Double-blind randomised trial comparing the non-steroidal aromatase inhibitors letrozole and fadrozole in postmenopausal women with advanced breast cancer.
BACKGROUND
To compare the efficacy, safety and tolerability of letrozole, an advanced non-steroidal aromatase inhibitor, and fadrozole hydrochloride, an older-generation drug in this class, we conducted a randomised double-blind trial in postmenopausal women with advanced breast cancer.


METHODS
One hundred and fifty-seven postmenopausal women with advanced breast cancer were enrolled and randomly assigned to receive letrozole or fadrozole in a multicentre, randomised double-blind trial in Japan. One hundred and fifty-four eligible patients were treated with either letrozole 1.0 mg once daily (n = 77) or fadrozole 1.0 mg twice daily (n = 77), for a minimum of 8 weeks.


RESULTS
Letrozole showed a significantly higher overall objective response rate [complete response (CR) + partial response (PR)] than fadrozole (31.2% and 13.0%, respectively; P = 0.011, Fisher's exact test). Clinical benefits defined as CR, PR and stable disease (no change in status for more than 24 weeks) were also higher in patients treated with letrozole (50.6%) than fadrozole (35.1%). Letrozole was significantly superior to fadrozole in terms of the dominant lesion in soft tissue, bone and viscera (P = 0.011, stratified Mantel-Haenszel test). Median time to progression was 211 days in the letrozole group and 113 days in the fadrozole group with no significant difference (P = 0.175, log-rank test). Letrozole markedly reduced the estradiol, estrone and estrone sulfate levels in peripheral blood within 4 weeks. The suppressive effect of fadrozole on these hormone levels was insufficient. Adverse drug reactions were observed in 35.9% of the patients treated with letrozole and in 39.5% of those treated with fadrozole with no significant difference between the two groups (P = 0.74, Fisher's exact test). Most of the adverse drug reactions were rated as grade 1 or 2.


CONCLUSIONS
The results show letrozole at a dose of 1.0 mg once daily to be more effective in treating postmenopausal women with advanced breast cancer than fadrozole at 1.0 mg twice daily, with similar safety and tolerability profiles.
Tominaga
T
T
Breast Cancer Center, Toyosu Hospital, Showa University School of Medicine, Tokyo, Japan. t-tominaga@hkg.odn.ne.jp
Adachi
I
I
Sasaki
Y
Y
Tabei
T
T
Ikeda
T
T
Takatsuka
Y
Y
Toi
M
M
Suwa
T
T
Ohashi
Y
Y
D000284:Administration, Oral; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D047072:Aromatase Inhibitors; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D004311:Double-Blind Method; D004791:Enzyme Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D004958:Estradiol / Q000097:blood; D004970:Estrone / Q000031:analogs & derivatives* / Q000097:blood; D017316:Fadrozole / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D000077289:Letrozole; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D009570:Nitriles / Q000009:adverse effects / Q000627:therapeutic use*; D017698:Postmenopause; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012449:Safety; D015996:Survival Rate; D014230:Triazoles / Q000009:adverse effects / Q000627:therapeutic use*
D000970:Antineoplastic Agents; D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D009570:Nitriles; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D014230:Triazoles; D004970:Estrone; D004958:Estradiol; D000077289:Letrozole; D017316:Fadrozole; C017296:estrone sulfate