Cost-utility of adjuvant hormone therapies for breast cancer in post-menopausal women: sequential tamoxifen-exemestane and upfront anastrozole

Moving beyond the stage: how characteristics at diagnosis dictate treatment and treatment-related quality of life year losses for women with early stage invasive breast cancer

Background:Although evaluations of breast cancer screening programs frequently estimate quality-adjusted life-year (QALY) losses by stage, other breast cancer characteristics influence treatment and vary by mode of detection - i.e. whether the cancer is detected through screening (screen-detected), between screening rounds (interval-detected) or outside screening (community-detected). Here, we estimate the association between early-stage invasive breast cancer (ESIBC) characteristics and treatment-related QALY losses.Methods:Using clinicopathological and treatment information from 675 women managed for ESIBC, we estimated the average five-year treatment-related QALY loss by detection group. We then used regression analysis to estimate the extent to which known cancer characteristics and the detection mode, are associated with treatment and treatment-related QALY losses.Results:Community-detected cancers had the largest QALY loss (0.76 QALYs [95% CI 0.73;0.80]), followed by interval-detected cancers (0.75 QALYs [95% CI 0.68;0.82]) and screen-detected cancers (0.69 QALYs [95%CI 0.67;0.71]). Adverse prognostic factors more common in community-detected and interval-detected breast cancers (large tumours, lymph node involvement, high grade) were largely associated with QALY losses from mastectomies and chemotherapy. Receptor-positive subtypes, more common in screen-detected cancers, were associated with QALY losses related to endocrine therapy.Conclusions:The associations between ESIBC characteristics and treatment-related QALY losses should be considered when evaluating breast cancer screening and treatment strategies.

Cost-utility analyses of drug therapies in breast cancer: a systematic review

The economic evaluation (EE) of health care products has become a necessity. Their quality must be high in order to trust the results and make informed decisions. While cost-utility analyses (CUAs) should be preferred to cost-effectiveness analyses in the oncology area, the quality of breast cancer (BC)-related CUA has been given little attention so far. Thus, firstly, a systematic review of published CUA related to drug therapies for BC, gene expression profiling, and HER2 status testing was performed. Secondly, the quality of selected CUA was assessed and the factors associated with a high-quality CUA identified. The systematic literature search was conducted in PubMed, MEDLINE/EMBASE, and Cochrane to identify published CUA between 2000 and 2014. After screening and data extraction, the quality of each selected CUA was assessed by two independent reviewers, using the checklist proposed by Drummond et al. The analysis of factors associated with a high-quality CUA (defined as a Drummond score ≥7) was performed using a two-step approach. Our systematic review was based on 140 CUAs and showed a wide variety of methodological approaches, including differences in the perspective adopted, the time horizon, measurement of cost and effectiveness, and more specially health-state utility values (HSUVs). The median Drummond score was 7 [range 3-10]. Only one in two of the CUA (n = 74) had a Drummond score ≥7, synonymous of "high quality." The statistically significant predictors of a high-quality CUA were article with "gene expression profiling" topic (p = 0.001), consulting or pharmaceutical company as main location of first author (p = 0.004), and articles with both incremental cost-utility ratio and incremental cost-effectiveness ratio as outcomes of EE (p = 0.02). Our systematic review identified only 140 CUAs published over the past 15 years with one in two of high quality. It showed a wide variety of methodological approaches, especially focused on HSUVs. A critical appraisal of utility values is necessary to better understand one of the main difficulties encountered by authors and propose areas for improvement to increase the quality of CUA. Since the last 5 years, there is a tendency toward an improvement in the quality of these studies, probably coupled with economic context, a better and widely spreading of recommendations and thus appropriation by medical practitioners. That being said, there is an urgent need for mandatory use of European and international recommendations to ensure quality of such approaches and to allow easy comparison.

Cost-utility of adjuvant zoledronic acid in patients with breast cancer and low estrogen levels

BACKGROUND

Adjuvant zoledronic acid (za) appears to improve disease-free survival (dfs) in women with early-stage breast cancer and low levels of estrogen (lle) because of induced or natural menopause. Characterizing the cost-utility (cu) of this therapy could help to determine its role in clinical practice.

METHODS

Using the perspective of the Canadian health care system, we examined the cu of adjuvant endocrine therapy with or without za in women with early-stage endocrine-sensitive breast cancer and lle. A Markov model was used to compute the cumulative costs in Canadian dollars and the quality-adjusted life-years (qalys) gained from each adjuvant strategy, discounted at a rate of 5% annually. The model incorporated the dfs and fracture benefits of adjuvant za. Probabilistic and one-way sensitivity analyses were conducted to examine key model parameters.

