Maintenance hormone therapy with letrozole after first-line chemotherapy for advanced breast cancer

Maintenance hormone therapy after first-line chemotherapy is routinely used by many clinicians in advanced breast cancer patients with potentially hormone-sensitive tumors, although there are insufficient evidences in the literature to support this practice. We investigated the effects of the third-generation aromatase inhibitor letrozole as a maintenance therapy in postmenopausal patients who had responded or had stable disease with first-line chemotherapy.

Fifty-eight patients (median age 62 years, range 31-80) were recruited and received letrozole, 2.5 mg/day starting within 8 weeks since the last cycle of chemotherapy. Estrogen and/or progesterone receptor status was positive in 81% of the patients, unknown in 19%; 57% of the patients had visceral disease. First-line chemotherapy included anthracyclines and/or taxanes in 74% of cases.

The median time to progression (TTP) from starting letrozole was 18.5 months. A shorter TTP was found in patients with abnormal CA 15-3 levels at the start of maintenance letrozole (median TTP, 9.9 months: p = 0.01), or with levels increasing >25% from baseline during the first 6 months of letrozole therapy (median TTP, 8.2 months: p < 0.0001). Response status improved during letrozole in 15.5% of patients who had obtained less than a complete response to chemotherapy. Maintenance treatment was well tolerated and had no significant impact on quality of life scores.

This study provides evidence in support of the common clinical practice of maintenance hormone therapy after chemotherapy in suitably selected patients with advanced breast cancer.