American Society of Clinical Oncology 2003 update on the role of bisphosphonates and bone health issues in women with breast cancer

Metastatic breast carcinoma confined to bone: portrait of a clinical entity

BACKGROUND

The current study was performed to study metastatic breast carcinoma that remains confined to bone.

METHODS

The medical notes of 2514 breast carcinoma patients who were treated in 2 academic units over a 20-year period were screened and patients who fulfilled the following criteria were selected: 1) clinical manifestation and imaging confirmation of bone metastases, and 2) metastatic disease remaining confined to bone for a minimum of 24 months. Available clinical and pathologic data were recorded and analyzed. The objective of the current study was to describe this clinical entity and investigate possible correlations between clinicopathologic parameters and clinical outcome.

RESULTS

A total of 104 patients (4% of the total screened patient population) fulfilled the study criteria. The majority of patients were postmenopausal, with a median age of 58 years; 44 of the patients were found to have metastases at the time of presentation (M1) and 60 patients developed metastases at a median of 38 months (range, 8-160 months) after surgery for the primary tumor. Metastases remained confined to bone for a median of 50 months. Survival after the diagnosis of bony metastases was 72 months and was similar in the 2 groups (66 months vs. 78 months). Of the patients treated, 80% responded to hormonal therapy, and 76.5% responded to chemotherapy. There was no association noted between survival and tumor grade, anatomic distribution, or disease extension.

CONCLUSIONS

Bone-confined metastatic breast carcinoma has an indolent clinical course that alleviates the need for vigorous follow-up and calls into question aggressive therapeutic approaches in these patients. Translational studies are warranted to map the molecular profile, leading to the development of targeted therapies in this group of patients.

Bisphosphonates in the treatment of skeletal metastases

Metastatic bone disease puts an enormous burden on patients and health care resources. Disruption of normal bone homeostasis by bone metastases leads to troublesome skeletal complications, such as bone pain, pathologic fractures, hypercalcemia of malignancy, and spinal cord compression. Bisphosphonates are an effective treatment for skeletal complications. These agents act primarily by initiating biochemical processes that ultimately result in apoptosis of osteoclasts, but they also have a number of other antitumor functions (eg, inhibition of angiogenesis). At present, the most widely used bisphosphonates are oral clodronate and intravenous pamidronate and zoledronic acid. Although these agents are effective in reducing skeletal complications, they are associated with varying safety and convenience issues. More recently, the availability of ibandronate as intravenous and oral formulations represents a new alternative for the treatment of metastatic bone disease. Further studies are necessary to establish the comparative benefits of bisphosphonates in metastatic bone disease.

A Method for Making Estimates of the Benefit of the Late Use of Letrozole in Patients Completing 5 Years of Tamoxifen

This article discusses the rationale for 2 methods of making estimates of the benefit of letrozole as extended adjuvant hormonal therapy after 5 years of tamoxifen. It uses information from the Overview metaanalyses to develop general rules for making estimates of remaining risk of relapse for women completing 5 years of adjuvant tamoxifen without relapse. The first derived method shows that the expected benefit for such a woman is approximately one tenth of her risk of relapse in years 0-10 if untreated. The second method uses a modification of Adjuvant!, a decision support tool, and makes similar estimates. The decision tool supplies needed estimates of initial risk and allows adjustment for competing mortality. Uncertainties involved in making these estimates are also discussed.