RESULTS

Compared with a no-za strategy, adjuvant za in the induced and natural menopause groups was associated with, respectively, $7,825 and $7,789 in incremental costs and 0.46 and 0.34 in qaly gains for cu ratios of $17,007 and $23,093 per qaly gained. In one-way sensitivity analyses, the results were most sensitive to changes in the za dfs benefit. Probabilistic sensitivity analysis suggested a 100% probability of adjuvant za being a cost-effective strategy at a threshold of $100,000 per qaly gained.

CONCLUSIONS

Based on available data, adjuvant za appears to be a cost-effective strategy in women with endocrine-sensitive breast cancer and lle, having cu ratios well below accepted thresholds.

The value-for-money of adjuvant aromatase inhibitors: time to put the debate to rest?

The adoption of costly treatments in public health care systems, such as exists in Canada, must take into account their “clinical benefit to side effect” profiles and “value for money” in an attempt to maximize health gains within current budget constraints [...]

Economic evaluation of hormonal therapies for postmenopausal women with estrogen receptor-positive early breast cancer in Canada

BACKGROUND

Aromatase inhibitor (ai) therapy has been subjected to numerous cost-effectiveness analyses. However, with most ais having reached the end of patent protection and with maturation of the clinical trials data, a re-analysis of ai cost-effectiveness and a consideration of ai use as part of sequential therapy is desirable. Our objective was to assess the cost-effectiveness of the 5-year upfront and sequential tamoxifen (tam) and ai hormonal strategies currently used for treating patients with estrogen receptor (er)-positive early breast cancer.

METHODS

The cost-effectiveness analysis used a Markov model that took a Canadian health system perspective with a lifetime time horizon. The base case involved 65-year-old women with er-positive early breast cancer. Probabilistic sensitivity analyses were used to incorporate parameter uncertainties. An expected-value-of-perfect-information test was performed to identify future research directions. Outcomes were quality-adjusted life-years (qalys) and costs.

RESULTS

The sequential tam-ai strategy was less costly than the other strategies, but less effective than upfront ai and more effective than upfront tam. Upfront ai was more effective and less costly than upfront tam because of less breast cancer recurrence and differences in adverse events. In an exploratory analysis that included a sequential ai-tam strategy, ai-tam dominated based on small numerical differences unlikely to be clinically significant; that strategy was thus not used in the base-case analysis.

CONCLUSIONS

In postmenopausal women with er-positive early breast cancer, strategies using ais appear to provide more benefit than strategies using tam alone. Among the ai-containing strategies, sequential strategies using tam and an ai appear to provide benefits similar to those provided by upfront ai, but at a lower cost.

The impact of structural uncertainty on cost-effectiveness models for adjuvant endocrine breast cancer treatments: the need for disease-specific model standardization and improved guidance

INTRODUCTION

Structural uncertainty relates to differences in model structure and parameterization. For many published health economic analyses in oncology, substantial differences in model structure exist, leading to differences in analysis outcomes and potentially impacting decision-making processes. The objectives of this analysis were (1) to identify differences in model structure and parameterization for cost-effectiveness analyses (CEAs) comparing tamoxifen and anastrazole for adjuvant breast cancer (ABC) treatment; and (2) to quantify the impact of these differences on analysis outcome metrics.

METHODS

The analysis consisted of four steps: (1) review of the literature for identification of eligible CEAs; (2) definition and implementation of a base model structure, which included the core structural components for all identified CEAs; (3) definition and implementation of changes or additions in the base model structure or parameterization; and (4) quantification of the impact of changes in model structure or parameterizations on the analysis outcome metrics life-years gained (LYG), incremental costs (IC) and the incremental cost-effectiveness ratio (ICER).

RESULTS

Eleven CEA analyses comparing anastrazole and tamoxifen as ABC treatment were identified. The base model consisted of the following health states: (1) on treatment; (2) off treatment; (3) local recurrence; (4) metastatic disease; (5) death due to breast cancer; and (6) death due to other causes. The base model estimates of anastrazole versus tamoxifen for the LYG, IC and ICER were 0.263 years, €3,647 and €13,868/LYG, respectively. In the published models that were evaluated, differences in model structure included the addition of different recurrence health states, and associated transition rates were identified. Differences in parameterization were related to the incidences of recurrence, local recurrence to metastatic disease, and metastatic disease to death. The separate impact of these model components on the LYG ranged from 0.207 to 0.356 years, while incremental costs ranged from €3,490 to €3,714 and ICERs ranged from €9,804/LYG to €17,966/LYG. When we re-analyzed the published CEAs in our framework by including their respective model properties, the LYG ranged from 0.207 to 0.383 years, IC ranged from €3,556 to €3,731 and ICERs ranged from €9,683/LYG to €17,570/LYG.

