Serum prostate-specific antigen decline as a marker of clinical outcome in hormone-refractory prostate cancer patients: association with progression-free survival, pain end points, and survival

Endpoints in prostate cancer clinical trials

Prostate cancer is an extraordinarily heterogeneous disease with a variety of prognostic factors influential in determining ultimate patient outcomes. However, the vast majority of men harboring pathologic evidence of prostate cancer are not clinically diagnosed with this disease. Selected patients, particularly those with low clinical stage and low Gleason scores, may have extremely prolonged time until disease progression and cancer-specific death. Because of the potential for a prolonged natural history, factors, such as age and comorbidities, are often critical in evaluating clinical trial outcomes. Patients with more aggressive disease (higher clinical stage or Gleason score) have less prolonged natural histories. Careful examination of inclusion and exclusion criteria and the presence of clinical or pathologic staging are necessary for proper interpretation of clinical trials. Although surrogate endpoints, such as prostate-specific antigen and pathologic state, are commonly used to assess the effectiveness of therapeutic interventions, the relations between these surrogates and more relevant clinical endpoints have not always been well defined. Although certain endpoints are generalizable (overall survival and cancer-specific survival), clinical stage and treatments dictate the appropriateness of many other clinical trial endpoints. Both disease-related and treatment-related endpoints are important, given the propensity for various interventions to alter quality of life. Prospective randomized trials with adequate follow-up time and the assessment of clinically meaningful endpoints will offer the best opportunity to evaluate the effectiveness of various interventions used in this disease.

Receptor gene messenger RNA expression in metastatic lesions of prostate cancer

PURPOSE

There are hardly any options for treating hormone refractory prostate cancer. Some groups have already suggested antitumor therapy of prostate cancer using agonists, antagonists or other concepts acting on luteinizing hormone-releasing hormone (LH-RH) receptor. Few studies have been published to date on the detection of LH-RH receptors in human prostate cancer tissue. However, at this point it is completely unclear in this context whether metastasizing prostate cancer lesions, which may be major potential targets of a type of therapy, have any LH-RH receptors. In this study we examined tumor samples of lymph nodes from patients with prostate cancer obtained during radical prostatectomy and laparoscopic lymphadenectomy for the expression of LH-RH receptor messenger (m)RNA.

MATERIALS AND METHODS

Multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) was done to detect the expression of the mRNA of LH-RH receptor, prostate specific antigen and beta-actin in pelvic lymph nodes from 100 patients with prostate cancer.

RESULTS

In 27 patients at least 1 histopathological metastasis (19) and/or positive RT-PCR for prostate specific antigen (22) was identified. In 7 of these patients (25.9%) RT-PCR revealed LH-RH mRNA expression.

CONCLUSIONS

To our knowledge our study shows for the first time a rather low incidence of LH-RH receptor mRNA in primary pelvic lymph node metastases. However, since other studies show that an increased incidence of LH-RH receptors is typical of the hormone refractory stage of the disease, further studies in this specific patient population may help explain the clinical importance of LH-RH receptors in the development of new therapeutic approaches to advanced prostate cancer.

Randomized study of three different doses of suramin administered with a fixed dosing schedule in patients with advanced prostate cancer: results of intergroup 0159, cancer and leukemia group B 9480

PURPOSE

To test the hypothesis that the efficacy and toxicity of suramin in the treatment of patients with hormone-refractory prostate cancer was dose dependent.

PATIENTS AND METHODS

Patients were randomized with equal probability to receive low-, intermediate-, or high-dose suramin (total doses 3.192, 5.320, and 7.661 g/m(2), respectively). Overall survival, time to progression, and response rate (prostate-specific antigen [PSA] and objective) for each treatment arm were compared. Relationships between plasma suramin concentrations and response, toxicity, and survival were also evaluated.

RESULTS

Three hundred ninety patients were randomized. For the low-, intermediate-, and high-dose arms, the median survival time was 16, 14, and 13 months, respectively (P =.49). The objective response rate was 9%, 7%, and 15%, respectively (P =.10). PSA response rates were 24%, 28%, and 34%, respectively (P =.082). Landmark analyses of a 50% decline in PSA at 20 weeks showed a significant correlation with survival. There was a dose-response relationship between dose and toxicity. After adjusting for treatment arm, the measured suramin concentration was not associated with clinical response, PSA response, survival, or toxicity.

CONCLUSION

Although high-dose suramin was associated with higher objective and PSA response rates, these were not statistically significant. Overall, no dose-response relationship was observed for survival or progression-free survival, but toxicity was increased with the higher dose. Patients treated with the low-dose level experienced modest toxicity, making it the preferred arm on this study. The lack of a dose-response relationship and the toxicity profile observed raise questions regarding the utility of suramin, particularly high-dose suramin, as administered on this schedule.

