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Treatment of Unruptured Intracranial Aneurysms: Decision and Cost-effectiveness Analysis¹

¹ From the Department of Radiology, Showa General Hospital, Tokyo, Japan (H.T.); Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan (H.T.); and Department of General Medicine and Clinical Epidemiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan (T.N.). Received July 23, 2006; revision requested October 2; revision received October 18; accepted November 21; final version accepted January 8, 2007. Address correspondence to H.T. (e-mail: takaoh-tky{at}umin.ac.jp).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 
Purpose: To prospectively perform a decision and cost-effectiveness analysis of surgical and endovascular treatments of unruptured intracranial aneurysms, with incorporation of the results of the prospective International Study of Unruptured Intracranial Aneurysms.

Materials and Methods: With use of a Markov model, a decision and cost-effectiveness analysis was performed for comparison of surgical or endovascular treatment with no treatment. Twelve clinical scenarios were defined on the basis of aneurysm size and location. Probabilistic sensitivity analyses were performed for 50- and 40-year-old patient cohorts. Treatment was considered to be cost-effective at an incremental cost-effectiveness ratio less than $100 000 per quality-adjusted life-year.

Results: In 50-year-old patients, no treatment was the most cost-effective strategy for aneurysms located in the cavernous carotid artery. For aneurysms smaller than 7 mm located in the anterior circulation, no treatment was the most cost-effective strategy. Endovascular treatment was the most cost-effective option for 7–24-mm aneurysms, whereas surgical treatment was the most cost-effective option for aneurysms 25 mm or larger. For aneurysms smaller than 7 mm or 25 mm or larger located in the posterior circulation, no treatment was the most cost-effective strategy. Surgical treatment was the most cost-effective option for 7–12-mm aneurysms, whereas endovascular treatment was the most cost-effective option for 13–24-mm aneurysms.

Conclusion: For 50-year-old patients, treatment of aneurysms that are small (<7 mm), that are located in the cavernous carotid artery, or that are large (25 mm) and located in the posterior circulation is ineffective or not cost-effective.

© RSNA, 2007

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 
Unruptured intracranial aneurysms affect up to 2%–5% of the population (1). There is still controversy about the management of unruptured intracranial aneurysms (2–4). In 2003, the International Study of Unruptured Intracranial Aneurysms (ISUIA) investigators reported prospective data on the natural history and treatment outcomes of unruptured intracranial aneurysms (5). Aneurysm rupture rates varied depending on aneurysm size and location, and treatment outcomes depended on patient age and aneurysm size and location (5). Researchers in previous decision and cost-effectiveness analyses based their studies on earlier estimates of rupture and complication rates, and these variations in rupture rates and outcome were not considered in their models (6–11). The purpose of our study was to prospectively perform a decision and cost-effectiveness analysis of surgical and endovascular treatments of unruptured intracranial aneurysms, with incorporation of the results of the prospective ISUIA (5).

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 
Study Design
We performed a decision and cost-effectiveness analysis from the societal perspective in which we simulated the clinical paths and health states that patients would traverse after having undergone or not undergone surgical or endovascular treatment for unruptured intracranial aneurysms (Fig 1, Table 1). Although standard practice in cost-effectiveness analysis is to compare each treatment with the next best option, we chose to compare both treatments with no treatment, as our aim in this study was to decide which unruptured intracranial aneurysms should be treated. We chose 50 years as the cohort age because this approximated the average age of treated patients in the ISUIA (5). Aneurysm rupture rates vary depending on aneurysm size and location (5). To account for variable aneurysm characteristics, we modeled 12 different clinical scenarios. We chose the case of a 7–12-mm aneurysm located in the anterior circulation (scenario F [Table 2]) in a 50-year-old woman as the base case.

View larger version (10K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: Markov model of treatment of unruptured intracranial aneurysms. (a) No treatment. (b) Surgical treatment. (c) Endovascular treatment. SAH = sub-arachnoid hemorrhage.

View larger version (9K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: Markov model of treatment of unruptured intracranial aneurysms. (a) No treatment. (b) Surgical treatment. (c) Endovascular treatment. SAH = sub-arachnoid hemorrhage.

View larger version (15K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: Markov model of treatment of unruptured intracranial aneurysms. (a) No treatment. (b) Surgical treatment. (c) Endovascular treatment. SAH = sub-arachnoid hemorrhage.

Markov Model and Its Transition Probabilities
Both authors together designed a Markov model to track a hypothetical cohort of patients until all were dead and placed them into one of five health states: well, well with impaired cognitive status, disabled, disabled with impaired cognitive status, or death (Fig 1). Annual rates of aneurysm rupture and all-cause mortality were applied to the cohort. A no-treatment option does not involve the initial procedure-related risk, but there is an ongoing risk of aneurysm rupture. Treatment of unruptured intracranial aneurysms creates the risk of procedural complications, followed by a reduction in the risk of aneurysm rupture over the remaining lifetime of the patient.

