Tamoxifen still has role in adjuvant breast cancer treatment
MedWire News: Sequential treatment with tamoxifen and exemestane is equivalent to exemestane alone for preventing recurrence in postmenopausal women with hormone-receptor-positive breast cancer, study results show.
The side-effect profile of the two regimes was quite different, however, and the results may therefore "play an important part in treatment decisions," say Cornelis van de Velde (Leiden University Medical Centre, The Netherlands) and colleagues in The Lancet.
For many years, tamoxifen was the standard adjuvant endocrine therapy for women with postmenopausal breast cancer, resulting in a 40% reduction in recurrence and 26% reduction in death after 5 years, note the researchers.
However, the third-generation aromatase inhibitors, including anastrozole, exemestane, and letrozol, have demonstrated better efficacy compared with tamoxifen in several adjuvant trials.
Whether the complete removal of tamoxifen from adjuvant treatment is now justified is a matter of debate.
To address this, the Tamoxifen Exemestane Adjuvant Multinational (TEAM) phase III trial was conducted in hospitals in nine countries. Postmenopausal women (median age 64 years) with hormone-receptor-positive breast cancer were randomly assigned in a 1:1 ratio to open-label exemestane (25 mg once daily; n=4904) alone or following tamoxifen (20mg once daily; n=4875) for 5 years.
After this time, 4154 (85%) patients in the sequential group and 4186 (86%) in the exemestane alone group were disease free (hazard ratio= 0.97) - a non-significant difference.
In the safety analysis, sequential treatment was associated with a higher incidence of gynecological symptoms (20% vs 11%), venous thrombosis (2% vs 1%), and endometrial abnormalities (4% vs 1%), than was exemestane alone.
Meanwhile, musculoskeletal adverse events (50% vs 44%), hypertension (6% vs 5%), and hyperlipidaemia (5% vs 3%) were reported more frequently with exemestane alone.
The researchers say these findings can be largely attributed to the respective drugs' different modes of action.
"Aromatase inhibitors reduce the concentrations of circulating oestrogen to virtually undetectable concentrations, whereas tamoxifen acts as a selective oestrogen receptor agonist that inhibits oestrogen receptors in the target breast tissue and acts as an agonist for oestrogen receptors in the heart and bone," they comment.
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By Andrew Czyzewski