons. These data are consistent with the suggestion that it is the individual surgeon's rate of learning that is the dominant factor rather than the technology used.208 The volume of cases was not a confounding factor for the estimation of positive margin rates in the meta-analysis although, as stated above, there was a decrease in positive margin rates with increasing experience when the large case series were included.

Another stated advantage from the surgeon's perspective is the ergonomic advantage of a seated position and scaling of hand movements available with the robotic system, causing less discomfort and a lower risk of chronic cervical pain.209 To some extent this may relate to operating time. We did find that robotic prostatectomy was 15 minutes quicker on average to perform although the different ways of calculating this measure, in particular whether or not the docking time was included for the robotic procedure, give rise to some uncertainty. This saving of time is too small to allow increased productivity but may facilitate a greater rest period for the robotic surgical team.210 Perhaps the most technically taxing part of the operation is achieving a watertight sutured join between the bladder neck and proximal urethral stump that remains patent in the longer term. We did find a significantly lower rate of urine leakage immediately postoperatively in the robotic prostatectomy group, suggesting a more reliable anastomosis, but this did not translate into higher rates of bladder neck contracture. Overall, the evidence that the robotic technology improved surgical operative performance for this particular step of the operation is weak.

Cost-effectiveness

No economic evaluations that compared the alternative forms of surgery from a UK perspective were identified and an economic evaluation based on a discrete-event simulation was planned. As described above, the findings of the systematic review were incorporated into the model and as a consequence the key determinants of cost-effectiveness were the time horizon, differences in positive margin rates and the relative costs of equipment. When a lifetime time horizon was adopted the costs and QALYs for both procedures increased but the increase in QALYs more than compensated for the increase in costs and hence the incremental cost per QALY was < £30,000 for all scenarios considered. This includes a scenario in which the number of procedures performed per year was 50 and in which the most costly robotic equipment was used. The principal reason for this is that adopting a longer time horizon allows more time for any benefits of robotic surgery to accrue and offset the initial higher equipment costs. Caution should, however, be exercised in interpreting the results as they rely on the extrapolation of relatively sparse short-term data within the model. There is uncertainty arising from both the quality of data and the mechanism for extrapolation.

The differences in positive margin rates translated into differences in QALYs and costs. For example, a higher positive margin rate resulted in lower QALYs, a greater need for further treatment and hence higher costs. With respect to costs, the cost per procedure was determined by the acquisition cost of the robotic system (which in turn depended on the specification of the equipment and the payment plan) and the number of procedures that might be performed annually using each robotic system. The costs of acquisition are to a certain degree under the control of a centre and depend on their own specific requirements and negotiations with the manufacturer. The number of procedures performed is a function of clinical need in the population that a centre serves and the population size. The results of the economic evaluation suggest that, when the difference in positive margins is equivalent to the point estimate estimated in the meta-analysis of all included studies, robotic radical prostatectomy was on average associated with an incremental cost per QALY that is less than threshold values typically adopted by the NHS when the cost of acquisition was low or the number of procedures was at the upper end of what could plausibly be achieved under current UK NHS provision (approaching 150 procedures per year).197 This result holds except when the costs of acquisition were at the upper end of those estimated (see Appendix 12). Because the point estimate for difference in positive margin rate was uncertain, sensitivity analysis that progressively changed the difference in rates between robotic and laparoscopic prostatectomy was performed. At more optimistic values (OR = 0.506) the incremental cost per QALY would be less on average than threshold values typically adopted by the NHS when the number of procedures per year approached 100 or the procurement costs were at the lower end of those considered. Not unexpectedly, increasing the OR (OR = 0.955) resulted in a reduction in the QALY gain associated with the use of robotic prostatectomy and an increased cost. With the scenario of an OR for positive margin difference of 0.955 the incremental cost per QALY was only below the threshold if the number of procedures performed using each robotic system was increased to 200 and the lowest procurement cost for robotic equipment was assumed.

