Chemotherapy for the treatment of hormone-refractory prostate cancer

AIMS

This review aims at analysing the published literature on chemotherapy for hormone-refractory prostate cancer (HRPC) to provide recommendations for the treatment of this important patient group.

METHODS

The information for this review was compiled using the PubMed and Medline databases and the Proceedings of the American Society of Clinical Oncology annual meetings to search for articles, abstracts and presentations up to 1 March 2007. Electronic early-release publications were also included. Only articles published in English were considered. The search terms included hormone-refractory prostate cancer, docetaxel, mitoxantrone, satraplatin, ixabepilone, cyclophosphamide, vinorelbine, atrasentan, calcitriol, bevacizumab and targeted therapies. Priority was given to studies in high impact factor journals when available.

RESULTS AND CONCLUSION

Two recent trials (TAX 327 and SWOG 9916) have shown that docetaxel chemotherapy can significantly improve survival for HRPC. Docetaxel has become the standard of care for first-line chemotherapy for HRPC and has been approved for use in the United States and Europe. Many patients with HRPC will require second- and even third-line treatment upon progression and more data are required in this setting. It is likely that the future management of patients with HRPC will build on the success of docetaxel using a sequence of chemotherapy and targeted therapies to reduce the risk of death, prevent or improve disease-related symptoms and improve quality of life for this important condition.

Weekly high-dose calcitriol and docetaxel in patients with metastatic hormone-refractory prostate cancer previously exposed to docetaxel

OBJECTIVE

To evaluate the activity and tolerability of weekly high-dose calcitriol and docetaxel in patients with metastatic hormone-refractory prostate cancer (HRPC) previously exposed to docetaxel, as patients who progress after docetaxel treatment might be considered for second-line chemotherapy, but with no standard salvage therapy available we hypothesised that high-dose calcitriol might restore sensitivity to chemotherapy.

PATIENTS AND METHODS

The study comprised 26 patients who had progressed after first-line treatment with docetaxel-based chemotherapy had failed. Treatment cycles consisted of calcitriol (32 microg orally as 0.5 microg tablets) on day 1 and docetaxel (30 mg/m(2) intravenous) on day 2, administered for six consecutive weeks followed by a 2-week rest interval for a maximum of 24 cycles.

RESULTS

There was a response in prostate-specific antigen (PSA) level in eight patients (31%); seven (27%) had a stable PSA level for >/= 12 weeks. The median time to PSA progression was 4.2 months and the median survival was 9.3 months. The regimen was generally well tolerated; there was grade 2 hypercalcaemia, probably related to calcitriol, in one patient after six treatment cycles.

CONCLUSION

Weekly high-dose calcitriol and docetaxel seems to be an effective and well-tolerated treatment option for patients with metastatic HRPC previously exposed to docetaxel-based chemotherapy.

Efficacy and safety of single-agent pertuzumab (rhuMAb 2C4), a human epidermal growth factor receptor dimerization inhibitor, in castration-resistant prostate cancer after progression from taxane-based therapy

PURPOSE

Pertuzumab represents a new class of targeted anticancer agents, human epidermal growth factor receptor (HER) dimerization inhibitors. The aim of this single-arm phase II clinical study was to assess the efficacy and safety of single-agent pertuzumab in castration-resistant prostate cancer (CRPC) patients who had experienced progression after prior chemotherapy.

PATIENTS AND METHODS

Patients received pertuzumab every 3 weeks. All castration-resistant patients had experienced progression after at least one taxane-based regimen. Patients received a loading dose of 840 mg pertuzumab (cycle 1) followed by 420 mg for subsequent cycles. The primary end point was overall response and safety. A separate retrospective analysis of actual survival time versus predicted survival time for a patient population with comparable prognostic features was performed.

RESULTS

Patients were enrolled (N = 42) and treated (n = 41). No patients had complete or partial response (as defined by Response Evaluation Criteria in Solid Tumors Group or 50% decline in prostate-specific antigen). Of 30 efficacy-assessable patients, five had stable disease (SD) for at least 23 weeks; one of five had SD for 36 weeks. Pertuzumab was well tolerated; diarrhea was the most common adverse effect (61.0%, grades 1 to 3). Retrospective analysis of survival using a validated nomogram suggested that survival was prolonged with pertuzumab treatment, compared with historic controls with similar baseline prognostic features.

