The role of aromatase inhibitors as adjuvant therapy for early breast cancer in postmenopausal women.
For endocrine therapy of hormone-sensitive advanced breast cancer in postmenopausal women, the third-generation aromatase inhibitors, letrozole, anastrozole, and exemestane, are effective both as alternatives to tamoxifen in first-line treatment and following first-line tamoxifen failure. These three agents are currently being evaluated as adjuvant therapy of early breast cancer, again relative to the standard, tamoxifen. Three treatment strategies are under investigation: replacement of tamoxifen as adjuvant therapy for 5 years (early adjuvant therapy); sequencing of tamoxifen before or after an aromatase inhibitor during the first 5 years (early sequential adjuvant therapy); or following 5 years of tamoxifen (extended adjuvant therapy). Results of the first early adjuvant trial (Arimidex, Tamoxifen Alone or in Combination [ATAC]) demonstrated that anastrozole was significantly more effective than tamoxifen in reducing the risk of disease recurrence. Two trials sequencing 2-3 years of an aromatase inhibitor after 2-3 years of tamoxifen have also reported results. A large trial (International Collaborative Cancer Group [ICCG] trial 96) found switching to exemestane to be significantly superior to continuing on tamoxifen in disease-free survival, and in a small study (Italian Tamoxifen Arimidex [ITA] trial), similarly sequencing anastrozole after tamoxifen significantly reduced the hazard of recurrence compared with remaining on tamoxifen. Extended adjuvant therapy with 5 years of letrozole versus placebo following 5 years of tamoxifen was evaluated in the MA.17 trial. Compared with placebo, letrozole resulted in a significant improvement in disease-free survival that was irrespective of whether patients had lymph node-positive or -negative tumours. Results of these four trials emphasise the important role of aromatase inhibitors in the adjuvant setting, yet the optimal approach still needs to be defined. A number of trials further evaluating the three adjuvant treatment strategies are ongoing.
Mouridsen
Henning T
HT
Department of Oncology, Rigshospitalet, 9 Blegdamsvej, Copenhagen DK-2100, Denmark. hmouridsen@rh.dk
Robert
Nicholas J
NJ
D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D017024:Chemotherapy, Adjuvant; D017326:Clinical Trials, Phase III as Topic; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D015337:Multicenter Studies as Topic; D009364:Neoplasm Recurrence, Local / Q000209:etiology; D017698:Postmenopause; D016032:Randomized Controlled Trials as Topic; D013629:Tamoxifen / Q000627:therapeutic use*; D016896:Treatment Outcome
D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D013629:Tamoxifen