Letrozole or Tamoxifen for Initial Adjuvant Therapy in Breast Cancer?

The ongoing Breast International Group (BIG) 1-98 study is a large, industry-sponsored, multinational, randomized trial designed to compare breast cancer recurrence after initial adjuvant therapy with letrozole or tamoxifen. The treatment arms are:

• Letrozole for 5 years

• Tamoxifen for 5 years

• Letrozole for 2 years, followed by tamoxifen for 3 years

• Tamoxifen for 2 years, followed by letrozole for 3 years

Initial reports from this study included 2-year data on patients assigned to the monotherapy arms and data on those from the sequential-therapy arms that were censored at the time of therapy switch. The conclusions of this “primary core analysis” were that postmenopausal patients who were treated with initial letrozole, compared with tamoxifen, e…