Profiling the safety and tolerability of bisphosphonates

Because patients with metastatic bone disease suffer a significant burden from their illness and from anticancer treatments, it is therefore important to minimize the side effects of bisphosphonates. The intravenous bisphosphonates, zoledronic acid and pamidronate, have tolerability issues that include a flu-like syndrome, injection-site reactions, and occasional renal toxicity. Because of the potentially severe nature of the renal toxicity, renal monitoring is required before each dose, with drug withdrawal if the patients' renal function deteriorates. Oral clodronate often causes gastrointestinal disturbances, particularly diarrhea; compliance is often poor because of the large tablet size and multiple daily dosing. Long-term data have shown that the bisphosphonate ibandronate is well tolerated either intravenously or orally, with a renal safety profile similar to placebo and no evidence of cumulative renal damage. Studies investigating the effects of 15-minute infusions and intensive dosing indicate that intravenous ibandronate given rapidly or at high doses is also well tolerated with no renal safety concerns. Taken together, these results suggest that the favorable safety profile of ibandronate provides an important alternative to existing bisphosphonate options for metastatic bone disease. Using ibandronate could improve patient acceptability and simplify management, with reductions in the need for safety monitoring and management of adverse events.

Patient management issues in metastatic bone disease

The main goals of bisphosphonate therapy are to prevent and treat skeletal events, minimize disability, and relieve pain without increasing the overall burden that bone metastases (and their treatment) place on patients. The ease and convenience of treatment are important to patients, and there are data suggesting that patients prefer oral therapy over intravenous drugs to help them maintain a normal life. Intravenous therapy with zoledronic acid and pamidronate is currently time-consuming; preparation, renal monitoring, infusion, and follow-up use valuable health care resources. Intravenous ibandronate could help alleviate this burden because of its good renal safety profile. Although efficacious, oral clodronate has compliance problems because of multiple dosing, large tablet size, and gastrointestinal tolerability issues. Recent phase III trials of oral ibandronate have shown efficacy similar to that of intravenous ibandronate, with no compliance or tolerability concerns. Ibandronate appears to have several advantages over current therapies that could improve treatment acceptability and reduce the burden of disease on the health care system. Research continues into the efficacy, safety, and pharmacoeconomics of ibandronate.

Medical management of skeletal metastasis

This article discusses general principles of medical management of bone metastases, including diagnosis and follow-up; management of specific symptoms; options for systemic treatment, including bisphosphonates; specific details about each cancer type; and future directions in therapy.

Assessment of therapeutic response in patients with metastatic bone disease

Metastatic bone disease is common in cancer patients and causes substantial disease-related morbidity and mortality. However, several effective treatments are available for the management of these patients. Bisphosphonates, which inhibit osteoclast-mediated resorption of bone matrix, are especially important because they decrease the incidence of skeletal-related events in many tumour types and can complement antineoplastic therapies. At present, assessment of treatment for bone metastases is hindered by a lack of effective, rapid methods to measure disease response. We discuss the difficulties of current measures of response assessment and describe the development of new radiological and biochemical markers of bone metastases. Assays that detect type I collagen telopeptides as markers of bone resorption seem to be most promising at present.

Optimizing bisphosphonate therapy in patients with breast cancer on endocrine therapy

Deterioration of bone health is a major concern during progression and treatment of patients with breast cancer, especially in postmenopausal women. Disease- and treatment-associated skeletal-related events include fractures, spinal compression, bone pain, and hypercalcemia of malignancy. Bisphosphonates, which inhibit osteoclastic bone resorption, are important new agents in the management of skeletal-related events, and their impact on breast cancer-related bone metastases and on bone loss during long-term estrogen deprivation therapies such as aromatase inhibitors is reviewed. Intravenous pamidronate has become the standard bisphosphonate to reduce or delay skeletal complications of advanced breast cancer bone metastases, but the more potent agent, zoledronic acid, appears to be at least as effective. Another agent, ibandronate, is also active but has not been investigated in comparison with the other intravenous bisphosphonates. Zoledronic acid is the most convenient to administer, requiring only a short infusion. The effects of bisphosphonates on bone health in women with early breast cancer are also being investigated. A single yearly infusion of zoledronic acid has been shown to significantly increase bone mineral density in osteoporotic postmenopausal women and to reduce biochemical markers of bone turnover. The possibility of such treatment-reversing aromatase inhibitor-associated bone loss during adjuvant therapy of breast cancer is being evaluated in a trial of letrozole, with zoledronic acid added initially or after the onset of bone loss or fracture.

