Murray J et al. – In breast cancer treatment, both letrozole and anastrozole (14-day treatment) reduce proliferation and estrogen receptor (ER) and progesterone receptor (PgR) expression Methods
Study to compare changes in proliferation following 14 days of treatment with anastrozole and letrozole
Randomization of 206 women with 209 ER-positive operable breast cancers (3 bilateral) to either 14-day treatment with 2.5 mg of letrozole or 1 mg of anastrozole prior to surgery
Analysis of changes in ER and PgR expression assessed by ALLRED scores and proliferation by Ki67
Combination of Hercept test and FISH to assess tumor HER2 status
Results
Both letrozole and anastrozole reduced ER expression (ALLRED score) by a mean of 0.32 and PgR by a mean of 2.54
Proliferation reduced by letrozole from mean of 6.37% to 0.81%; by anastrozole from 5.81% to 0.77%
Drugs showed no differences in decrease in ER, PgR, or proliferation
Both letrozole and anastrozole produced significant falls in proliferation in both HER2-positive and -negative cancers
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