EFFECT OF ANASTROZOLE ON BONE MINERAL DENSITY (ARIMIDEX)

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Effect of anastrozole (Arimidex) on bone mineral density after one year of

treatment: results from bone sub-study of the International Breast Cancer

Intervention Study (IBIS-II).

http://www.abstracts2view.com/sabcs/view.php?nu=SABCS07L_270

Singh S, Cuzick J, R, Blake G, Truscott J, J, Eastell R,

Howell A. Wolfson Institute of Preventive Medicine, London; Kings College School

of Medicine, London; University of Leeds, United Kingdom; University of

Newcastle, Australia; Christie Hospital, Manchester, United Kingdom; Northern

General

Hospital, Sheffield, United Kingdom

Background: The third generation aromatase inhibitors have been shown to

reduce bone mineral density when compared with tamoxifen in the advanced,

adjuvant

and neoadjuvant settings in women with early breast cancer. No trial to date

has compared the effect of anastrozole treatment versus placebo on bone

mineral density in the prevention setting.

Materials and Methods: The bone sub-protocol of IBIS-II assessed changes in

the bone mineral density in postmenopausal women aged 40-70 years with a high

risk of breast cancer receiving anastrozole (Arimidex ) 1 mg/day versus placebo

for 5 years. Out of 1540 women recruited to date in the prevention study, 613

women have taken part in the bone sub-protocol of the study. Lumbar spine and

femoral neck bone mineral density have been assessed at baseline and 1 year

by DEXA scans for 250 women at the time of analysis. Results are expressed as

mean percentage change. Out of 250 women, 162 with normal bone mineral

density joined stratum-I of the study and received only monitoring without

bisphosphonate treatment, 59 osteopenic women joined stratum-II and were further

randomised to receive either risedronate or placebo, 29 osteoporotic women

joined

stratum-III of the study and all received treatment with risedronate.

Results: In stratum-I, a greater bone mineral density loss was observed in

the anastrozole vs placebo group at both the lumbar spine (-2.5% vs. -0.97%; P=

..002), and total hip (-1.34 vs. -0.37%; P= .02). In stratum-II, women

randomised to risedronate (Actonel) had higher bone mineral density scores

both in

the anastrozole and in the placebo arm. The bone mineral density changes were

(risedronate vs. non-risedronate group; Spine 0.32% vs. -0.17%, P=0.75, Hip

0.67% vs. -2.27%, P= .01) in the anastrozole arm, and (Spine 0.84% vs. -0.25%,

P=.36; Hip -0.35% vs. -1.2%, P=.23) in the placebo arm. In stratum-III, the BMD

(bone mineral density) changes observed were (Spine 1.8% vs. 4.17%, P= .03;

Hip -0.13% vs. 1.5%, P=.06) in the anastrozole and placebo group, respectively.

Discussion: Women with normal bone mineral density at baseline had a

significant bone mineral density loss with anastrozole treatment. However,

women on

anastrozole, who joined the trial with an osteopenic or osteoporotic T-score,

gained bone mineral density after receiving risedronate treatment for a year.

This data confirms the bone mineral density losses observed with third

generation aromatase inhibitors on breast cancer patients, but it is also

reassuring

that bone mineral density loss can be controlled if women receive DEXA

scans at baseline and bisphosphonate treatment as needed along with aromatase

inhibitors. Longer-term follow-up and analysis on more bone mineral density

data

is required to confirm the above results. These data will be further updated

at the time of meeting.

* ASK YOUR DOCTOR FOR A BASELINE BONE DENSITY (DEXA) SCAN BEFORE STARTING

TREATMENTS (Breast Cancer Options)

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