Ibandronate reduces skeletal morbidity in patients with breast cancer

Three phase III studies have assessed the efficacy of intravenous (IV) and oral ibandronate over 96 weeks for metastatic bone disease in patients with breast cancer. The primary endpoint for each trial was the skeletal morbidity period rate, defined as the number of 12-week periods with new bone complications, adjusted for the time spent on study. Both IV ibandronate 6 mg every 3 to 4 weeks and oral ibandronate 50 mg once daily significantly reduced the skeletal morbidity period rate compared with placebo ( P = .004 in each case). The studies were not powered to detect statistical significance on individual components of the skeletal morbidity period rate. Nevertheless, IV ibandronate significantly reduced vertebral fractures and the need for radiotherapy, while oral ibandronate led to significantly fewer bone events needing radiotherapy or surgery than placebo. Using a multivariate Poisson regression model, the mean reduction in the relative risk of new bone events compared with placebo was 40% with IV ibandronate 6 mg ( P = .0033), and 38% with oral ibandronate 50 mg ( P <.001). The clinical equivalence of IV and oral ibandronate was confirmed by a post-hoc Anderson-Gill analysis of time to multiple skeletal events. These results show that IV and oral ibandronate effectively reduce skeletal morbidity in breast cancer patients with bone metastases.

Skeletal Complications in Patients with Bone Metastases from Renal Cell Carcinoma and Therapeutic Benefits of Zoledronic Acid

Bone metastases in patients with renal cell carcinoma are associated with a high risk of skeletal complications. Therefore, a subset analysis of a larger clinical trial was performed to determine the efficacy of zoledronic acid in renal cell carcinoma patients. Patients with bone metastases from solid tumors other than breast or prostate cancer (n=773) were randomized to receive zoledronic acid or placebo via 15-minute infusion every 3 weeks for 9 months. Patients were monitored for skeletal-related events, which were defined as pathological fracture, spinal cord compression, radiotherapy, or surgery to bone. Among the subset of 74 patients with renal cell carcinoma, 46 patients were treated with 4 mg of zoledronic acid or placebo. Significantly fewer patients treated with 4 mg zoledronic acid had a skeletal-related event (37% versus 74% for placebo, P=0.015), and zoledronic acid significantly prolonged the time to first skeletal-related event (median not reached at 9 months versus 72 days for placebo; P=0.006). Zoledronic acid significantly reduced the annual incidence of skeletal-related events by approximately 21% (mean 2.68 versus 3.38 events per year for placebo, P=0.014) and significantly reduced the risk of developing a skeletal-related event by 61% compared with placebo (risk ratio=0.394, P=0.008) by multiple event analysis. Median time to progression of bone lesions was also significantly extended with zoledronic acid treatment (P=0.014). Zoledronic acid is the first bisphosphonate to significantly reduce skeletal morbidity and significantly prolong time to bone lesion progression in patients with bone metastases from renal cell carcinoma.

Toward New Horizons: The Future of Bisphosphonate Therapy

Bisphosphonate therapy has become a standard of care for patients with malignant bone disease. In addition, preclinical and preliminary clinical data suggest that bisphosphonates may prevent cancer-treatment-induced bone loss (CTIBL) and the development of malignant bone disease in patients with early-stage cancer. Patients who receive adjuvant hormonal therapy for breast cancer or androgen-deprivation therapy for prostate cancer are at an especially high risk for CTIBL because of reduced estrogenic signaling. Oral clodronate (Bonefos; Anthra Pharmaceuticals; Princeton, NJ), oral risedronate (Actonel; Proctor and Gamble Pharmaceuticals, Inc.; Cincinnati, OH), and i.v. zoledronic acid (Zometa; Novartis Pharmaceuticals Corp.; East Hanover, NJ) have all demonstrated promise in preventing CTIBL in patients receiving hormonal therapy for breast cancer. Zoledronic acid has demonstrated efficacy with the longest between-treatment interval (3-6 months) and is currently being investigated in the Zometa/Femara Adjuvant Synergy Trials (Z-FAST and ZO-FAST in the United States and Europe, respectively). In patients receiving androgen-deprivation therapy for prostate cancer, i.v. pamidronate (Aredia; Novartis Pharmaceuticals Corp.) and i.v. zoledronic acid both have demonstrated significant benefits over placebo, but only zoledronic acid produced significant increases in bone mineral density compared with baseline values. Additionally, bisphosphonates have demonstrated antitumor activities in preclinical models, and clinical trials with oral clodronate suggest that bisphosphonates might prevent or delay bone metastasis in patients with early-stage breast cancer. Clinical trials are investigating the effect of zoledronic acid on disease progression in patients with breast cancer, prostate cancer, and non-small cell lung cancer. The results of these clinical trials should further define the clinical benefit of bisphosphonates in the oncology setting.

