Efficacy of Ethinylestradiol Re-challenge for Metastatic Castration-resistant Prostate Cancer.
BACKGROUND
There has recently been renewed interest in the use of estrogens as a treatment strategy for castration-resistant prostate cancer (CRPC). The purpose of this study was to evaluate the feasibility and efficacy of ethinylestradiol re-challenge (re-EE) in the management of CRPC.


METHODS
Patients with metastatic CRPC who received re-EE after disease progression on prior EE and other therapy were retrospectively reviewed for prostate-specific antigen (PSA) response, PSA progression-free survival (P-PFS) and adverse events.


RESULTS
Thirty-six re-EE treatments were performed for 20 patients. PSA response to the initial EE treatment was observed in 14 (70%) patients. PSA response to re-EE was 33.3% in 36 re-EE treatments. The median P-PFS for patients treated with initial and re-EE was 7 months and 4 months, respectively. Interestingly, PSA response to re-EE was observed even in non-responders to initial EE, and those treated with multiple re-EE. No patients developed cardiovascular or thromboembolic events.


CONCLUSIONS
Re-EE may be safely repeated several times and can lead to a prolonged disease control in selected patients. Re-challenge with EE appears to be a reasonable option worth considering for patients with metastatic CRPC.
Department of Urology, Ise Red Cross hospital, Ise, Japan takehisa@ise.jrc.or.jp.
Takehisa
T
Onishi
Department of Urology, Ise Red Cross hospital, Ise, Japan.
Takuji
T
Shibahara
Department of Urology, Ise Red Cross hospital, Ise, Japan.
Satoru
S
Masui
Department of Urology, Ise Red Cross hospital, Ise, Japan.
Yusuke
Y
Sugino
Department of Urology, Ise Red Cross hospital, Ise, Japan.
Shinichiro
S
Higashi
Department of Urology, Mie University Graduate School of Medicine, Tsu, Japan.
Takeshi
T
Sasaki
D000368:Aged; D000369:Aged, 80 and over; D004997:Ethinyl Estradiol / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D009362:Neoplasm Metastasis; D017430:Prostate-Specific Antigen / Q000097:blood; D064129:Prostatic Neoplasms, Castration-Resistant / Q000097:blood / Q000188:drug therapy* / Q000473:pathology; D012189:Retrospective Studies
D004997:Ethinyl Estradiol; D017430:Prostate-Specific Antigen
Castration-resistant prostate cancer; ethinylestradiol; re-challenge