Highlights of contemporary issues in the medical management of prostate cancer

This paper highlights contemporary issues in the medical management of prostate cancer. Controversies surrounding adjuvant and neo-adjuvant hormonal therapy in localized prostate cancer are reviewed, as well as the use of chemohormonal therapy in high risk localized disease. The latent period of asymptomatic biochemical progression prior to clinical progression is an opportunity to evaluate new non-toxic therapies. In patients with advanced metastatic disease hormonal therapy and new alternatives are discussed. Chemotherapy in hormone refractory prostate cancer (HRPC) is extensively covered as well as the emerging role of molecular-targeted therapies.

Prostate-specific antigen in prostate cancer: a case study in the development of a tumor marker to monitor recurrence and assess response

The serum marker known as prostate-specific antigen (PSA) has established itself as the most important tool for the early detection of prostate cancer. However, more recent data indicate that (post-treatment) PSA and PSA kinetics can be used to predict the outcome of a variety of therapeutic interventions including radical prostatectomy, radiation therapy, androgen deprivation, and treatment of hormone-refractory prostate cancer. PSA recurrence after radiation therapy is now accepted as a harbinger of developing metastatic disease. The American Society for Therapeutic Radiation Oncology (ASTRO) consensus definition is the most widely accepted definition of failure after radiation therapy. Rather than using a specific PSA cutoff, three consecutive PSA rises was felt to be a more reliable indicator of biochemical failure. The PSA nadir (the lowest PSA level achieved after therapeutic intervention) also appears to correlate with the likelihood of remaining disease-free. Similarly, a rapid doubling time is a significant predictor of developing distant metastases. The most appropriate definition for biochemical (PSA) failure following radical prostatectomy is usually considered to be a non-zero value. As is the case after radiotherapy, there appears to be a relationship between the rate of rise of the PSA and the risk of distant failure following radical prostatectomy. In patients with metastatic disease, multiple studies appear to indicate that a fall in PSA, however measured, appears to be predictive of improved outcome in prostate cancer patients treated with androgen deprivation. Multiple reports of trials in the treatment of hormone-refractory prostate cancer (HRPC) appear to substantiate the observation that patients who have a greater than 50% decline in PSA have an improved survival. Correlation of PSA declines with other markers of clinical benefit, including clinically significant "subjective" end points such as pain control, have strengthened the argument that a PSA decline can serve as an intermediate endpoint in clinical trials involving HRPC patients.

Novel Clinical Trials in Androgen-Independent Prostate Cancer

Current treatments for androgen-independent prostate cancer have not shown a definitive increase in survival. Several novel drugs have made their way through preclinical testing into early clinical trials. Targets discussed in this review include apoptosis, antiangiogenesis, growth factor receptors or associated tyrosine kinases, and tumor-associated antigens targeted by vaccines. Research in this area includes testing combinations of previously studied chemotherapeutic agents as well as identifying and testing novel agents. It is these drugs, either alone or in combination, that are designed to target strategic pathways to improve survival and increase quality of life in prostate cancer patients. This review focuses on the novel agents being tested with chemotherapy in metastatic prostate cancer.

Prostate cancer update

Recent advances in prostate cancer have focused on treatment strategies in patients with biochemical relapse and novel methods of androgen deprivation therapy such as intermittent therapy, the role of bisphosphonates, and immunotherapeutic approaches. Continued investigation into the mechanism of androgen independence and effective treatments for hormone-refractory disease are described. This article reviews the major advances in prostate cancer published between November 1, 2000, and October 31, 2001.

Treatment options in hormone-refractory prostate cancer: current and future approaches

Prostate cancer is the second leading cause of cancer mortality among men in Western countries. The initial treatment of advanced prostate cancer is suppression of testicular androgen production by medical or surgical castration, but nearly all men with metastases will develop disease progression. Patients with hormone refractory prostate cancer (HRPC) have a median survival of approximately 18 months and no therapy has yet demonstrated a definitive survival advantage. However, in the past several years, a number of promising new treatment strategies have emerged. One of the most important new treatment strategies involves secondary hormonal manipulation after the failure of primary androgen deprivation. This approach is predicated on the recognition that HRPC is a heterogeneous disease and some patients may respond to alternative hormonal interventions despite the presence of castrate levels of testosterone. Until recently, cytotoxic chemotherapy was felt to be relatively ineffective in the treatment of HRPC. Combination regimens incorporating new active agents have demonstrated significant activity in this setting, renewing interest in the use of chemotherapy to treat HRPC. Recent advances in the understanding of prostate cancer biology have led to the development of drugs directed against precise molecular alterations in the prostate tumour cell. Biologic agents now in development include those capable of altering signal transduction, blocking angiogenesis, inhibiting cell cycle progression, and stimulating apoptosis. In addition, many types of immune therapies are showing promise. Evaluating these agents, and incorporating them into existing regimens, are major goals of ongoing clinical research in advanced prostate cancer.