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To switch or not to switch: should the updated Intergroup Exemestane Study alter our decision?
1University Hospital of South Manchester NHS Foundation Trust, Education & Research Centre, Southmoor Road, Wythenshawe, Manchester, M23 9LT, UK. julie.iddon@elht.nhs.uk
Expert Review of Anticancer Therapy
|December 22, 2007
Summary
Switching to exemestane after 2-3 years of tamoxifen significantly improves disease-free survival in postmenopausal women with early breast cancer. This strategy also shows a survival advantage and reduces contralateral breast cancer incidence.
Area of Science:
- Oncology
- Endocrinology
- Clinical Trials
Background:
- Aromatase inhibitors improve survival in early breast cancer compared to tamoxifen.
- Optimal timing for aromatase inhibitor use (upfront vs. sequential) in postmenopausal women with estrogen receptor-positive breast cancer remains unclear.
- Tamoxifen is a standard endocrine therapy for early breast cancer.
Purpose of the Study:
- To compare switching to exemestane versus continuing tamoxifen for adjuvant therapy in postmenopausal women with early breast cancer.
- To evaluate the impact of sequential exemestane therapy on disease-free survival and overall survival.
- To assess the effect on contralateral breast cancer incidence.
Main Methods:
- The Intergroup Exemestane Study (IES) involved 4724 postmenopausal patients with estrogen receptor-positive or unknown early breast cancer.
- Patients disease-free after 2-3 years of tamoxifen were randomized to either switch to exemestane or continue tamoxifen for a total of 5 years of endocrine therapy.
- Disease-free survival, overall survival, and contralateral breast cancer rates were analyzed.
Main Results:
- Switching to exemestane resulted in a significant disease-free survival advantage (p=0.0001) with an absolute benefit of 3.3%.
- The study demonstrated an overall survival advantage for switching to exemestane in estrogen receptor-positive breast cancer (p
- Contralateral breast cancer was reduced by 50% in both intention-to-treat and estrogen receptor-positive groups switching to exemestane.
Conclusions:
- Switching to exemestane after 2-3 years of tamoxifen is an effective strategy for the majority of early breast cancer patients, offering improved disease-free and overall survival.
- This approach reduces overall morbidity and contralateral breast cancer incidence compared to continuing tamoxifen.
- While switching appears beneficial, further results from trials like BIG 1-98 are needed to definitively resolve the optimal sequential therapy strategy.
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