Abstract

BackgroundHormone receptor positive breast cancer is characterized by the potential for disease recurrence many years after initial diagnosis. Endocrine therapy has been shown to reduce the risk of such recurrence, but the optimal duration of endocrine therapy remains unclear.MethodsWe conducted a systematic review and meta-analysis to quantify the benefits and harms of extended adjuvant tamoxifen (>5 years of therapy) compared with adjuvant tamoxifen (5 years of therapy). Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for disease recurrence, death and adverse events. Subgroup analyses by timing of recurrence and baseline lymph node and menopause status were carried.ResultsFive trials comprising 21,554 patients were included. Extended adjuvant tamoxifen was not associated with a significant reduction in the risk of recurrence (OR:0.89, 95% CI 0.76–1.05, p = 0.17). There was no association between extended adjuvant tamoxifen and all-cause death (OR:0.99, 95% CI 0.84–1.16, p = 0.88). There was an apparent reduction in risk of recurrence occurring after completion of extended adjuvant tamoxifen with little evidence of effect during therapy, however, this difference was not significant (p for difference 0.10). Subgroup analysis suggested that a greater effect size among lymph node positive patients compared with those who are lymph node negative (NNT: 25 vs. 49). There was no apparent difference in the effect between pre- and post-menopausal patients. Endometrial carcinoma was substantially more frequent with extended adjuvant tamoxifen (OR:2.06, 95% CI 1.65–2.58, p<0.001, number needed to harm:89).ConclusionIn unselected patients, extended adjuvant tamoxifen is not associated with a significant reduction in recurrence, or a reduction in all-cause death. Patients with lymph node positive breast cancer may derive some benefit. Reduction in the risk of recurrence appears to occur only after completion of extended adjuvant therapy.

Highlights

  • Hormone receptor expressing breast cancers are characterized by the propensity for late recurrence with approximately 50% of recurrences and deaths occurring 10 years or more after completion of 5 years of adjuvant endocrine therapy [1]

  • The search identified a total of 2283 citations

  • Efficacy Among all randomized patients, extended adjuvant tamoxifen was not associated with a significant reduction in the odds of breast cancer recurrence

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Summary

Introduction

Hormone receptor expressing breast cancers are characterized by the propensity for late recurrence with approximately 50% of recurrences and deaths occurring 10 years or more after completion of 5 years of adjuvant endocrine therapy [1]. Methods for reducing late recurrences such as extended adjuvant hormone therapy are of interest. Both tamoxifen and aromatase inhibitors (AI) have been studied in the extended adjuvant setting. The use of AI after 5 years of adjuvant tamoxifen has shown a reduction in the risk of breast cancer recurrence in three studies [2,3,4]. Hormone receptor positive breast cancer is characterized by the potential for disease recurrence many years after initial diagnosis. Endocrine therapy has been shown to reduce the risk of such recurrence, but the optimal duration of endocrine therapy remains unclear

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