CONCLUSION

Differences in model structure and parameterization lead to substantial differences in analysis outcome metrics. This analysis supports the need for more guidance regarding structural uncertainty and the use of standardized disease-specific models for health economic analyses of adjuvant endocrine breast cancer therapies. The developed approach in the current analysis could potentially serve as a template for further evaluations of structural uncertainty and development of disease-specific models.

A systematic review and methodological evaluation of published cost-effectiveness analyses of aromatase inhibitors versus tamoxifen in early stage breast cancer

BACKGROUND

A key priority in developing policies for providing affordable cancer care is measuring the value for money of new therapies using cost-effectiveness analyses (CEAs). For CEA to be useful it should focus on relevant outcomes and include thorough investigation of uncertainty. Randomized controlled trials (RCTs) of five years of aromatase inhibitors (AI) versus five years of tamoxifen in the treatment of post-menopausal women with early stage breast cancer, show benefit of AI in terms of disease free survival (DFS) but not overall survival (OS) and indicate higher risk of fracture with AI. Policy-relevant CEA of AI versus tamoxifen should focus on OS and include analysis of uncertainty over key assumptions.

METHODS

We conducted a systematic review of published CEAs comparing an AI to tamoxifen. We searched Ovid MEDLINE, EMBASE, PsychINFO, and the Cochrane Database of Systematic Reviews without language restrictions. We selected CEAs with outcomes expressed as cost per life year or cost per quality adjusted life year (QALY). We assessed quality using the Neumann checklist. Using structured forms two abstractors collected descriptive information, sources of data, baseline assumptions on effectiveness and adverse events, and recorded approaches to assessing parameter uncertainty, methodological uncertainty, and structural uncertainty.

RESULTS

We identified 1,622 citations and 18 studies met inclusion criteria. All CE estimates assumed a survival benefit for aromatase inhibitors. Twelve studies performed sensitivity analysis on the risk of adverse events and 7 assumed no additional mortality risk with any adverse event. Sub-group analysis was limited; 6 studies examined older women, 2 examined women with low recurrence risk, and 1 examined women with multiple comorbidities.

CONCLUSION

Published CEAs comparing AIs to tamoxifen assumed an OS benefit though none has been shown in RCTs, leading to an overestimate of the cost-effectiveness of AIs. Results of these CEA analyses may be suboptimal for guiding policy.

Cost-utility of the 21-gene recurrence score assay in node-negative and node-positive breast cancer

The 21-gene recurrence score (Oncotype DX: RS) appears to augment clinico-pathologic prognostication and is predictive of adjuvant chemotherapy benefit in node-negative (N-) and node-positive (N+), endocrine-sensitive breast cancer. RS is a costly assay that is associated with good 'value for money' in N- disease, while economic evaluations in N+ disease based on most recent data have not been conducted. We examined the cost-utility (CU) of a RS-guided adjuvant strategy, compared to current practice without RS in N- and N+, endocrine-sensitive, breast cancer from a Canadian health care system perspective. A generic state-transition model was developed to compute cumulative costs and quality-adjusted life years (QALYs) over a 25-year horizon. Patient outcomes with and without chemotherapy in RS-untested cohorts and in those with low, intermediate and high RS were examined based on the reported prognostic and predictive impact of RS in N- and N+ disease. Chemotherapy utilization (current vs. RS-guided), unit costs and utilities were derived from a Nova Scotia Canadian population-based cohort, local unit costs and the literature. Costs and outcomes were discounted at 3% annually, and costs were reported in 2011 Canadian dollars ($). Probabilistic and one-way sensitivity analyses were conducted for key model parameters. Compared to a non-RS-guided strategy, RS-guided adjuvant therapy was associated with $2,585 and $864 incremental costs, 0.27 and 0.06 QALY gains, and resultant CUs of $9,591 and $14,844 per QALY gained for N- and N+ disease, respectively. CU estimates were robust to key model parameters, and were most sensitive to chemo utilization proportions. RS-guided adjuvant therapy appears to be a cost-effective strategy in both N- and N+, endocrine-sensitive breast cancer with resultant CU ratios well below commonly quoted thresholds.