Safety of Intravenous and Oral Bisphosphonates and Compliance With Dosing Regimens

Patients with advanced cancers--particularly breast and prostate cancers--are at high risk for bone metastasis, leading to accelerated bone resorption and clinically significant skeletal morbidity. Bisphosphonates are effective inhibitors of bone resorption and reduce the risk of skeletal complications in patients with bone metastases. The standard routes of administration for bisphosphonates used in clinical practice are either oral or i.v. infusion. Oral administration of bisphosphonates is complicated by poor bioavailability (generally <5%) and poor gastrointestinal tolerability. First-generation bisphosphonates, such as clodronate (Bonefos; Anthra Pharmaceuticals; Princeton, NJ), must be administered at high oral doses (1,600-3,200 mg/day) to achieve therapeutic effects, which leads to poor tolerability and compliance with oral dosing regimens. Infusion of bisphosphonates is associated with dose- and infusion-rate-dependent effects on renal function. In particular, high bisphosphonate doses (e.g., 1,500 mg clodronate) can cause severe renal toxicity unless infused slowly over many hours. In contrast, the newer, more potent bisphosphonates effectively inhibit bone resorption at micromolar concentrations, and the small doses required can be administered via relatively short i.v. infusions without adversely affecting renal function. Zoledronic acid (Zometa; Novartis Pharmaceuticals Corp.; East Hanover, NJ) is a new generation bisphosphonate, and the recommended dose of 4 mg can be safely infused over 15 minutes. The 90-mg dose of pamidronate (Aredia; Novartis Pharmaceuticals Corp.) and the 6-mg dose of ibandronate (Bondronat; Hoffmann-La Roche Inc.; Nutley, NJ) require 1- to 4-hour infusions. Intravenous bisphosphonates require less frequent dosing (once a month) and are generally well tolerated with long-term use in patients with bone metastases. Zoledronic acid has demonstrated the broadest clinical activity in patients with bone metastases.

Bisphosphonate use for the management of breast cancer patients with bone metastases: a survey of Canadian Medical Oncologists

BACKGROUND

The use of bisphosphonates (BP) in breast cancer patients with bone metastases (BM) has been shown to reduce bone pain and lower the risk of skeletal-related events (SREs). Many practice guidelines exist for the use of BPs in patients with BM. Unfortunately, none clearly address whether the benefits of BP use apply equally to all subgroups of patients, the duration of therapy, and when to discontinue BP therapy. A questionnaire was therefore developed and administered to determine how medical oncologists in Canada use BPs in clinical practice.

METHODS

A structured mailing strategy was adopted. The population consisted of 100 medical oncologists with active breast cancer practices in Canada. All regions of Canada were represented. The questionnaire was developed to capture data on respondent demographics, BPs used, major factors influencing decision making, and clinical practice in situations where there is a lack of high-quality data.