All-cause mortality rates, specific for age and sex, were obtained from U.S. mortality figures for 2002 (12). Age-specific mortality was determined within 10-year categories and after the age of 80 years by means of geometric interpolation and extrapolation, respectively (7). We calculated annual rupture rates of unruptured intracranial aneurysms according to aneurysm size and location from the ISUIA data (5). In the conventional classification scheme, posterior communicating artery aneurysms are grouped with the anterior circulation aneurysms, as they arise from the junction of the internal carotid artery and the posterior communicating artery. In the prospective ISUIA, however, posterior communicating artery aneurysms were grouped with the posterior circulation aneurysms (5). Further corroborative evidence is needed before the hypothesis that posterior communicating artery aneurysms are more dangerous than other anterior circulation aneurysms can be accepted with confidence, as the number of bleeds involved was small (21,22).

We assumed that posterior communicating artery aneurysms had the same rupture rates as other anterior circulation aneurysms (21,22). Case fatality and disability rates for SAH were obtained from a systematic review (13). The rate of cognitive impairment after SAH was calculated from data in a cohort study (14,15). The relative risks of mortality after SAH were obtained from long-term follow-up data about survivors of SAH (16). Treatment outcome of unruptured intracranial aneurysms depends on patient age and aneurysm size and location (5). We calculated poor outcome (morbidity and mortality) rates after surgical and endovascular treatments of unruptured intracranial aneurysms according to patient age and aneurysm size and location from data in the ISUIA (5). The ISUIA did not provide poor outcome rates of surgical (age 50 years) and endovascular (age < 50 years) treatments for 25-mm or larger posterior circulation aneurysms. Therefore, we could not evaluate the cost-effectiveness of surgical or endovascular treatment in these subgroups.

The relative risk of mortality associated with disability due to treatment of unruptured intracranial aneurysms was obtained from long-term follow-up data in patients with disability who had had head trauma (17). SAH from surgically treated unruptured intracranial aneurysms is rare (23). We assumed that surgical treatment provided 100% protection against aneurysm rupture. Long-term efficacy of endovascular treatment of unruptured intracranial aneurysms is not yet known (3). In the ISUIA, a complete obliteration rate of 51% and an incomplete obliteration rate of 21% were reported (5). We assumed that endovascular treatment provided 62% protection against aneurysm rupture.

Costs
The first author (H.T.) obtained costs from the published literature. All direct costs (hospital; physician fees; and outpatient, rehabilitation, and nursing home and home care) were estimated from the societal perspective, in which costs are included regardless of who pays. We obtained costs for surgical and endovascular treatments of unruptured intracranial aneurysms from a previous cost-effectiveness analysis (7), which included costs of follow-up admissions for further treatment. The cost of treating patients with SAH was obtained from a previous cost-effectiveness analysis (7), in which an estimate of 12% out-of-hospital mortality was used and an assumption was made that these patients with SAH accrued no cost. This estimate of out-of-hospital mortality is similar to the out-of-hospital mortality in a meta-analysis (12.4%) (24). We obtained the annual cost of caring for patients with disability from data about long-term care in patients with stroke (18). All costs were calibrated to 2003 U.S. dollars by using the medical component of the consumer price index (25). Both costs and life-years were discounted 3% annually.

Quality of Life
The first author (H.T.) obtained utilities from the published literature. We assigned a utility of 0 to death and a utility of 1 to no disability from treatment of unruptured intracranial aneurysms or SAH. The utility of disability due to treatment or SAH was obtained from a systematic review of utility assessments of patients with stroke (19). We assumed that cognitive impairment caused a 50% reduction in quality of life (6). Quality-of-life adjustments were made for patients undergoing treatment of unruptured intracranial aneurysms and for those with SAH (period, for 3 months) (6,9). We assigned a utility of 0.95 to living with an untreated unruptured intracranial aneurysm, except for living with aneurysms with an annual rupture rate of 0% (9).

Outcome Measurements
Outcome measurements were performed by using software (TreeAge Pro 2006, health care version; TreeAge Software, Williamstown, Mass). We compared surgical or endovascular treatment with no treatment by using an incremental cost-effectiveness ratio (ICER) (26–28). Costs were measured in 2003 U.S. dollars, and incremental effectiveness was measured in quality-adjusted life-years (QALYs) gained. Treatment was considered to be effective at an incremental effectiveness of greater than zero QALY and cost-effective at an ICER of less than $100 000 per QALY (29).