Reviewing the cost-effectiveness of endocrine early breast cancer therapies: influence of differences in modeling methods on outcomes

OBJECTIVES

The purpose of this systematic review is primarily to identify published cost-effectiveness analyses and cost-utility analyses of endocrine therapies for the treatment of early breast cancer. A secondary objective is to identify whether differences in seven modeling characteristics are related to differences in outcome of these cost-effectiveness and cost-utility analyses.

METHODS

A systematic literature review was conducted to identify peer-reviewed full economic evaluations of endocrine treatments of early breast cancer published in the English language between 2000 and December 2010. Information from these publications was abstracted regarding outcome, quality, and modeling methods.

RESULTS

We identified 20 economic evaluations comprising 5 different endocrine therapeutic strategies, which are all assessed more then once. The incremental cost-effectiveness ratios (ICERs) of the reported outcomes varied widely for identical therapies. For anastrazole compared to tamoxifen, incremental life-years gained even ranged from 0.16 to 0.550 with an ICER ranging from €3,958 to €75,331. Incremental quality-adjusted life-years (QALYs) gained ranged from 0.092 to 0.378 with a cost per QALY gained varying from €3,696 to €120,265. These large differences in outcome were related to different modeling methods, with differences in time horizon and use of a carryover effect as most prominent causes.

CONCLUSION

Despite similar comparators and logical differences due to transferability issues, the outcomes of the included studies varied widely. To increase comparability and transparency of pharmacoeconomic evaluations, standardization of modeling methods for different therapeutic groups/diseases and the availability of a detailed and complete description of the model used in the evaluation is advocated. Recommendations for standardization in modeling treatment strategies in early breast cancer are presented.

Tailoring adjuvant endocrine therapy for postmenopausal breast cancer: a CYP2D6 multiple-genotype-based modeling analysis and validation

PURPOSE

Previous studies have suggested that postmenopausal women with breast cancer who present with wild-type CYP2D6 may actually have similar or superior recurrence-free survival outcomes when given tamoxifen in place of aromatase inhibitors (AIs). The present study established a CYP2D6 multiple-genotype-based model to determine the optimal endocrine therapy for patients harboring wild-type CYP2D6.

METHODS

We created a Markov model to determine whether tamoxifen or AIs maximized 5-year disease-free survival (DFS) for extensive metabolizer (EM) patients using annual hazard ratio (HR) data from the BIG 1-98 trial. We then replicated the model by evaluating 9-year event-free survival (EFS) using HR data from the ATAC trial. In addition, we employed two-way sensitivity analyses to explore the impact of HR of decreased-metabolizer (DM) and its frequency on survival by studying a range of estimates.

RESULTS

The 5-year DFS of tamoxifen-treated EM patients was 83.3%, which is similar to that of genotypically unselected patients who received an AI (83.7%). In the validation study, we further demonstrated that the 9-year EFS of tamoxifen-treated EM patients was 81.4%, which is higher than that of genotypically unselected patients receiving tamoxifen (78.4%) and similar to that of patients receiving an AI (83.2%). Two-way sensitivity analyses demonstrated the robustness of the results.

CONCLUSIONS

Our modeling analyses indicate that, among EM patients, the DFS/EFS outcome of patients receiving tamoxifen is similar to that of patients receiving an AI. Further prospective clinical trials are needed to evaluate the value of the CYP2D6 genotype in the selection of endocrine therapy.

Empirically evaluating decision-analytic models

OBJECTIVES

Model-based cost-effectiveness analyses support decision-making. To augment model credibility, evaluation via comparison to independent, empirical studies is recommended.

METHODS

We developed a structured reporting format for model evaluation and conducted a structured literature review to characterize current model evaluation recommendations and practices. As an illustration, we applied the reporting format to evaluate a microsimulation of human papillomavirus and cervical cancer. The model's outputs and uncertainty ranges were compared with multiple outcomes from a study of long-term progression from high-grade precancer (cervical intraepithelial neoplasia [CIN]) to cancer. Outcomes included 5 to 30-year cumulative cancer risk among women with and without appropriate CIN treatment. Consistency was measured by model ranges overlapping study confidence intervals.

