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Another Role for Aromatase Inhibitors in Breast Cancer?

In a randomized trial, patients received either standard tamoxifen adjuvant therapy or sequential therapy with tamoxifen then an aromatase inhibitor.

Aromatase inhibitors -- drugs that inhibit the conversion of androgens to estrogens -- are assuming a more prominent role in breast cancer treatment. In this industry-sponsored, randomized, double-blind trial, researchers compared standard tamoxifen adjuvant therapy and sequential therapy with tamoxifen followed by exemestane, an aromatase inhibitor.

The trial included 4742 postmenopausal women who had already received 2 to 3 years of tamoxifen adjuvant therapy after surgery for nonmetastatic, mainly estrogen-receptor-positive, breast cancer. At that point, the women either continued tamoxifen for another 2 to 3 years or switched to exemestane for 2 to 3 years. After a median follow-up of 31 months, the trial was interrupted: The three-year disease-free survival rate was significantly higher in the exemestane group than in the tamoxifen group (91.5% vs. 86.8%). However, no significant difference in overall mortality was observed. Thromboembolic events and new non-breast cancers occurred significantly more often in the tamoxifen group; a nonsignificant excess of fractures occurred in the exemestane group.

Comment: These results suggest that sequential adjuvant therapy, with tamoxifen followed by exemestane, is superior to the current standard -- 5 years of tamoxifen. Unfortunately, the trial was too brief to establish a mortality benefit. In addition, it is unclear whether the difference in non-breast cancers was a chance finding and whether exemestane-induced osteoporosis will pose serious long-term problems. For now, an editorialist believes that standard tamoxifen therapy is suitable for women at low risk for recurrence, but that women at high risk are candidates for adjuvant regimens that include aromatase inhibitors.

— Allan S. Brett, MD

Published in Journal Watch General Medicine March 16, 2004

Citation(s):

Coombes RC et al. A randomized trial of exemestane after two to three years of tamoxifen therapy in postmenopausal women with primary breast cancer. N Engl J Med 2004 Mar 11; 350:1081-92.

• Medline abstract (Free)

Piccart-Gebhart MJ. New stars in the sky of treatment for early breast cancer. N Engl J Med 2004 Mar 11; 350:1140-2.

• Medline abstract (Free)

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