Switching of postmenopausal women with endocrine-responsive early breast cancer to anastrozole after 2 years' adjuvant tamoxifen: combined results of ABCSG trial 8 and ARNO 95 trial.
BACKGROUND
Tamoxifen has been the standard adjuvant treatment for postmenopausal women with hormone-responsive early breast cancer for more than 20 years. However, the third-generation aromatase inhibitor anastrozole has proven efficacy and tolerability benefits compared with tamoxifen when used as initial adjuvant therapy. We investigate whether women who have received a period of adjuvant tamoxifen would benefit from being switched to anastrozole.


METHODS
We present a combined analysis of data from two prospective, multicentre, randomised, open-label trials with nearly identical inclusion criteria. Postmenopausal women with hormone-sensitive early breast cancer who had completed 2 years' adjuvant oral tamoxifen (20 or 30 mg daily) were randomised to receive 1 mg oral anastrozole (n=1618) or 20 or 30 mg tamoxifen (n=1606) daily for the remainder of their adjuvant therapy. The primary endpoint was event-free survival, with an event defined as local or distant metastasis, or contralateral breast cancer. Analysis was by intention to treat.


RESULTS
3224 patients were included in analyses. At a median follow-up of 28 months, we noted a 40% decrease in the risk for an event in the anastrozole group as compared with the tamoxifen group (67 events with anastrozole vs 110 with tamoxifen, hazard ratio 0.60, 95% CI 0.44-0.81, p=0.0009). Both study treatments were well tolerated. There were significantly more fractures (p=0.015) and significantly fewer thromboses (p=0.034) in patients treated with anastrozole than in those on tamoxifen.


CONCLUSIONS
These data lend support to a switch from tamoxifen to anastrozole in patients who have completed 2 years' adjuvant tamoxifen.
Jakesz
Raimund
R
Austrian Breast and Colorectal Cancer Study Group (ABCSG), Vienna Medical University, Vienna General Hospital, Waehringer Guertel 18-20, Vienna A-1090, Austria. raimund.jakesz@meduniwien.ac.at
Jonat
Walter
W
Gnant
Michael
M
Mittlboeck
Martina
M
Greil
Richard
R
Tausch
Christoph
C
Hilfrich
Joern
J
Kwasny
Werner
W
Menzel
Christian
C
Samonigg
Hellmut
H
Seifert
Michael
M
Gademann
Guenther
G
Kaufmann
Manfred
M
Wolfgang
Johann
J
D000368:Aged; D000077384:Anastrozole; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D009570:Nitriles / Q000009:adverse effects / Q000627:therapeutic use*; D017698:Postmenopause; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D011960:Receptors, Estrogen / Q000032:analysis; D013629:Tamoxifen / Q000009:adverse effects / Q000627:therapeutic use*; D014230:Triazoles / Q000009:adverse effects / Q000627:therapeutic use*
D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D011960:Receptors, Estrogen; D014230:Triazoles; D013629:Tamoxifen; D000077384:Anastrozole