Antiandrogen withdrawal alone or in combination with ketoconazole in androgen-independent prostate cancer patients: a phase III trial (CALGB 9583)

Progress in detection and treatment of prostate cancer

PURPOSE OF REVIEW

The purpose of this review is to highlight the most important developments in the diagnosis, prevention, and management of prostate cancer reported in the past year that have been published in the medical literature.

RECENT FINDINGS

Recent research has shown that clinically meaningful prostate cancer can develop in patients with a PSA value <4 ng/dL and has suggested that 'watchful waiting' approaches may not be appropriate for young patients or those with a life expectancy of greater than 15 years. The contribution of obesity to high-grade disease and a higher rate of relapse has also been described. There is now randomized data suggesting that adjuvant hormonal therapy for as little as six month's time confers a survival benefit for those receiving radiation therapy. Secondary hormonal manipulation with ketoconazole is now supported by randomized phase III data. Most importantly, this year the results of two randomized phase III clinical trials of chemotherapy in hormone refractory prostate cancer have shown that survival can be increased by 20% with the use of docetaxel.

SUMMARY

Recent data reported in the past year have significant implications for those involved in the management of prostate cancer. The results of the chemotherapy trials have resulted in new standards of care for this disease.

Reappraisal of the Concept of Hormone Therapy in Metastatic Prostate Cancer and Implications for Treatment

Almost all prostate cancer patients become resistant to hormonal therapy that blocks androgen-mediated cell proliferation. The key to this resistance may lie in expression of the androgen receptor itself. Alternative methods to block the AR-mediated signaling pathways appear to be critical for tumor survival. These signal transduction pathways that interact with AR may enhance the response to androgen ablation therapy. The identification of signaling pathways may be a major goal in the treatment of prostate cancer. The application of novel therapies must be preceded by the identification of the genetic and molecular tumor profiles for each patient.

Chemotherapy for advanced prostate cancer: Results of new clinical trials and future studies

Our understanding of the role of chemotherapy for advanced prostate cancer has improved considerably in 2004 with the publication of two large randomized phase III trials and the approval by the US Food and Drug Administration of docetaxel and prednisone for metastatic hormone-refractory disease. Although treatment is still considered palliative in nature, studies of chemotherapy for metastatic hormone-refractory prostate cancer (HRPC) have demonstrated improved overall survival compared with older regimens as well as clinically significant improvements in important endpoints, such as quality of life and time to progression. In particular, docetaxel has emerged as first-line therapy on an every-3-week schedule for metastatic HRPC, replacing mitoxantrone, as recently reported in the TAX327 trial. Docetaxel and estramustine combinations have the disadvantage of significant cardiovascular and gastrointestinal toxicity, and further use of estramustine is likely unwarranted as first-line therapy. Future trials examining novel biologic agents and combination therapies should use single-agent docetaxel as the reference standard. The role of chemotherapy for advanced disease in the neoadjuvant or adjuvant setting, in biochemically (PSA) relapsed patients, and as second-line therapy for relapsed disease, remains a subject of active clinical investigation.

Secondary hormonal manipulations in prostate cancer

Virtually all patients treated with androgen deprivation eventually develop progressive clinical or biochemical disease despite this therapy. Despite low levels of androgen, the androgen receptor remains active, making secondary hormonal therapies a reasonable clinical approach. Considerations for such patients include antiandrogen withdrawal, sequential use of antiandrogens, adrenal cortex inhibitors, and estrogenic compounds. Collectively, the modest activity of these therapies challenges the notion that advancing prostate cancer will uniformly become "hormone refractory."

Future therapies in hormone-refractory prostate cancer

Hormone-refractory prostate cancer (HRPC) remains true to its name: it is largely refractory to attempts to delay its progression. Although the number of men presenting with metastatic prostate cancer has decreased significantly over the last several years, the death rate for those men is essentially unchanged. To alter the currently inevitable progression of HRPC to death, new targets and new therapies are needed. This article reviews investigational therapies directed against standard targets (eg, the hypothalamic-pituitary-gonadal axis) as well as novel targets (eg, the endothelin axis).

Multidisciplinary management of advanced prostate cancer: Changing perspectives on referring patients and enhancing collaboration between oncologists and urologists in clinical trials

Prostate cancer traditionally was managed by monotherapy, and treatment was almost exclusively provided by the urologic surgeon. As ongoing clinical trials in advanced disease identify novel agents or combination therapies with good tolerability and potential survival benefits, multidisciplinary management may offer optimal care for men with high-risk prostate cancer, as it does for women with breast cancer. Patients with high-risk recurrent or metastatic disease should be informed of clinical trials for which they may be eligible.

