@article {ONISHI2999, author = {TAKEHISA ONISHI and TAKUJI SHIBAHARA and SATORU MASUI and YUSUKE SUGINO and SHINICHIRO HIGASHI and TAKESHI SASAKI}, title = {Efficacy of Ethinylestradiol Re-challenge for Metastatic Castration-resistant Prostate Cancer}, volume = {36}, number = {6}, pages = {2999--3004}, year = {2016}, publisher = {International Institute of Anticancer Research}, abstract = {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. Patients and 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. Conclusion: 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.}, issn = {0250-7005}, URL = {https://ar.iiarjournals.org/content/36/6/2999}, eprint = {https://ar.iiarjournals.org/content/36/6/2999.full.pdf}, journal = {Anticancer Research} }