RESULTS

Completed questionnaires were returned by 76 medical oncologists. All treated breast cancer and the majority (68%) were based at teaching hospitals. Ninety-six percent of respondents regularly prescribed BPs, initiating therapy at the time the patient presented with BM. Although 79% of respondents recognized that there was no clear data to support the continued use of BP after bony progression, 53% stated that they rarely or never discontinue a BP once started. In situations where a BP was discontinued, the majority of respondents report the reason for discontinuation was a decrease in patient performance status. In the patient with clearly progressive visceral metastases and an estimated prognosis of less than 6 months, 75% of respondents would still commence BP therapy.

CONCLUSIONS

This study confirms that most medical oncologists in Canada, while acknowledging lack of evidence, maintain patients on BP therapy when patients have an expected survival of less than 6 months or even after patients progress while on a BP. More research is needed to determine the role of continuing, switching, or discontinuing BP therapy in the context of disease progression or shortened expected survival.

Understanding treatments for bone loss and bone metastases in patients with prostate cancer: a practical review and guide for the clinician

Prostate cancer patients are at risk for developing bone loss and bone metastases. Clinicians prescribing ADT should appreciate the potential effects of ADT on BMD as well as the morbidity and mortality that can result from osteoporotic fractures. Measures to address the evaluation of patients and when to treat patients with significant bone loss have been discussed. Bisphosphonates effectively prevent loss of BMD in prostate cancer patients. Treatment of prostate cancer patients with established bone metastases with zoledronic acid should be considered strongly based on the results of the Saad study and other studies of patients with bone metastases with other malignancies. Zoledronic acid is approved by the US FDA for use in men with metastatic hormone-refractory prostate cancer and in the European Union for any patient with bone metastases, including prostate cancer patients,because of the beneficial impact of zoledronic acid on skeletal-related events. There is no validated method to determine which patients might benefit most from bisphosphonate therapy in this setting. Many questions about the use of bisphosphonate therapy in men with prostate cancer must be addressed, both in terms of the use in bone loss and bone metastases. These questions include: What is the optimal timing of therapy? Which bisphosphonate is best? What is the best dose and dose schedule? Do bisphosphonates effectively decrease skeletal fracture rates in patients with osteoporosis? How long should patients receive therapy? Are bisphosphonate "holidays" warranted? What are the long-term skeletal and renal toxicities? Is there a role for sequencing bisphosphonate therapy either before or after chemotherapy? Is bisphosphonate therapy synergistic with certain chemotherapy or other bone-targeted therapies? Which patients are the most likely to benefit from bisphosphonate therapy? What are clinically significant endpoints of bisphosphonate trials in patients with metastatic disease? Does inhibiting bone turnover also inhibit formation of bone metastases? Preliminary work in these areas has been completed, but more questions than answers are available. Given the rising costs of health care, it is imperative that these questions be addressed to best use the health care dollar while offering high-risk patients the best available therapy. At present, no data suggest that bisphosphonates should be used routinely to prevent BMD loss in men with normal BMD or to prevent the development of bone metastases in men with biochemical relapse. Continuing trials may give us guidance in the future.

Long-Term Efficacy of Zoledronic Acid for the Prevention of Skeletal Complications in Patients With Metastatic Hormone-Refractory Prostate Cancer

In a placebo-controlled randomized clinical trial, zoledronic acid (4 mg via a 15-minute infusion every 3 weeks for 15 months) reduced the incidence of skeletal-related events (SREs) in men with hormone-refractory metastatic prostate cancer. Among 122 patients who completed a total of 24 months on study, fewer patients in the 4-mg zoledronic acid group than in the placebo group had at least one SRE (38% versus 49%, difference = -11.0%, 95% confidence interval [CI] = -20.2% to -1.3%; P =.028), and the annual incidence of SREs was 0.77 for the 4-mg zoledronic acid group versus 1.47 for the placebo group (P=.005). The median time to the first SRE was 488 days for the 4-mg zoledronic acid group versus 321 days for the placebo group (P =.009). Compared with placebo, 4 mg of zoledronic acid reduced the ongoing risk of SREs by 36% (risk ratio = 0.64, 95% CI = 0.485 to 0.845; P =.002). Patients in the 4-mg zoledronic acid group had a lower incidence of SREs than did patients in the placebo group, regardless of whether they had an SRE prior to entry in the study. Long-term treatment with 4 mg of zoledronic acid is safe and provides sustained clinical benefits for men with metastatic hormone-refractory prostate cancer.

