Ruth M. O'Regan, MD

Additional insight into the biology of ER-positive breast cancers, particularly the higher risk luminal B cancers, could aid in identifying potential targets and new, effective therapies. And though the majority of triple-negative breast cancers are the “basal-like” subtype, significant proportions are in other subtypes.

With the advent of aromatase
inhibitor use in the adjuvant
setting,[1] and the inception
of trials examining their use
for breast cancer prevention, it seems
prudent to evaluate what we know to
date about the long-term effects of these agents. Unfortunately, unlike selective
estrogen-receptor modulators
(SERMs)—in particular tamoxifen,[2]
which has been used for over 15 years
in patients with early-stage breast cancer-
long-term data on the use of aromatase
inhibitors are minimal.

The use of aromatase inhibitors
has increased dramatically in
the past few years as a result
of the emergence of new, more specific
agents, such as anastrozole
(Arimidex), exemestane (Aromasin),
and letrozole (Femara). This class of
agents effectively blocks the peripheral
formation of estradiol, decreasing
its concentration to less than 10%,
while maintaining selectivity.[1]
Evaluation of these selective aromatase
inhibitors as adjuvant therapy
for early-stage breast cancer was
based on the findings of trials in
metastatic breast cancer, summarized
by Visvanathan and Davidson, that
demonstrated the equivalence and,
in some cases, superiority of the
aromatase inhibitors compared
with megestrol and tamoxifen,
including their superior side-effect
profile.[2-4]