The mean estimates of incremental cost per QALY presented, although suggestive that robotic radical prostatectomy could potentially be cost-effective at conventional thresholds compared with laparoscopic prostatectomy, do not fully illustrate the degree of imprecision that exists. In the base-case robotic radical prostatectomy had an approximately 80% chance of being cost-effective when the threshold value for a QALY was £30,000.197 However, caution should be exercised as this result does not incorporate the statistical imprecision surrounding variation in positive margin rates, a key predictor of longer-term outcomes in the model. This indicates the need for further data on the comparative long-term performance of the two forms of surgery. In addition, the sensitivity of estimates from cost-effectiveness for robotic prostatectomy to volume of surgery carried out in each centre argues for careful planning of NHS provision. As an illustration of the current service provision of the 60 UK centres that contributed to the BAUS radical prostatectomy database in 2010, 13 performed > 50 cases per year, of which three performed > 150 cases per year.201 It should be noted, however, that less invasive management options for localised prostate cancer are emerging, including active surveillance, that may slow the growth in use of radical prostatectomy.211

Strengths and weaknesses

Clinical effectiveness

The strength of the study is the systematic approach taken to review the literature. Exhaustive systematic searches were made of the major electronic databases. All potential studies were reviewed for eligibility, including non-English-language publications. The risk of bias for each included study was assessed using the best available tool. To prevent biases caused by selective data extraction all outcome parameters were predetermined by expert panel consensus and any data were extracted using standard forms. Despite these efforts it is possible that some relevant data remained hidden as a result of non-publication.

In total, 54 primary comparative studies were included. Although this haul of relevant studies is impressive, not every study contributed data to each outcome. Furthermore, differences in reporting between studies also limited the opportunities for comprehensive meta-analysis. As a consequence of the limited evidence base, the CIs around many estimates of differences were wide and included differences that would be clinically important but could favour either treatment. Another major limitation resulted from the fact that the majority of comparisons were made against open radical prostatectomy, with few head-to-head comparisons of robotic and laparoscopic technologies. Thus, the estimates generated by the meta-analysis make use of indirect comparisons. The mixed-treatment comparison models used to handle such data are an effective method of handling evidence from many trials on several interventions in one analysis.85 Like all analyses they require assumptions to be made that may or may not be reasonable and accordingly the results should be interpreted with a degree of caution. There were 80 non-randomised comparative studies in which the clinical stage of cancer at baseline was unclear, thereby excluding the studies from the review. Although every effort was made to contact the authors of those papers, only 19 replied. The subsequent finding that exclusion of 18 was appropriate provides some reassurance that these studies do not represent a source of missed useable data but there remains a possibility that some were excluded because of their inadequate reporting.

The review attempted to include only unique data from included studies but we experienced difficulty determining secondary publications because of a lack of clarity in reporting details of treatment centres. There were four study sets (Anastasiadis and colleagues122 and Salomon and colleagues;140 Ficarra and colleagues106 and Fracalanza and colleagues;107 Barocas and colleagues103 and Chan and colleagues;119 Greco and colleagues,129 Jurczok and colleagues131 and Fornara and colleagues127) in which details of the affiliated institute of the first author, type of treatment and treatment dates were similar but it was unclear from the reported text whether or not these studies included an overlap of the same men. It is therefore possible that five studies107,119,127,131,140 have contributed to an overinclusion of men for some perioperative and efficacy outcomes.

The risk of bias assessment in the conduct of a systematic review is important. For this review a robust combined checklist, developed by the Cochrane Collaboration Non-Randomised Studies Methods Group [Barnaby C, Reeves, Jonathan J, Deeks, Julian PT, Higgins, et al. on behalf of the Cochrane Non-Randomised Studies Methods Group. Chapter 13: Including non-randomized studies. In Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 (updated March 2011). The Cochrane Collaboration, 2011. URL: www.cochrane-handbook.org (accessed March 2011)], assessing different sources of bias was produced. A scoring scale approach based on design features was avoided as this has been reported to be inaccurate concerning the direction of bias and can include items that are unrelated to the internal validity of a study.212 For example, the terms ‘prospective study’ and ‘retrospective study’ are particularly ambiguous. ‘Prospective study’ should imply that all design aspects were planned, including hypothesis generation, recruitment of participants, baseline data collection and outcome data collection. In practice, how prospective a study is can often be unclear as some aspects of a study can be prospective, such as hypothesis generation and determination of outcomes, whereas others are retrospective, such as length of stay data collection from hospital records. The potential for bias in designs with different attributes can therefore vary considerably. This systematic review identified few studies at low risk of bias. The moderate inter-rater agreement between the two independent reviewers that was found in our review illustrates that risk of bias can be interpreted in different ways by different people. This is particularly likely in the newly developing methodological area of summarising non-randomised studies in which the level of reporting is often poor.

Many studies failed to report point estimates and measures of variability, hindering their use in estimating weighted mean differences, which require mean estimates for each intervention and standard deviations. It is possible that if means and standard deviations were reported more consistently, effect sizes would be different. However, in the systematic review, when an appropriate measure of variability was not reported for continuous outcomes, consistency across studies reporting the outcome was investigated and this would serve to eliminate biases when determining the direction of effect, even though the magnitude of effect remains uncertain.

