Efficacy of exemestane after nonsteroidal aromatase inhibitor use in metastatic breast cancer patients.
BACKGROUND
Previous studies have suggested a lack of complete cross-resistance between steroidal (exemestane) and non-steroidal aromatase inhibitors (nSAI).


METHODS
Eighty-eight metastatic breast cancer (MBC) patients who received 25 mg of exemestane orally once a day at the National Cancer Center, Korea, between 2003 and 2009, were reviewed retrospectively. All patients had received nSAI for metastatic disease prior to exemestane therapy.


RESULTS
The median age was 52 years (range, 33-79), and 13 (14.8%) patients were premenopausal who concomitantly received GnRH agonist. Exemestane was given as a second- (80.7%) or third-line (19.3%) hormone therapy. The clinical benefit (CB) rate (complete response + partial response + stable disease ≥ 24 weeks) was 30.7%, with a median CB duration of 10.0 months (range, 6.3-78.7). The median progression-free survival (PFS) was 3.0 months (95% confidence interval [CI], 1.99-4.01) and the overall survival (OS) 21.5 months (95% CI, 17.96-25.04), with a median follow-up of 50.3 months. Patients who achieved CB had longer OS than those patients who did not (29.6 vs 17.9 months; P = 0.002). On univariate analysis of predictive factors, patients who had achieved CB from previous nSAI tended to show lower CB rate (24.6% vs 44.4%, respectively; P = 0.063) and shorter PFS (2.8 vs 4.8 months, respectively; p = 0.233) than patients who had not. Achieving CB from previous nSAI became independent predictive factor for CBR to exemestane on multivariable analysis (Odds ratio = 2.852, P = 0.040).


CONCLUSIONS
Exemestane after nSAI failure was effective in prolonging CB duration. The drug's efficacy seemed to be inferior in patients who had benefit from previous nSAI use.
National Cancer Center, Goyang, Korea.
Sun Hye
SH
Kim
In Hae
IH
Park
Hyewon
H
Lee
Keun Seok
KS
Lee
Byung-Ho
BH
Nam
Jungsil
J
Ro
D000328:Adult; D000368:Aged; D000730:Androstadienes / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000401:mortality* / Q000473:pathology; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000188:drug therapy; D012189:Retrospective Studies
D000730:Androstadienes; D000970:Antineoplastic Agents; D047072:Aromatase Inhibitors; C056516:exemestane