Randomized Phase II Screening Trial of Docetaxel Plus Prednisolone With or Without Androgen Deprivation Treatment in Castrate-Resistant Prostatic Cancer

Androgen deprivation therapy (ADT) has been the mainstay in the treatment of metastatic prostate carcinoma. Despite initial favorable responses, predictable and irreversible resistance to ADT will occur in the vast majority of patients, which is defined as Castrate-Resistant prostate cancer (CRPC).

Recently, TAX327 study revealed docetaxel plus prednisolone could not only improve the QOL and PSA response but also prolong the survival in CRPC. It has been reasoned that discontinuation of ADT in nonorchiectomized patients may have detrimental effect on patients with CRPC as discontinuation of ADT can result in renewed release of testosterone and possible stimulation of remaining androgen-sensitive elements. When exogenous testosterone therapy is administered to patients with symptomatic CRPC, adverse responses can be induced. However, the lowest concentration of endogenous androgens that is capable of stimulating tumor growth is unknown. Data from animal models of androgen-dependent tumors showed that androgen-independent status is usually followed by androgen-insensitivity, which support the no need for ADT in CRPC. Contradictory, Dunning rat prostate cancer model cell lines, which are androgen-insensitive in vitro and grow slowly in the castrate rat, can grow more rapidly in a host with intact testis. In the retrospective observational study of CRPC treated with anthracycline, platinum, or ketoconazole, Taylor, et al. showed a modest, but statistically significant, survival advantage when ADT is continued. But, Hussain et al. and our team reported that there was no obvious advantage of continued ADT in response to cytotoxic chemotherapy or survival for in patients with CRPC. In addition, prospective trial conducted by Shamash, et al. showed that hormonal sensitivity can be reintroduced by stopping ADT during chemotherapy for CRPC. Among 43 patients who restarted androgen blockade after the completion of chemotherapy without ADT, 37% of patients had PSA response which was associated with survival advantage. Despite the limited and retrospective information available on the impact of continued ADT on disease outcome in CRPC when treated with cytotoxic chemotherapy, especially docetaxel containing regimen, ADT is frequently advocated to be used continuously. Considering little information on the benefit of continued ADT, and cost and side effects of ADT, prospective comparative studies are eagerly needed.