American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for women with hormone receptor-positive breast cancer: status report 2002

Aromatase inhibitors for the treatment of infertility

Ovarian stimulation during infertility treatment is used either alone or in conjunction with intrauterine insemination and assisted reproductive technologies. At the present time, the two main medications used for ovarian stimulation include an oral antioestrogen, clomiphene citrate and injectable gonadotrophins. In spite of the high ovulation rate, the use of clomiphene citrate is associated with adverse side effects and low pregnancy rates. In clomiphene citrate failures, gonadotrophin injections are generally the next treatment option but, especially in polycystic ovarian syndrome, are associated with increased risk of severe ovarian hyperstimulation syndrome and high multiple pregnancies. Therefore, an effective oral treatment that could be used without risk of ovarian hyperstimulation syndrome and with minimal monitoring is preferred. It was hypothesised that aromatase inhibitors can be administered early in the follicular phase to induce ovulation by releasing the hypothalamus and/or pituitary from oestrogen negative feedback. The success of aromatase inhibitors in induction and augmentation of ovulation has been reported. In addition, increased intraovarian androgen levels may synergise with central effects of decreased oestrogen to enhance ovarian response to gonadotrophin stimulation. This increased sensitivity to follicle-stimulating hormone may be especially useful in poor responders. The potential future applications for aromatase inhibitors in infertility management are also discussed.

Future Directions in the Endocrine Therapy of Breast Cancer

Data from the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial have indicated that anastrozole ('Arimidex') may supplant tamoxifen as the preferred adjuvant endocrine therapy for hormone receptor-positive, early breast cancer in postmenopausal women. The acceptability of this change in clinical practice at this time is currently under debate, and depends upon how confident we can be that 4 years' follow-up is sufficient to allow the overall risk:benefit balance to be assessed. The data supporting the benefits of sequential endocrine therapy are more certain, and if anastrozole does become the adjuvant agent of choice, the optimal sequence of endocrine agents will need to be identified for use after recurrence on anastrozole for early disease. It will be important that new endocrine options, such as the estrogen receptor antagonist fulvestrant ('Faslodex'), are suitably incorporated into these sequences. Developments such as the sequential use of endocrine therapies in the management of breast cancer have stimulated evolving concepts in our understanding of the basic cell biology of the disease. This has emphasized the importance of understanding the interactions between the different cell-signaling pathways that underlie the development of endocrine resistance. This will present a range of new opportunities for therapeutic intervention and will provide the foundation for the rational design of clinical trials. The resulting incorporation of more target-oriented approaches and newer endocrine agents into the treatment of breast cancer should stimulate the development of promising treatment paradigms and will ultimately provide further benefit to patients.

Three Years' Follow-up from the ATAC Trial is Sufficient to Change Clinical Practice: A Debate

Tamoxifen is currently the adjuvant treatment of choice for postmenopausal women with hormone-sensitive breast cancer. However, in the treatment of postmenopausal women with advanced disease, the third-generation aromatase inhibitor anastrozole ('Arimidex') has been shown to be at least as effective as tamoxifen, and to be more effective than tamoxifen in patients with estrogen receptor-positive disease. Furthermore, anastrozole is well tolerated and is associated with fewer adverse reactions (such as thromboembolic events, vaginal bleeding, and endometrial cancer) compared with tamoxifen. A change in clinical practice has now emerged for the first-line treatment of postmenopausal advanced disease in patients, with tamoxifen becoming the second- or third-line choice for many clinicians. These data have raised questions about the optimal adjuvant treatment for postmenopausal women with early breast cancer. The 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial has compared the efficacy and safety of tamoxifen and anastrozole in the adjuvant treatment of postmenopausal women with early breast cancer. At 3 years' follow-up in the overall population, anastrozole demonstrated a significant benefit compared with tamoxifen for disease-free survival (DFS) (89.4% vs. 87.4%; p = 0.013), time to recurrence (hazard ratio = 0.79; p = 0.008), and contralateral breast cancers (odds ratio = 0.42; 95% confidence interval: 0.22-0.79; p = 0.007). Anastrozole produced improvements in quality of life similar to tamoxifen and was better tolerated for a number of predefined adverse events. Of course, a large body of evidence is available regarding the safety profile of tamoxifen and some feel that more data are needed from the ATAC trial to demonstrate that the early advantages of anastrozole over tamoxifen can be maintained in the longer term. However, a follow-up analysis at 47 months has confirmed that the tolerability profile and the absolute benefit of anastrozole were maintained over the extended follow-up period, demonstrating that the benefits of anastrozole are likely to be maintained over the long term. This review assesses these and other data from the ATAC trial and presents the arguments for and against whether 3 years' follow-up is sufficient to inform a change in clinical practice for the adjuvant treatment of postmenopausal women with early breast cancer.