RESULTS

The structured reporting format included: matching baseline characteristics and follow-up, reporting model and study uncertainty, and stating metrics of consistency for model and study results. Structured searches yielded 2963 articles with 67 meeting inclusion criteria and found variation in how current model evaluations are reported. Evaluation of the cervical cancer microsimulation, reported using the proposed format, showed a modeled cumulative risk of invasive cancer for inadequately treated women of 39.6% (30.9-49.7) at 30 years, compared with the study: 37.5% (28.4-48.3). For appropriately treated women, modeled risks were 1.0% (0.7-1.3) at 30 years, study: 1.5% (0.4-3.3).

CONCLUSIONS

To support external and projective validity, cost-effectiveness models should be iteratively evaluated as new studies become available, with reporting standardized to facilitate assessment. Such evaluations are particularly relevant for models used to conduct comparative effectiveness analyses.

Cost-effectiveness analysis of recurrence score-guided treatment using a 21-gene assay in early breast cancer

PURPOSE

Most guidelines for hormone receptor (HR)-positive early breast cancer recommend addition of adjuvant chemotherapy for most women, leading to overtreatment, which causes considerable morbidity and cost. There has been recent incorporation of gene expression analysis in aiding decision making. We evaluated the cost-effectiveness of recurrence score (RS)-guided treatment using 21-gene assay as compared with treatment guided by the Adjuvant! Online program (AOL).

PATIENTS AND METHODS

A Markov model was developed to compare the cost-effectiveness of treatment guided either by 21-gene assay or by AOL in a 50-year-old woman with lymph node-negative HR-positive breast cancer over a lifetime horizon. We assumed that women classified to be at high risk all received chemotherapy followed by tamoxifen and those classified to be at low risk received tamoxifen only. The model took a health care payer's perspective with results reported in 2008 Canadian dollars ($). Event rates, costs, and utilities were derived from the literature. Both costs and benefits were discounted at 5%. Outcome measures were life years gained, quality-adjusted life years (QALYs), lifetime costs, and incremental cost-effectiveness ratios (ICERs).

RESULTS

For a 50-year-old woman, RS-guided treatment was associated with an incremental lifetime cost of $4,102 and a gain in 0.065 QALY, with an ICER of $63,064 per QALY compared with AOL-guided treatment. ICER increased with increasing cost of 21-gene assay and increasing age of patients. Results were most sensitive to probabilities relating to risk categorization and recurrence rate.

CONCLUSIONS

The 21-gene assay appears cost-effective from a Canadian health care perspective.

Exemestane: a review of its use in postmenopausal women with breast cancer

Exemestane (Aromasin) is an orally active steroidal irreversible inactivator of the aromatase enzyme indicated as an adjuvant treatment in postmenopausal women with estrogen receptor-positive early-stage breast cancer following 2-3 years of adjuvant treatment with tamoxifen, and for the treatment of advanced breast cancer in postmenopausal women whose disease has progressed following tamoxifen or other antiestrogen therapy. Exemestane is effective for the treatment of postmenopausal women with early-stage or advanced breast cancer. In early-stage disease, switching to exemestane for 2-3 years after 2-3 years of adjuvant tamoxifen treatment was more effective in prolonging disease-free survival than continuing tamoxifen therapy, although it was not associated with an overall survival benefit, except in those with estrogen receptor-positive or unknown receptor status disease when nodal status, hormone replacement therapy (HRT) and chemotherapy use were adjusted for. Moreover, preliminary data suggest that the efficacy of exemestane is generally no different to that of tamoxifen in the primary adjuvant treatment of early-stage breast cancer, although exemestane may be better in prolonging the time to distant recurrence. In advanced disease, exemestane showed equivalent efficacy to megestrol in patients with disease refractory to tamoxifen and an efficacy not significantly different from that of fulvestrant in those refractory to a nonsteroidal aromatase inhibitor. Available data, some of which are limited, suggest exemestane is also effective in the first-line hormonal treatment of advanced breast cancer in postmenopausal women. Exemestane is generally well tolerated, although the potential bone fracture risk of the drug requires further investigation. Results from directly comparative trials indicating the efficacy, tolerability and bone fracture risk of exemestane relative to third-generation aromatase inhibitors and other agents in both early-stage and advanced disease, as well as the optimal sequence of endocrine therapies, are awaited with interest. In the meantime, switching to exemestane should be considered in postmenopausal women who have received 2-3 years of adjuvant tamoxifen treatment for early-stage breast cancer, and is an emerging treatment option for postmenopausal women with advanced breast cancer refractory to one or more antiestrogen therapies.

