Examining the Evidence
Aromatase inhibitors and breast cancer? Don’t write off tamoxifen
What are the findings of 3 large randomized, controlled trials on adjuvant use of aromatase inhibitors?
All 3 trials found improved disease-free survival with aromatase inhibitors in women with early-stage breast carcinoma, compared with tamoxifen.
Each aromatase inhibitor should be offered in clinical scenarios similar to those in the studies, the investigators concluded from their analysis. Each of the 3 trials focused on a single aromatase inhibitor:
- Anastrozole: 4-year disease-free survival of 86.9%, versus 84.5% in the tamoxifen group. Arimidex, Tamoxifen Alone or in Combination study
- Exemestane: 3-year disease-free survival of 91.5% for women already disease-free after 2 to 3 years of tamoxifen, versus 86.8% with 3 years of additional tamoxifen. Intergroup Exemestane Study
- Letrozole: 4-year survival of 93% for women who had completed 5 years of tamoxifen, versus 87% for no further treatment. MA-17 trial
Too little long-term data
Morandi and colleagues acknowledge the immaturity of their safety data, but give short shrift to osteoporotic fractures. With more and more women diagnosed with stage I—and even stage 0—breast tumors, I believe we must consider long-term safety data, especially in terms of osteoporotic fractures, before we make a wholesale change from selective estrogen receptor modulators (ie, tamoxifen) to aromatase inhibitors.
Match the patient to the study
While aromatase inhibitors are clearly superior in women with advanced breast cancer and probably superior in women at highest risk of recurrence, I am concerned about using them in women at extremely low risk for recurrence or mortality. We must make certain, however, that the patient we are treating has the same characteristics as the patients in the study upon which we are basing our management.
Furthermore, the American Society of Clinical Oncology Technology Assessment Working Group1,2 found that the evidence of tamoxifen’s safety and efficacy is “compelling, extensive, and long-term.” When it came to anastrozole, however, they found “extensive supporting data very promising, but insufficient to change the standard of practice at this time.”
A 5-year course of adjuvant tamoxifen remains the standard for women with hormone-receptor–positive breast cancer.
1. Winer EP, Hudis C, Burstein HJ, et al. 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. J Clin Oncol. 2002;20:3317-3327.
2. Winer EP, Hudis C, Burstein HJ, et al. American Society of Clinical Oncology technology assessment working group update: use of aromatase inhibitors in the adjuvant setting. J Clin Oncol. 2003;21:2597-2599.