Analyses
The first author (H.T.) performed all analyses by using the health care software mentioned previously. We performed a probabilistic sensitivity analysis, which incorporates all parameter uncertainties into the analysis, by using Monte Carlo simulation with 10 000 iterations for each scenario. This method was used to calculate 95% confidence intervals for incremental costs and QALYs. Next, we performed one-way sensitivity analyses of the data for the base case (scenario F [the case of a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]); these analyses were used to evaluate the impact of each parameter on cost-effectiveness. Finally, we performed probabilistic sensitivity analyses by using Monte Carlo simulation (10 000 iterations) for cohorts with 40-year-old patients.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 
Aneurysm Size and Location
Results of the analysis with 12 scenarios and different combinations of aneurysm size and location (Table 2) indicated that, for aneurysms smaller than 13 mm located in the cavernous carotid artery, both surgical and endovascular treatments were ineffective. For aneurysms of 13 mm or larger, surgical treatment was ineffective. Endovascular treatment was effective but not cost effective. For aneurysms smaller than 7 mm located in the anterior circulation, both treatments were ineffective. For 7–12-mm aneurysms, both treatments were effective. Surgical treatment was not cost effective. Endovascular treatment was cost effective (ICER, $57 700 per QALY). For aneurysms of 13 mm or larger, both treatments were cost effective (ICER, <$15 000 per QALY). For aneurysms smaller than 7 mm located in the posterior circulation, both treatments were effective but not cost effective. For 7–12-mm aneurysms, both treatments were cost effective (ICER, <$7000 per QALY). For 13–24-mm aneurysms, both treatments were effective. Surgical treatment was not cost effective. Endovascular treatment was cost effective (ICER, $67 000 per QALY.) For aneurysms of 25 mm or larger, endovascular treatment was ineffective.

Base Case
Results of one-way sensitivity analysis of the base case (scenario F) showed that four parameters (untreated aneurysm rupture rate, poor outcome rate after treatment, utility [quality of life] of living with an untreated unruptured intracranial aneurysm, and patient age) were most important in the model (Fig 2). The ICERs of surgical and endovascular treatments were less than $100 000 per QALY if the rupture rate was greater than 0.58% per year and 0.32% per year, respectively. The ICERs of surgical and endovascular treatments were less than $100 000 per QALY if the poor outcome rates were less than 10.9% and 8.0%, respectively. The ICERs of surgical and endovascular treatments were less than $100 000 per QALY if the utilities for an untreated aneurysm were less than 0.945 and 0.963, respectively.

View larger version (9K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

View larger version (11K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

View larger version (9K): [in this window] [in a new window] [Download PPT slide]   Figure 2c: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

View larger version (11K): [in this window] [in a new window] [Download PPT slide]   Figure 2d: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

View larger version (7K): [in this window] [in a new window] [Download PPT slide]   Figure 2e: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

View larger version (10K): [in this window] [in a new window] [Download PPT slide]   Figure 2f: One-way sensitivity analysis of the base case (scenario F [a 7–12-mm aneurysm located in the anterior circulation in a 50-year-old woman]). Both treatments were compared with no treatment. (a, b) Surgical treatment (thick solid line) is dominated by no treatment (thin solid line) if rupture rate is less than 0.36% per year. Endovascular treatment (dotted line) is effective within the range. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if rupture rates are greater than 0.58% per year and greater than 0.32% per year, respectively. Arrow corresponds to baseline value (0.53% per year). (c, d) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if poor outcome rates are greater than 13.6% and greater than 10.1%, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if poor outcome rates are less than 10.9% and less than 8.0%, respectively. Arrow and arrowhead correspond to baseline values for surgical and endovascular treatments of 11.5% and 6.5%, respectively. (e, f) Surgical treatment (thick solid line) and endovascular treatment (dotted line) are dominated by no treatment (thin solid line) if the utilities for an untreated aneurysm are greater than 0.966 and greater than 0.979, respectively. ICERs of surgical and endovascular treatments are less than $100 000 per QALY if utilities for an untreated aneurysm are less than 0.945 and less than 0.963, respectively. Arrow corresponds to baseline value (0.95).

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

Several decision and cost-effectiveness analyses of treatment of unruptured intracranial aneurysms have been performed previously (6–11). The studies by Aoki et al (6) and Johnston et al (7) were based on the results of the retrospective ISUIA (30). Other studies were based on earlier estimates of rupture and complication rates (8–11). The studies by Johnston et al (7) and King et al (9) were cost-effectiveness analyses. King et al (9) evaluated the cost-effectiveness of elective surgical treatment of asymptomatic unruptured intracranial aneurysms in 50-year-old patients. They assumed that the annual rupture rate of unruptured intracranial aneurysms was 1%. With the assumption that aneurysms were surgically treated with a morbidity rate of 4.1% and a mortality rate of 1%, elective surgery for asymptomatic unruptured intracranial aneurysms was cost effective (ICER, $24 200 per QALY). They did not consider aneurysm size and location in their model.