The curability of breast cancer and the treatment of advanced disease

Breast cancer represents a major health problem, with more than 1,000,000 new cases and 370,000 deaths yearly worldwide. In the last decade, in spite of an increasing incidence, breast cancer mortality has been declining in the majority of developed countries. This is the combined result of better education, widespread screening programmes and more efficacious adjuvant treatments. Better knowledge of breast cancer biology now allows the cosmetic, physical and psychological consequences of radical mastectomy to be spared in the majority of breast cancer patients. Use of the sentinel node technique is rapidly expanding and this will further reduce the extent and the consequences of surgery. Several clinico-pathological factors are used to discriminate between patients at low (<10%), average (10-40%) and high risk of relapse. Nodal status, tumour size, tumour grade and age are accepted universally as important factors to define risk categories. Newer factors such as uPA/PAI-1, HERer2-neu, proliferative indices and gene expression profile are promising and will allow better discrimination between patients at different risk. Endocrine manipulation with tamoxifen, ovarian ablation or both is the preferred option in the case of endocrine-responsive tumours. Tamoxifen administered for 5 years is the standard treatment for postmenopausal patients; tamoxifen plus ovarian ablation is more effective than tamoxifen alone for premenopausal women. Recent data demonstrate that, for postmenopausal patients, the aromatase inhibitors are superior to tamoxifen, with a different safety profile. At present, anastrozole can be used in the adjuvant setting in cases of tamoxifen intolerance or toxicity. Chemotherapy is the treatment of choice for steroid receptor-negative tumours. Polychemotherapy is superior to single agents and anthracycline-containing regimens are superior to CMF. Six courses of FEC or FAC or the sequential administration of four doses of anthracycline followed by four of CMF are the recommended regimens. New regimens including the taxanes have produced a further improvement in risk reduction and are reasonable therapeutic options. The taxanes have been approved for adjuvant therapy in the USA, while European approval is pending. Combined endocrine-chemotherapy is the standard adjuvant treatment in high-risk patients with endocrine-responsive tumours. Endocrine manipulation is usually administered after completion of the chemotherapy programme. For HER2-neu overexpressing tumours, several rapidly accruing trials are exploring the potential additive effect of trastuzumab, a monoclonal antibody directed against the extramembrane portion of the HER2 receptor. Primary chemotherapy is increasingly used in the treatment of locally advanced and operable breast cancer, with increased rates of breast-conserving surgery. A proportion of patients achieve a pathological complete response and these patients have significantly better long-term outcomes. Twenty-five to forty percent of breast cancer patients develop distant metastases. At this stage the disease is incurable; however, treatments can assure a significant prolongation of survival, symptomatic control and maintenance of quality of life. In the case of hormone receptor positivity and in the absence of visceral, life-threatening disease, endocrine manipulation is the treatment of choice. Active treatments include tamoxifen, ovarian ablation, aromatase inhibitors, pure anti-oestrogens and progestins. Aromatase inhibitors are the most active agents, but the choice and the sequence of endocrine therapies are also dictated by prior adjuvant treatment. Chemotherapy has to be preferred in cases of receptor-negative tumours, acquired resistance to hormones and aggressive visceral disease. Combination regimens are usually associated with higher response rates and sometimes survival prolongation, and this approach should be recommended in young patients with good performance status and visceral disease. On the other hand, single agents have a better tolerability profile and should be tand should be the treatment of choice when a careful balance between activity and tolerability is needed. For HER2-neu positive tumours, the combination of trastuzumab and chemotherapy is significantly superior to chemotherapy alone in terms of both response rates and survival. Other useful palliative treatments include bisphosphonates for the control of metastatic bone disease and radiotherapy for painful bone lesions or local relapses.

