Long-term data confirm exemestane benefits in postmenopausal breast cancer
medwireNews: Long-term follow-up data from the TEAM trial confirm the suitability of exemestane both as a monotherapy and sequentially after tamoxifen for the treatment of postmenopausal women with hormone receptor-positive early breast cancer.
At 10 years, there were no significant differences between the monotherapy and sequential treatment groups for disease-free or overall survival, but cumulative incidence of any breast cancer recurrence was slightly lower with exemestane monotherapy, Cornelis van de Velde (Leiden University Medical Center, the Netherlands) and colleagues report in The Lancet Oncology.
The researchers explain that, after 5 years of follow-up, there was no significant difference in disease-free survival, overall survival, or relapse-free survival among the 9776 patients randomly allocated to treatment with either 5 years of oral exemestane monotherapy (25 mg once daily) or a sequential scheme of oral tamoxifen (20 mg once daily for 2.5–3.0 years) followed by exemestane for a total duration of 5 years.
At a median follow-up of 9.8 years, 921 (30%) of 3075 patients in the exemestane group and 929 (31%) of 3045 patients in the sequential group had experienced disease recurrence, defined as locoregional or distant recurrence or a new primary breast cancer. This gave a 10-year disease-free survival rate of 67% in both groups.
During follow-up, 733 (24%) patients in the exemestane group and 727 (24%) in the sequential group died, with 10-year overall survival rates at 74% and 73%, respectively.
Despite the lack of difference in disease-free and overall survival, the researchers observed a small but significant 12% decrease in the risk for breast cancer recurrence in the exemestane monotherapy group compared with the sequential group, at cumulative rates of 20% versus 22%, respectively.
The cumulative incidence of 10-year breast cancer-specific mortality rate was also lower in the exemestane monotherapy group, at 14%, than in the sequential group, at 15%, but the difference was not statistically significant in this case.
In light of this finding, van de Velde and team suggest that the “potential beneficial effect of exemestane on breast cancer-specific mortality might be counterbalanced by an increase in non-breast cancer-related mortality, leading to similar overall survival between groups.”
And indeed they found a nonsignificant increase in mortality due to causes other than breast cancer in the exemestane monotherapy group compared with the sequential group, with cumulative incidence rates of 13% versus 11%.
The authors also note that the analysis of TEAM trial data after 5 years of follow-up showed significantly more cardiovascular adverse events in the patients receiving exemestane alone than in those who received the sequential treatment, but they did not have the data to analyze long-term differences in cause of death.
Van de Velde et al conclude that their findings could enable “shared decision making between the clinician and patient, balancing individual patient characteristics and preferences, side-effect profiles, and tolerability.”
They conclude: “Future studies will hopefully show which subgroup, if any, benefits more from a particular strategy, and whether extension of any of these treatments beyond 5 years is worthwhile.”
By Laura Cowen
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