Lessons from the use of aromatase inhibitors in the neoadjuvant setting

Postmenopausal patients with oestrogen receptor-positive locally advanced T -4b, N0-1, M-0 and large operable breast cancers T-2>3 cm, T-3, T-4, N0-1 a nd M-0 have been treated with 2.5 mg letrozole (12 patients), 10 mg letrozo le (12 patients), 1 or 10 mg anastrozole (24 patients) and 20 mg tamoxifen (65 patients), There was no apparent difference in response rate between 2. 5 and 10 mg letrozole. Only 17 patients with anastrozole have so far comple ted the 3-month treatment period. Median clinical, mammographic and ultraso und reductions in tumour volumes for patients treated with letrozole were 8 1% (95% confidence interval (CI) 66-88), 77% (95% CI 64-82) and 81% (95% Cl 69-86) respectively and for anastrozole, values were 87% (95% CI 59-97), 7 3% (95% CI 58-82) and 64% (95% CI 52-76) respectively, This compares with a median reduction in tumour volume for tamoxifen-treated patients as assess ed by ultrasound of 48% (95% CI 27-48), There were seven complete clinical responses (CR), sixteen patients who achieved 50% or greater reduction in t umour volume (PR) and one no change (NC) for letrozole and four CRs, twelve PRs and one progressive disease for anastrozole. Best radiological respons es were one CR, twenty PRs and three NCs for letrozole and one CR, fifteen PRs and one NC for anastrozole. This study has shown that the new aromatase inhibitors, letrozole and anastrozole, are highly effective agents in the neoadjuvant setting and they should now be compared with tamoxifen as first -line treatment in a randomised study.