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Letrozole Monotherapy Shows Breast CA Long-Term Benefits

Sequential treatments with letrozole and tamoxifen have similar outcomes to letrozole monotherapy

FRIDAY, Oct. 21 (HealthDay News) -- For postmenopausal women with hormone receptor-positive early breast cancer, letrozole monotherapy reduces breast cancer recurrence and mortality in the long-term more effectively than tamoxifen monotherapy, according to a study published online Oct. 21 in The Lancet Oncology.

Meredith M. Regan, Sc.D., from the Dana-Farber Cancer Institute in Boston, and colleagues presented an update of efficacy outcomes in the Breast International Group (BIG) 1-98 study at a median follow-up of 8.1 years. The study was undertaken to investigate the efficacy of letrozole and tamoxifen monotherapy and sequential therapy in 8,010 postmenopausal women with hormone receptor-positive breast cancer. For sequential therapy, participants were randomly assigned to four arms: five-year monotherapy with either tamoxifen or letrozole, or sequential treatment with two years of letrozole followed by three years tamoxifen, or vice versa. Disease-free survival, overall survival, distant recurrence-free interval (DRFI), and breast cancer-free interval (BCFI) were the study end points. Treatment has ended for all groups, and follow-up is ongoing.

The investigators found that letrozole monotherapy was significantly better than tamoxifen by inverse probability of censoring weighting or intention-to-treat analysis for DFS (hazard ratio [HR], 0.82 and 0.86, respectively), overall survival (HR, 0.79 and 0.87, respectively), DRFI (HR, 0.79 and 0.86, respectively), and BCFI (HR, 0.80 and 0.86, respectively). There were no significant differences in the median eight year follow-up results of the four end points on comparing the sequential groups with letrozole monotherapy.

"This update of BIG 1-98 at 8.1 years median follow-up reinforces the evidence that letrozole monotherapy is better than tamoxifen," the authors write.

Several authors disclosed financial relationships with pharmaceutical companies, including Novartis, which funded the study and manufactures letrozole.

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