A randomized, phase II trial of ketoconazole plus alendronate versus ketoconazole alone in patients with androgen independent prostate cancer and bone metastases

PURPOSE

Alendronate (AL), a potent oral bisphosphonate, blocks the secretion of matrix metalloproteinase-2 and the establishment of bone metastases in animal models. Ketoconazole (KT) has demonstrated activity in androgen independent prostate cancer (AIPC). In this study we determined whether KT plus AL produced acceptable disease responses compared with KT alone. As the experimental design, 72 patients with progressive AIPC metastatic to bone were randomized to receive KT (1,200 mg daily) plus hydrocortisone (H) (30 mg daily) with or without AL (40 mg daily). Prostate specific antigen (PSA) consensus criteria and radiographic scans were used to determine the proportion of patients with a PSA decrease, time to progression and response duration. The pharmacokinetics of KT and AL were characterized and changes in circulating angiogenic factors were assessed.

RESULTS

At a median potential followup of 23.9 months the proportion of patients with a greater than 50% decrease in PSA was similar in the KT/H/AL and KT/H, groups (50% and 47%, respectively). The median duration of response was 8.9 and 6.3 months in the KT/H/AL and KT/H groups, respectively (p = 0.125). Median progression-free survival was not significantly prolonged in the KT/H/AL group (4.6 vs 3.8 months, p = 0.27). There was no significant difference in overall survival between the 2 treatment arms but there was a trend toward improved survival in the KT/H arm (p = 0.074). Toxicity in the 2 groups was mild and there were no clear associations between changes in circulating angiogenic factor levels and clinical outcomes in either treatment arm.

CONCLUSIONS

There were no statistically significant differences in response rate, progression-free survival or overall survival between KT/H alone and KT/H plus AL treatment in patients with AIPC. The addition of AL to KT/H may increase the response duration with an acceptable safety profile compared with treatment with KT/H alone. However, the addition of AL offers no survival benefit in patients with AIPC.

Second-Line Chemotherapy for Hormone-Refractory Prostate Cancer: Has the Time Come?

Prostate-specific antigen testing has not only led to an earlier diagnosis of prostate cancer, but also to an earlier identification of hormone-refractory prostate cancer (HRPC). Many patients identified early with HRPC may receive first-line taxane-based chemotherapy. Patients who progress after first-line chemotherapy are still quite healthy and desire further therapy. No proven treatment options exist for the second-line treatment of HRPC. Finding new agents that are active in the second-line setting and identifying relevant outcome variables and predictive pretreatment variables are crucial in improving survival and quality of life for this patient population.

Society of Urologic Oncology position statement: Redefining the management of hormone-refractory prostate carcinoma

Because patients with hormone-refractory prostate carcinoma are a very diverse group, management of these patients represents a unique challenge. Despite much research, to the authors' knowledge few studies published to date have provided definitive treatment answers. The Society of Urologic Oncology (SUO) convened a multidisciplinary panel of urologists, oncologists, and radiation oncologists to develop a treatment algorithm for patients with hormone-refractory prostate carcinoma. The resulting treatment outline was based on a review of the literature review and on the expert opinions of the panelists. The current article provided a logical progression of treatment choices that included hormonal manipulations, chemotherapeutic options, and adjunctive therapies. Future clinical trials and therapies were also discussed by the authors. Management strategies should be targeted toward the individual patient. Although significant progress has been made in understanding and treating hormone-refractory prostate carcinoma, earlier interventions would be ideal and better therapeutic approaches to prolong survival are necessary.

Role of secondary hormonal therapy in the management of recurrent prostate cancer

Androgen ablation remains the cornerstone of the systemic management of prostate cancer. After initial androgen deprivation, clinical outcomes vary considerably. For the patient with progressive disease after androgen deprivation, multiple therapeutic options are available and include antiandrogen withdrawal, chemotherapy, and secondary hormonal agents. Multiple secondary hormonal agents have clinical activity and the sequential use of these agents may lead to prolonged periods of clinical response. In addition to the use of oral antiandrogens, active secondary hormonal therapies include adrenolytic agents such as ketoconazole and aminoglutethimide, corticosteroids and estrogenic compounds. This article reviews the clinical trial data for these various agents and discusses their role in the management of patients with advanced prostate cancer.