CONCLUSION

Pertuzumab was well tolerated and resulted in no objective responses, but several patients had SD more than 23 weeks from a heavily pretreated population. Retrospective analysis suggested prolonged median survival time with pertuzumab compared with historical controls. Thus, inhibition of HER dimerization may have clinical utility in CRPC patients.

Changing perspectives of the role of chemotherapy in advanced prostate cancer

The use of cytotoxic chemotherapy in advanced prostate adenocarcinoma has been validated by the recent demonstration of survival benefit in two large randomized phase III trials. Before publication of these landmark trials, SWOG 9916 and TAX 327, no chemotherapeutic regimen had shown survival benefit in the treatment of androgen independent prostate cancer (AIPC). These trials provide new encouragement for the use of chemotherapy in all stages of disease. Improved communication between medical and urologic oncologists and early patient referral for clinical trial participation remains essential for identifying new chemotherapeutic regimens with improved activity in AIPC and for defining the role of chemotherapy in earlier-stage disease. This article discusses the role of chemotherapy as the current standard of care for the treatment of AIPC and provides a historical perspective of the trials that preceded the development of current docetaxel-based regimens.

Management of Advanced Prostate Cancer After First-Line Chemotherapy

Hormone refractory prostate cancer (HRPC) causes substantial morbidity and mortality. There are increasing options for both first- and second-line therapy in the palliative treatment of patients with HRPC. Medications to control symptoms should first be optimized in patients with late-stage disease, and radiotherapy applied to dominant painful bone lesions. Docetaxel, mitoxantrone, satraplatin, and ixabepilone are active chemotherapeutic agents in the first- and/or second-line setting for patients with HRPC, and this may be true also of older drugs such as oral cyclophosphamide and vinorelbine. Radioisotopes such as strontium and samarium are useful for treatment of more generalized bone pain. Third-line hormonal maneuvers including glucocorticoids, ketoconazole, and estrogens can lead to further palliation in some patients, and there are provocative data that chemotherapy might restore hormonal sensitivity in a subset of patients.

Achieving Treatment Goals for Hormone‐Refractory Prostate Cancer with Chemotherapy

The belief that hormone-refractory prostate cancer (HRPC) is a chemotherapy-resistant disease has been effectively refuted by the results of two recent randomized phase III trials. The TAX327 trial compared weekly docetaxel, every-3-weeks (Q3W) docetaxel, and Q3W mitoxantrone plus prednisone in 1,006 patients with HRPC, and results demonstrated that survival was significantly longer with a docetaxel-based regimen than with mitoxantrone. That trial demonstrated that only Q3W docetaxel was significantly superior to mitoxantrone with respect to overall survival. Quality of life was also superior in the docetaxel groups. In the Southwest Oncology Group (SWOG) 9916 trial, 674 men with progressive HRPC were randomized to 3-week cycles of docetaxel plus estramustine or mitoxantrone plus prednisone. Overall and disease-free survival times were significantly longer in the docetaxel arm. Collectively, the results of these trials demonstrate that survival can be significantly improved with chemotherapy in patients with HRPC to an extent that is comparable with the survival benefits seen in other cancers considered sensitive to chemotherapy such as breast cancer. Among various research tasks in HRPC is the definition of potential surrogate end points for survival, which will facilitate the conduct of pivotal trials. Prostate-specific antigen (PSA) response rate and changes in PSA constructs (i.e., PSA doubling time and PSA velocity) are promising potential surrogate end points for future trials and are being actively evaluated at the present time. Until there is clear demonstration of a surrogate role for these alternative end points, survival remains the appropriate end point for phase III trials in HRPC. There is a need for safe and effective second- and third-line regimens for patients progressing after docetaxel, and these patients should enter clinical trials designed for this population. Mitoxantrone, vinorelbine, the platinum analogue satraplatin, and epothilone are among compounds that require careful testing in this setting. The addition of targeted therapies, such as the endothelin receptor antagonist, atrasentan, and angiogenesis inhibitors, such as thalidomide and bevacizumab, to docetaxel-based therapy is being evaluated. High-dose calcitriol may also be an effective addition to docetaxel. The extensive effort devoted to the evaluation of chemotherapy and other systemic modalities of treatment of HRPC is likely to yield additional clinical benefit for patients, making HRPC a more manageable, less lethal, and less debilitating disease.