Johnston et al (7) performed a cost-utility analysis of surgical and endovascular treatments for unruptured intracranial aneurysms in 50-year-old patients. They assumed that the annual rupture rate for aneurysms smaller than 10 mm was 0.05% and that the rate for aneurysms of 10 mm or larger was 1%. With the assumption that morbidity and mortality rates for surgical treatment were 10.9% and 2.6%, respectively, surgical treatment for aneurysms smaller than 10 mm was ineffective, and surgical treatment for aneurysms of 10 mm or larger was cost effective (ICER, $38 000 per QALY). With the assumption that morbidity and mortality rates for endovascular treatment were 5.3% and 0.4%, respectively, endovascular treatment for aneurysms smaller than 10 mm was ineffective, and endovascular treatment for aneurysms of 10 mm or larger was cost effective (ICER, $10 000 per QALY). These researchers considered aneurysm size (<10 mm, 10 mm) in their model, but they did not consider aneurysm location and treatment outcomes that were based on patient age and aneurysm size and location. Aoki et al (6) performed a decision analysis of surgical treatment of unruptured intracranial aneurysms in 40-year-old patients. They did not consider treatment outcomes that were based on patient age and aneurysm size and location.

There were several limitations in our study. First, we obtained data about two of the most important factors, aneurysm rupture and complication rates, that were used to determine the cost-effectiveness of treatment of unruptured intracranial aneurysms from the ISUIA. Therefore, our findings are dependent on the validity of the ISUIA results.

Second, we assumed that aneurysm rupture rates were constant over time. We calculated annual rates of aneurysm rupture from the 5-year cumulative rupture rates reported in the ISUIA. If aneurysm rupture rates decrease over time, our model would lead to overestimation of the cost-effectiveness of treatment over the lifetime of the patient. Data from prolonged follow-up of untreated patients are needed (5).

Third, in the ISUIA (5), aneurysm rupture rates were determined by using the incidence of SAH or intracerebral hemorrhage. However, cavernous carotid artery aneurysms can cause not only an SAH but also a carotid cavernous fistula. Therefore, our model may have led to an underestimation of the cost-effectiveness of treatment of cavernous carotid artery aneurysms.

Finally, in our study, we compared surgical or endovascular treatment with no treatment although standard practice in a cost-effectiveness analysis is to compare each treatment with the next best option. Both treatments are not always suitable for various unruptured intracranial aneurysms. Because we wanted to determine which unruptured intracranial aneurysms should be treated, we chose to compare both treatments with no treatment.

In conclusion, the results of our study suggest that, for 50-year-old patients, treatment is ineffective or not cost effective for aneurysms that are small (<7 mm), that are located in the cavernous carotid artery, or that are large (25 mm) and located in the posterior circulation. Our results further suggest that, for 40-year-old patients, treatment of aneurysms that are small (<12 mm) or large (25 mm) and located in the cavernous carotid artery or aneurysms that are small (<7 mm) and located in the anterior circulation is ineffective or not cost effective. The benefit was marginal in some cases, with 95% confidence intervals for incremental effectiveness that included zero. Patient preference, symptoms, comorbidities, and life expectancy may be particularly important in making treatment decisions in such instances.

	ADVANCES IN KNOWLEDGE

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 

• For 50-year-old patients, treatment was ineffective or not cost-effective for aneurysms that were small (<7 mm), that were located in the cavernous carotid artery, or that were large (25 mm) and located in the posterior circulation.
  
• For 40-year-old patients, treatment was ineffective or not cost-effective for aneurysms that were small (<12 mm) or large (25 mm) and located in the cavernous carotid artery or aneurysms that were small (<7 mm) and located in the anterior circulation.
  

	IMPLICATIONS FOR PATIENT CARE

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 

• For 50-year-old patients, treatment of aneurysms that are small (<7 mm) will be ineffective or not cost-effective because the risk of rupture is too small.
  
• Treatment of aneurysms that are large (25 mm) and located in the posterior circulation will be ineffective or not cost-effective because the risk of complications from treatment is too high.
  

	FOOTNOTES

 

Abbreviations: ICER = incremental cost-effectiveness ratio • ISUIA = International Study of Unruptured Intracranial Aneurysms • QALY = quality-adjusted life-year • SAH = subarachnoid hemorrhage

Authors stated no financial relationship to disclose.

Author contributions:Guarantor of integrity of entire study, H.T.; study concepts/study design or data acquisition or data analysis/interpretation, H.T., T.N.; manuscript drafting or manuscript revision for important intellectual content, H.T., T.N.; manuscript final version approval, H.T., T.N.; literature research, H.T.; clinical studies, H.T.; experimental studies, H.T.; statistical analysis, H.T.; and manuscript editing, H.T.

	References

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE IMPLICATIONS FOR PATIENT CARE References

 

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