Trial Information

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.