Calcium and vitamin D supplementation during bisphosphonate administration may increase osteoclastic activity in patients with bone metastasis

Bone metastasis are a frequent complication of cancer, occurring in up to 70% of patients with advanced breast or prostate cancer. The consequences of bone metastasis are often devastating. Osteolytic metastasis can cause different kinds of skeletal related events including severe pain, pathologic fractures, life-threatening hypercalcemia, spinal cord compression, and other nerve-compression syndromes. These skeletal-related events are the result of the resorption of mineralized bone by osteoclasts. Bisphosphonates are synthetic analogues of naturally occurring pyrophosphate compounds that inhibit bone resorption. Potent bisphosphonates, pamidronate and, more importantly zoledronic acid may cause hypocalcemia, but mostly asymptomatic, mild, transient in most cases. Sufficient calcium and vitamin D intake needs to be ensured in patients with malignancy who have borderline or low levels of calcium when commencing treatment with bisphosphonates. Vitamin D itself induce the formation of osteoclasts by increasing the expression of RANKL on marrow stromal cells. Local calcium also promotes tumor growth and the production of parathyroid hormone-related peptide which in turn stimulates bone resorption. Vitamin D and calcium supplementation during bisphosphonate administration for the purpose of elimination of the side effects related to hypocalcemia in patients with bone metastasis may increase the bone resorption and decrease the efficacy of bisphosphonates. Therefore, vitamin D and calcium supplementation must not be routinely recommended during bisphosphonate administration.

Benefit and projected cost-effectiveness of anastrozole versus tamoxifen as initial adjuvant therapy for patients with early-stage estrogen receptor-positive breast cancer

BACKGROUND

Women who have estrogen receptor (ER)-positive disease with postmenopausal onset and who receive tamoxifen as standard adjuvant treatment constitute the largest subgroup of patients with breast cancer. Recent data from the ATAC ('Arimidex, Tamoxifen Alone or in Combination') randomized trial indicate that anastrozole significantly reduces breast cancer recurrence rates but does not provide any advantage in terms of survival at 4 years posttreatment. Furthermore, anastrozole and tamoxifen were found to have different toxicity profiles. The goals of the current study were to estimate the disease-free survival (DFS) rates and potential survival benefits associated with anastrozole use and to determine whether the incremental cost-effectiveness (ICE) was low enough to warrant an immediate switch to the use of this agent, as the long-term conclusions of the ATAC trial will not be available for several years.

METHODS

A computer simulation model assessed the outcomes of 64-year-old women with ER-positive breast cancer who subsequently received either anastrozole or tamoxifen for 5 years. Daily recurrence risks, as well as the relative risks associated with various treatment-related events, were calculated using data from the ATAC trial. Study endpoints included breast cancer recurrence-free survival, anticipated survival resulting from an anastrozole-induced decrease in systemic disease recurrence rates, and survival adjusted for quality of life and for hip fracture risk over periods of 4, 12, and 20 years.

RESULTS

After 4 years, the projected DFS benefit associated with anastrozole was 14 days, with an ICE of $167,500 per year. Projected 12 and 20 years into the future, DFS benefits increased to 2.9 months and 5.3 months, respectively. The corresponding benefits in terms of overall survival were 0.9 months and 2.0 months, respectively, with the ICE becoming < $100,000 per life year once the projection horizon exceeded 12 years. The inclusion of quality-of-life weightings for nonfatal outcomes modestly favored anastrozole in the short term; however, if anastrozole use is associated with an increased risk of hip fracture, then the long-term benefit associated with this agent is reduced by approximately 25%.

CONCLUSIONS

Adjuvant anastrozole is projected to result in a substantial improvement in DFS for patients with breast cancer. If this DFS benefit were to ultimately lead to a survival benefit, then the ICE of anastrozole use would be acceptable for patients expected to live longer than 12 years. Decision models are useful for generating realistic projections for stakeholders who are considering competing options that impact survival and quality of life and have associated societal costs.