A more specific methodological limitation that frustrated pooled analysis was the use of differing definitions and measures of functional outcomes for both urinary and erectile dysfunction. The variety of different ways of measuring dysfunction reduced the ability to compare data or to conduct a comprehensive meta-analysis. This was in part reflected by changing measurement methodologies for dysfunction across the time frame over which the studies were conducted, but it will remain a problem until consensus on important outcome measurements in this clinical area can be agreed. Initiatives such as the UK Medical Research Council-funded Core Outcome Measures in Effectiveness Trials (COMET) initiative213 may be useful in this context. Such initiatives aim to help researchers and clinicians across all specialities to develop a standardised set of outcomes (or core outcomes) that should be measured and reported as a minimum in all clinical trials of a specific condition, in order to make it easier to compare, contrast and synthesise the results of trials, to reduce the risk of inappropriate outcomes being measured and to reduce outcome reporting bias.214

The examination of the influence of learning curves on the results was limited by poor reporting in the included studies. Given the general lack of data reported on the experiences of the centres included in the review, a proxy measure of ‘experience’ was used – namely the number of procedures performed. This measure may be inadequate to detect the differences between the interventions. In addition, when learning curve data were obtained from case series, the reported improvement with increasing experience may have limited applicability to current practice. This is partly because of the early reports of the effects of laparoscopic procedures focusing on refining the technique rather than on the acquisition of the technical skills required to perform the procedure in routine practice. If future studies conform to CONSORT reporting standards for non-pharmaceutical interventions215 this may help to alleviate some of the problems.

In summary, we believe that we have used the best available techniques to identify, review and meta-analyse the data that were available to us. This approach has enabled us to make robust broad conclusions concerning the relative beneficial and adverse effects of robotic prostatectomy compared with laparoscopic prostatectomy but which are associated with a defined degree of uncertainty.

Discrete-event model and economic evaluation

The economic evaluation was based on a discrete-event model. The purpose of this model was not just to estimate relative cost-effectiveness but also to investigate potential differences in clinical outcome between laparoscopic and robotic radical prostatectomy. As the model is a further level of evidence synthesis that builds on the systematic review and meta-analysis, many of the limitations applicable to the clinical data also apply to the economic data.

The decision context, like many of those faced in the evaluation of health-care interventions, was complex. Within a clinical context there is considerable variation between individuals in terms of demographic status and disease progression. In addition, the range, frequency and management of postoperative adverse events following surgery and the variations required in the care pathways necessitated the use of a more complex model than originally envisaged. The model form adopted was able to incorporate the degree of heterogeneity needed to simulate the life trajectory of individuals following surgery. In developing this model, we did not compromise realism in defining how care was implemented in the model. Elements of care that could occur in a given clinical setting were included insofar as they were recognised by the expert panel of practitioners. This inclusive approach effectively led to a complex suite of pathways that could not be modelled using ‘off-the shelf’ modelling packages often used in economic evaluations.

The complexity of the model permitted the simulation of a multitude of possible patient trajectories through the model. This can be illustrated by taking the example of a man who presents with a tumour of stage cT1 and undergoes surgery for presumed localised cancer. On pathological examination of the removed prostate it might be found that the tumour margin is positive but he is counselled to continue under surveillance with regular PSA checks. Happily there is no sign of biochemical recurrence and he remains in the surveillance state until the end of the 10-year time horizon of the study. In a more complex case, a man might remain under surveillance without cancer recurrence but require treatment for urinary dysfunction; he then subsequently requires further treatment for a localised recurrence, which is unfortunately unsuccessful, and he dies of prostate cancer following a period on androgen deprivation therapy. These complexities are required to model the costs and consequences of the differential outcomes of clinical effectiveness found in the systematic review but have the disadvantage of increasing the potential for error and misattribution. To guard against this the longer-term outputs of the model were checked for plausibility and credibility against existing literature sources and the opinions of our expert panel.

The major drivers of model design were heterogeneity in disease status and the requirement to describe realistic care pathways reflecting the range of postoperative adverse events and their treatment. Each health event and postoperative change in management was modelled probabilistically based on available data. As described in Chapter 5 this involved first defining the risk of an event occurring and then, for each man in a simulated cohort, generating a random number between 0 and 1. If the random number was less than the defined risk then the event was assumed to have occurred for that man. This process inevitably led to a large data requirement and a trade-off between model accuracy and data availability.