Aromatase inhibitors in breast cancer: an update

BACKGROUND

Tamoxifen has been the endocrine treatment of choice for patients with breast cancer. The development of selective aromatase inhibitors has offered an alternative management approach for patients in whom a hormonal approach is indicated.

METHODS

The authors reviewed reports in which aromatase inhibitors were compared with tamoxifen for the treatment of metastatic disease, as well as information pertinent to their use as adjuvant therapy.

RESULTS

Both nonsteroidal (anastrozole and letrozole) and steroidal (exemestane) aromatase inhibitors for metastatic disease appear to provide superior efficacy and a better toxicity profile in first- and second-line treatment of metastatic disease than tamoxifen. Early results from the ATAC trial suggest anastrozole is superior to tamoxifen for disease-free survival, particularly in receptor-positive patients, and in reducing the incidence of contralateral breast cancer.

CONCLUSIONS

Aromatase inhibitors have important roles in optimal management of postmenopausal patients with hormone-responsive metastases in both the adjuvant and advanced-disease settings.

Sequencing of hormonal therapy in breast cancer

Hormonal therapy plays an integral role in the management of the majority of women with breast cancer who can be considered to have hormone-dependent breast cancer because of the presence of the molecular predictive markers, estrogen receptor and progesterone receptor. Numerous hormonal agents are available from multiple classes of drugs, including selective estrogen receptor modulators, aromatase inhibitors, progestins, androgens, and luteinizing hormone-releasing hormone analogues. Multiple clinical trials involving these agents have been conducted which permit an evidence-based approach to the development of a sequencing strategy for treatment of women with breast cancer.

American Society of Clinical Oncology technology assessment of pharmacologic interventions for breast cancer risk reduction including tamoxifen, raloxifene, and aromatase inhibition

OBJECTIVE

To update an evidence-based technology assessment of chemoprevention strategies for breast cancer risk reduction. POTENTIAL INTERVENTIONS: Tamoxifen, raloxifene, aromatase inhibition, and fenretinide.

OUTCOMES

Outcomes of interest include breast cancer incidence, breast cancer-specific survival, overall survival, and net health benefit.

EVIDENCE

A comprehensive, formal literature review was conducted for relevant topics. Testimony was collected from invited experts and interested parties. The American Society of Clinical Oncology (ASCO) prescribed technology assessment procedure was followed.

VALUES

More weight was given to published randomized trials. BENEFITS/HARMS: A woman's decision regarding breast cancer risk reduction strategies is complex and will depend on the importance and weight attributed to information regarding both cancer- and noncancer-related risks and benefits.

CONCLUSIONS

For women with a defined 5-year projected breast cancer risk of > or= 1.66%, tamoxifen (at 20 mg/d for 5 years) may be offered to reduce their risk. Risk/benefit models suggest that greatest clinical benefit with least side effects is derived from use of tamoxifen in younger (premenopausal) women (who are less likely to have thromboembolic sequelae and uterine cancer), women without a uterus, and women at higher breast cancer risk. Data do not as yet suggest that tamoxifen provides an overall health benefit or increases survival. In all circumstances, tamoxifen use should be discussed as part of an informed decision-making process with careful consideration of individually calculated risks and benefits. Use of tamoxifen combined with hormone replacement therapy or use of raloxifene, any aromatase inhibitor or inactivator, or fenretinide to lower the risk of developing breast cancer is not recommended outside of a clinical trial setting. This technology assessment represents an ongoing process and recommendations will be updated in a timely matter.

VALIDATION

The conclusions were endorsed by the ASCO Health Services Research Committee and the ASCO Board of Directors.