The use of early adjuvant aromatase inhibitor therapy: contributions from the BIG 1-98 letrozole trial

Osteoporotic Fractures of the Spine, Hip, and Other Locations after Adjuvant Endocrine Therapy with Aromatase Inhibitors in Breast Cancer Patients: a Meta-analysis

BACKGROUND

Aromatase inhibitors (AIs) play an important role in the endocrine therapy of postmenopausal breast cancer patients, with a recent tendency to extend the duration of their use. However, AIs may increase the risk of osteoporotic bone fractures. This meta-analysis evaluated the risk of osteoporotic fractures of the hip, spine, and other locations in breast cancer patients using AIs.

METHODS

We performed a systematic search to identify randomized controlled clinical trials that investigated osteoporotic fractures in breast cancer patients on AI therapy. The main outcomes were the incidence and risk of osteoporotic fractures in general and of hip, vertebral, and non-vertebral fractures in AI users and controls.

RESULTS

The systematic review found a total of 30 randomized controlled trials including 117,974 participants. The meta-analysis showed a higher incidence of osteoporotic fracture in AI users: The crude risk ratio for all osteoporotic fractures was 1.35 (95% confidence interval [CI], 1.29-1.42; P < 0.001), for hip fractures 1.18 (95% CI, 1.02-1.35; P < 0.001), for vertebral fractures 1.84 (95% CI, 1.36-2.49; P < 0.001), and for non-vertebral fractures 1.18 (95% CI, 1.02-1.35; P < 0.001), respectively, compared to the controls.

CONCLUSION

Our meta-analysis suggested an increased risk of osteoporotic fractures for AI therapy in patients with breast cancer that was most expressed for vertebral fractures. Breast cancer patients on AIs need to be monitored for osteoporosis and osteoporotic fractures, and active prevention measures should be implemented.

A nation-wide multicenter 10-year (1999-2008) retrospective clinical study of endocrine therapy for Chinese females with breast cancer

Endocrine therapy (ET) is one of the main systemic treatments for patients with breast cancer. To our knowledge, few studies have addressed the performance of ET or relevant influencing factors in cancer treatment in China. By retrospectively analyzing the clinicopathological data on breast cancer collected from representative hospitals of 7 traditional areas in China in one random month from each year between year 1999 and 2008, we found that: 1) The rate of the use of hormone receptor (HR) testing was 83.8% (3529/4211), with the estrogen receptor-positive (ER+) rate and/or the progesterone receptor-positive (PR+) rate being 67.9% (2395/3529), and the ER-PR rate being 32.1% (1134/3529). 2) Of the 1599 patients who had received ET, 999 patients (58.3%) were premenopausal while 600 (41.7%) were postmenopausal; 1598 patients received adjuvant hormonal therapy (AHT), whereas only 1 patient received palliative therapy. The medications mainly administered to patients were anti-estrogen agents (80.3% [1283/1598]), followed by AIs (15.5% [248/1598]). Of the 1598 patients receiving AHT, 1416 patients (88.6%) were positive for ER and/or PR, while 75 (4.7%) were negative for both and 108 patients (6.7%) had unknown HR status. The ratio of the use of endocrine therapy for breast cancer patients with ER+ and/or PR+ status was 60.0% (1416/2395). 3) Results from the logistic regression analysis revealed that geography, occupations, and history of chemotherapy and surgery were dependent factors affecting the application of ET in breast cancer treatment in China (P<0.001). In conclusion, the use of ET on Chinese women with breast cancer is increasingly and gradually accounted into the standardized process. Economic status, occupations, and history of chemotherapy and surgery were key factors affecting the application of ET. People residing in developed areas, engaging in mental labour, having history of chemotherapy and surgery are susceptible to accept ET.