The data used within the model came from a number of, often independent, sources, which ranged from quantitative data derived from the systematic review through to qualitative data provided by clinical expert members of our advisory panel. Furthermore, parameter estimates for each event were assumed to be unbiased and representative of the population of men requiring radical prostatectomy for localised prostate cancer in the UK NHS. The use of different data sources, although unavoidable, may have introduced biases into the model estimates as the data came from different samples of the worldwide population of men undergoing radical prostatectomy. Furthermore, it was not always possible to assess the likelihood of non-independence in the parameter estimates. To overcome these limitations the parameters estimates were validated by the expert panel and model output discussed within the project team for clinical plausibility.

To address the imprecision we incorporated estimates of uncertainty for some parameters from the results of the meta-analysis. For other parameters we assumed triangular distributions when we had some information on mid-point and upper and lower limits for parameters and then used sensitivity analysis to investigate the behaviour of the model when we varied parameters for which we had only a point estimate and which were crucial to the model output. The sensitivity of health-related and economic outcomes was explored by determining the impact of varying the two parameters perceived to be of crucial importance to overall outcome: rates of pathological positive margin status and incidence of biochemical recurrence. In the case of positive margin rates the parameter was only one of the inputs used for deciding the need for further cancer treatment postoperatively. This precluded the exploration of imprecision in the probabilistic analysis and therefore this parameter was the focus of extensive deterministic sensitivity analysis.

When considering the impacts of each intervention strategy on health states, further treatment for cancer following radical prostatectomy was estimated as a less frequent event following robotic surgery than following laparoscopic surgery. This resulted in fewer cancer-specific deaths following robotic radical prostatectomy than following laparoscopic radical prostatectomy. The consequence of this was greater QALYs following robotic surgery and it also partly compensated for the increased costs of the robotic equipment.

Despite considerable efforts to elicit relevant information it was not possible to precisely quantify the extra cost of the robotic surgery equipment per procedure. This was because there are a plethora of different procurement strategies provided by the manufacturer, Intuitive Surgical, which varied by both method of payment and specification of equipment. Furthermore, the number of procedures performed each period using a given piece of equipment is variable. In the base case we chose to use the highest procurement cost and the highest plausible throughput of 200 cases per year. Repeating the analysis using lower procurement costs and a reduced number of procedures resulted in variation in the proportion of the cost of the robotic system attributed to each procedure, from £3500 to £10,200 (see Table 40). In the base-case analysis, only when the cost was at the higher level determined by a throughput of approximately 150 cases per year was the incremental cost per QALY around £30,000. It should be noted that more favourable assumptions around the positive margin rate tended to reduce the incremental cost per QALY but the incremental cost per QALY would still be > £30,000 for annual throughputs of approximately 100 cases (or a cost of robotic equipment per procedure of approximately £6000). It should also be noted that less favourable but still plausible assumptions concerning the difference in positive margin rates also increased the incremental cost per QALY to > £30,000, particularly when combined with lower throughput of cases. These results indicate that further research is required to more accurately determine positive margin rates and also how they predict long-term cancer outcomes.

In addition to clinical data and costs the model also attempted to incorporate information on the value of different events to the men under treatment – health-state utilities – so that QALYs could be estimated. Searches were conducted to identify data of most relevance to a UK decision-making context but few data were found and not all data were available from a single source. It is possible that we may have misvalued some events, which, if these events occurred at different rates between the two procedures, would have introduced a bias into the analysis. Ideally, health-state utilities data applicable to a UK population should be elicited to overcome this shortcoming.

One aspect of cost not included in the model was the use of unscheduled GP and outpatient visits. There was a lack of data on the frequency of these events with which to model. Previous experience from trials that include men after treatment of prostate cancer would suggest that these costs are relatively modest compared with the cost of surgery. Furthermore, given the apparent lack of difference in effects we did not expect there to be a substantial differential use of these services between groups.

In summary, the discrete-event model attempted to synthesise current clinical practice with the best available estimates of economic and health data to evaluate the potential benefits of robotic prostatectomy in comparison with standard laparoscopic prostatectomy. The model was conservative in that we did not model processes for which we had no evidence of a difference between the two surgical approaches. Furthermore, it did not assume dependence between processes when there was no information available to support a modelled relationship. The model demonstrated that there are circumstances when robotic prostatectomy could be cost-effective as judged against conventional thresholds for willingness to pay for a QALY, especially if lower costs of equipment can be secured and when the surgical capacity is high.

© 2012, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK115710

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