Prostate-specific antigen testing in men with metastatic castration-resistant prostate cancer treated with docetaxel chemotherapy

Abstract

Since 2004, docetaxel chemotherapy has been reported to be effective and relatively safe in metastatic prostate cancer patients after failure with androgen deprivation therapy. 1,2 Not only prolonging survival, docetaxel chemotherapy has also benefits of relief of bony pain and improved quality of life. Using a standard 3weekly docetaxel regimen (75 mg/m 2 ), in the arm, 45% of patients had significant serum prostate-specific antigen (PSA) response (>50% reduction) with a median duration of 7.7 months; by contrast, patients using a 3-weekly mitoxantrone regimen, in the arm,hada32%PSAresponsewithamediandurationof7.8 months. 1 Similarly, Kellokumpu-Lehtinen et al, 3 reported in the Lancet Oncology that a 2-weekly docetaxel regimen (50 mg/m 2 ) had 49% PSA response while a standard 3-weekly docetaxel regimen had 42% PSA response. Moreover, docetaxel chemotherapy can also prolong the patients' overall survival in high-volume hormone-sensitive metastatic prostate cancer. 4 Despite these promising data, there is a lack of ideal markers predicting for disease-specific survival or overall survival. Currently, there is no clear consensus regarding the optimum duration or response predictors of chemotherapy for metastatic castrate-resistant prostate cancer (mCRPC) patients. Despite this, several small cohorts explored the prognostic significance of PSArelated parameters in mCRPC patients. Thomas et al 5 reported in a cohort of 41 consecutive mCRPC patients treated with 3-weekly docetaxel chemotherapy that time to PSA nadir of <16 weeks is an independent unfavorable predictor for response duration and progression-free survival. These findings were consistent with those in the articles by professor Huang's group. 6,7 Interestingly, Huang et al 7 reported in a large cohort of 650 patients with advanced or metastatic prostate cancer treated with androgen deprivation therapy (ADT) that the time to PSA nadir is an independent prognostic predictor for disease progression. Although the real mechanism is unclear, the author thought it may reflect a complicated role of androgeneandrogen receptor axis in prostate cancer. Indeed, recent studies also demonstrated that the development of lethal prostate cancer is also a dynamics process that follows the Darwinian evolutionary rule.