Adjuvant chemotherapy for breast cancer: a cost-utility analysis of FEC-D vs. FEC 100

BACKGROUND

Adjuvant 5-flurouracil, epirubicin and cyclophosphamide-docetaxel (FEC-D) has been shown to improve disease-free and overall survival (DFS and OS), compared to FEC 100, for node-positive breast cancer. An economic evaluation was undertaken to examine the cost-utility (CU) of FEC-D relative to FEC 100 given possible differences in cost between the two regimens.

METHODS

A Markov model was developed to calculate the cumulative costs and quality-adjusted life years (QALY) gained over a 10-year horizon for a hypothetical cohort of 1,000 women with node-positive breast cancer treated with FEC 100 or FEC-D. Event rates, costs, and utilities were derived from the literature. Efficacy outcomes were based primarily on the hazard ratio of DFS for all patients, but separate analyses were also conducted according to age and menopausal status as per the PACS 01 subgroup analysis results. The model took a third-party direct payer perspective and reports results in 2006 Canadian dollars ($). Both costs and benefits were discounted at 3%.

RESULTS

FEC-D is associated with 0.156 QALY gain and a $2,280 incremental cost compared to FEC 100, with a CU of $14,612/QALY gained. Results were robust to model assumptions and input parameters in a sensitivity analysis but were marginal in pre-menopausal and younger women.

CONCLUSIONS

Adjuvant FEC-D is a cost-effective alternative to FEC 100, with a cost-effectiveness ratio well below commonly employed thresholds. The CU according to age and menopausal status should be considered in view of the potential differences in efficacy in these subgroups, if any.

Cost-utility of adjuvant hormone therapies with aromatase inhibitors in post-menopausal women with breast cancer: upfront anastrozole, sequential tamoxifen-exemestane and extended tamoxifen-letrozole

This evaluation adapts a previous Canadian analysis of upfront and sequential adjuvant AI strategies in postmenopausal women with breast cancer to a Belgian perspective and includes an extended aromatase inhibitor (AI) strategy. A Markov model calculated monthly costs and outcomes in a hypothetical cohort of postmenopausal women with early-stage breast cancer. Baseline event rates and hazard ratios were derived from the Arimidex, Tamoxifen Alone or in Combination trial, International Exemestane Study and MA.17 trials. The analysis took a Belgian healthcare payer perspective with a 20-year time horizon. Costs and outcomes were discounted by 3%. Costs are in 2005 Euros. The cost-utility of all three strategies was favourable (<30,000 euros per QALY gained). Based on indirect comparisons using tamoxifen (TAM) alone as a common comparator, sequential TAM-AI was less costly and more effective than upfront or extended strategies. All three AI strategies were cost-effective alternatives to TAM alone, but sequential TAM-AI appears to be the economically preferred strategy.

Cost-effectiveness of switching to exemestane versus continued tamoxifen as adjuvant therapy for postmenopausal women with primary breast cancer

BACKGROUND

Sequential tamoxifen/exemestane therapy reportedly improves disease-free survival in women with primary breast cancer compared with continued tamoxifen therapy. The objective of the current study was to assess the cost-effectiveness of switching to exemestane after 2 to 3 years of tamoxifen versus continued tamoxifen in postmenopausal women with primary breast cancer for a total of 5 years of adjuvant therapy.

METHODS

A Markov model based on the Intergroup Exemestane Study (IES) population compared switching to exemestane versus continued tamoxifen for 2.5 years of therapy and 5 years of postadjuvant therapy follow-up. Disease progression and hazards ratios (HR) for recurrence and survival were determined from datasets (IES and the Surveillance, Epidemiology, and End Results program of the National Cancer Institute) and from the published literature. An expert panel validated treatment patterns, outcomes, and resource utilization. Direct medical costs were included based on published sources. Cost-effectiveness ratios were determined, and extensive sensitivity analyses were conducted.

RESULTS

Exemestane was found to be more effective than tamoxifen alone with regard to disease-free survival (2.6% absolute improvement), life-years gained (0.1028 LY), and quality-adjusted life-years gained (0.1195 QALY), at an additional cost of 2,889 Can dollars per person over 7.5 years. Incremental cost-effectiveness ratios were 28,119 Can dollars/LY gained and 24,185 Can dollars/QALY gained. The model was most sensitive to distant recurrence HR but was robust to variations in clinical, cost, and utility parameters.

CONCLUSIONS

Switching to adjuvant exemestane after 2 to 3 years of tamoxifen is cost-effective in postmenopausal women with primary breast cancer.