Approval summary: letrozole (Femara® tablets) for adjuvant and extended adjuvant postmenopausal breast cancer treatment: conversion of accelerated to full approval

On April 30, 2010, the U.S. Food and Drug Administration converted letrozole (Femara®; Novartis Pharmaceuticals Corporation, East Hanover, NJ) from accelerated to full approval for adjuvant and extended adjuvant (following 5 years of tamoxifen) treatment of postmenopausal women with hormone receptor-positive early breast cancer. The initial accelerated approvals of letrozole for adjuvant and extended adjuvant treatment on December 28, 2005 and October 29, 2004, respectively, were based on an analysis of the disease-free survival (DFS) outcome of patients followed for medians of 26 months and 28 months, respectively. Both trials were double-blind, multicenter studies. Both trials were unblinded early when an interim analysis showed a favorable letrozole effect on DFS. In updated intention-to-treat analyses of both trials, the risk for a DFS event was lower with letrozole than with tamoxifen (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.77-0.99; p = .03) in the adjuvant trial and was lower than with placebo (HR, 0.89; 95% CI, 0.76-1.03; p = .12) in the extended adjuvant trial. The latter analysis ignores the interim switch of 60% of placebo-treated patients to letrozole. Bone fractures and osteoporosis were reported more frequently following treatment with letrozole whereas tamoxifen was associated with a higher risk for endometrial proliferation and endometrial cancer. Myocardial infarction was more frequently reported with letrozole than with tamoxifen, but the incidence of thromboembolic events was higher with tamoxifen than with letrozole. Lipid-lowering medications were required for 25% of patients on letrozole and 16% of patients on tamoxifen.

Initial treatment and changes in adjuvant endocrine therapy for early stage breast cancer

Clinical trials have shown that aromatase inhibitors (AIs) are an important advance in the treatment of early stage breast cancer (ESBC), but practice patterns and the impact of treatment side effects of endocrine therapy in the community setting have not been extensively explored. This retrospective chart review describes practice patterns among patients receiving adjuvant endocrine therapy for ESBC. Charts of 200 patients with confirmed stage I-IIIA breast cancer were reviewed. Patients received first-line treatment with tamoxifen (n=96) or AIs (n=104). Fifty-one patients completed a structured interview regarding symptom burden during therapy. Time to discontinuation or switching from first-line therapy did not vary by drug class (tamoxifen vs. AI). Musculoskeletal symptoms predicted time to switching among AI patients. Tamoxifen patients who switched to AIs tended to do so following clinical guidelines for use of AIs. Interview results showed that more anastrozole than tamoxifen patients cited side effects as the reason for switching.

Estrogen receptor modulators and down regulators: optimal use in postmenopausal women with breast cancer

Endocrine treatments have been used in breast cancer since 1896, when Beatson reported on the results of oophorectomy for advanced breast cancer. In the second half of the last century, different endocrine-based compounds were developed and, in this review, the role of the selective estrogen receptor modulators (SERMs) and selective estrogen receptor down regulators (SERDs) in the postmenopausal setting are discussed. Tamoxifen is the most investigated and most widely used representative of these agents, and has been introduced in the advanced disease, in the neoadjuvant and adjuvant setting, and for the prevention of the disease. Its role has been challenged in recent years by the introduction of third-generation aromatase inhibitors that have proven higher activities than tamoxifen with different toxicity patterns. Several other SERMs have been investigated, but none have been clearly superior to tamoxifen. SERDs act as pure estrogen antagonists and should compare favourably to tamoxifen. For the time being, they have been used in the treatment of advanced breast cancers and their role in other settings still needs investigation. The increased use of aromatase inhibitors as first-line endocrine therapy has resulted in new discussions regarding the role that tamoxifen and other SERMs or SERDs may play in breast cancer. The sequencing of endocrine therapies in hormone-sensitive breast cancer remains a very important research issue.

Aromatase inhibitors: past, present and future in breast cancer therapy

Estrogen has been implicated in promoting breast cancer in a majority of women. Endocrine therapy controlling estrogen production has been the guiding principle in treating breast cancer for more than a century. A greater understanding of this disease at a molecular level has led to the development of molecules that inhibit estrogen production by inhibiting the aromatase enzyme, that is the primary source of estrogen in postmenopausal women. This review examines the evolution of aromatase inhibitor (AI) based therapies over the past three decades. The third generation aromatase inhibitors (anastrozole, letrozole and exemestane), which have been found to be extremely specific and effective in an adjuvant/neoadjuvant/extended adjuvant setting are discussed from a biochemical and clinical perspective. A comprehensive discussion of the past, present, and future of aromatase inhibitors is conducted in this review.