Higher doses of mitoxantrone among men with hormone-refractory prostate carcinoma: a Cancer and Leukemia Group B study

Hormone Refractory Prostate Cancer (Hrpc): Present and Future Approaches of Therapy

The mainstay of therapy for patients with advanced prostate cancer still remains androgen deprivation, although response to this is invariably temporary. Most of the patients develop hormone-refractory disease resulting in progressive clinical deterioration and, ultimately, death. Until recently there has been no standard chemotherapeutic approach for hormone refractory prostate cancer (HRPC), the major benefits of chemotherapy being only palliative. The studies combining mitoxantrone plus a corticosteroid demonstrated that chemotherapy could be given to men with symptomatic HRPC with minimal toxicity and a significant palliation could be provided. Recently, results from 2 phase III randomized clinical trials demonstrating that a combination of docetaxel plus prednisone can improve survival in men with HRPC have propelled docetaxel-based therapy into the forefront of treatment options for these patients as the new standard of care. There is a promising activity of new drug combinations such as taxanes plus vinca alkaloids; bisphosphonates are assuming a prominent role in prostate therapy through their ability to prevent skeletal morbidity. Combinations of classic chemotherapeutic agents and biological drugs began to be tested in phase II-III trials and the first results appear interesting. This article focuses on combinations recently evaluated or under clinical development for the treatment of HRPC.

Is There a Standard Chemotherapeutic Regimen for Hormone-Refractory Prostate Cancer? Present and Future Approaches in the Management of the Disease

Prostate cancer that no longer responds to hormonal manipulation can be defined as hormone-refractory prostate cancer. Until recently, there has been no standard chemotherapeutic approach for hormone-refractory prostate cancer. The major benefits of chemotherapy in the treatment of the disease are palliative in nature, in terms of reduction of pain and use of analgesics and improvement of performance status, as followed in the most recent trials. Phase III studies are necessary to better evaluate the efficacy of the different regimens, because several old studies suffer for methodological deficits. There is a promising activity of new drug combinations, such as vinca alkaloids and taxanes. Phase I and II trial are testing combinations of classic chemotherapeutic agents and biologic drugs, and the first results appear interesting. In this article, recent advances in the treatment of hormone-refractory prostate cancer using chemotherapeutic regimens are critically reviewed.

Treatment Options in Hormone-refractory Metastatic Prostate Carcinoma

Prostate cancer represents one of the most important health problems in industrialized countries. It is the second leading cause of cancer-related death in the United States. Therapeutic options are different according to the stage of the disease at the diagnosis. Patients with localized disease may be treated with surgery or radiation, whereas the treatment for patients with a metastatic disease is purely palliative. Hormonal treatment represents the standard therapy for stage IV prostate cancer, but patients ultimately become unresponsive to androgen ablation and are classified as hormone-refractory prostate cancer patients. The molecular mechanisms involved in progression in hormone resistance are characterized by mutations, down and up-regulation in the androgen receptor gene, mutations in p53 and over-expression of Bcl2 and other alterations in genes and in gene expression. The important thing is that we understand these mechanisms to define potential therapeutic agents for the treatment of hormone-refractory prostate cancer patients. Conventional options for patients with hormone-refractory prostate cancer include secondary hormone therapy, radiotherapy and cytotoxic chemotherapy. The commonest antineoplastic agents are mitoxantrone, estramustine and taxanes. Despite an improvement In the palliative benefit, none of these agents has demonstrated a beneficial impact on the overall survival of patients. Therefore, there is no standard therapy for these patients, thus we need new approaches which should be studied in clinical trials. The evaluation and incorporation of new agents into current treatment regimens could have a role in the treatment of hormone-refractory prostate cancer, but their efficacy has not yet been demonstrated.

Postoperative radiotherapy and mitoxantrone for anal sac adenocarcinoma in the dog: 15 cases (1991-2001)

The medical records of 15 dogs with anal sac adenocarcinoma (ASAC) treated with concurrent curative-intent radiotherapy and mitoxantrone (MX) after surgical removal of the primary tumour were reviewed retrospectively. Radiation was prescribed at 15 daily fractions of 3.2 Gy for a total dose of 48 Gy. MX was given intravenously at a dosage of 5 mg m(-2) every 3 weeks for five treatment sessions. Twelve dogs received pelvic irradiation to include the regional lymph nodes (LNs) and three received radiation only to the perineum. At the time of diagnosis, four dogs were hypercalcaemic and seven dogs presented with regional LN metastasis. All the dogs with regional LN metastasis received pelvic irradiation, and in three cases, metastatic LNs were treated in the macroscopic disease setting. The median event-free survival was 287 days, and the median overall survival was 956 days. Acute and chronic radiation complications were common and non-life threatening, although chronic complications contributed to the decision to euthanize two dogs. The results observed in this retrospective analysis compare favourably with cases of ASAC in the literature related to treatment with surgery and/or chemotherapy.

Progression-free survival as a predictor of overall survival in men with castrate-resistant prostate cancer

PURPOSE

To explore whether progression-free survival (PFS) or biochemical PFS can be used as a predictor of overall survival (OS) and to investigate the dependence between PFS and OS in men with castrate-resistant prostate cancer.

PATIENTS AND METHODS

Data from nine Cancer and Leukemia Group B trials that enrolled 1,296 men from 1991 to 2004 were pooled. Men were eligible if they had prostate cancer that had progressed during androgen deprivation therapy and did not receive prior treatment with chemotherapy, immunotherapy, or other nonhormonal therapy. Landmark analyses of PFS at 3 and 6 months from randomization/registration were performed to minimize lead time bias. The proportional hazards model was used to assess the significance effect of PFS rate at 3 and at 6 months in predicting OS. In addition, biochemical progression using the definitions of Prostate-Specific Antigen Working Group (PSAW) Criteria PSAWG1 and PSAWG2 were analyzed as time-dependent covariates in predicting OS.

RESULTS

The median survival time among men who experienced progression at 3 months was 9.2 months (95% CI, 8.0 to 10.0 months) compared with 17.8 months in men who did not experience progression at 3 months (95% CI, 16.2 to 20.4 months; P < .0001). Compared with men who did not progress at 3 and at 6 months, the adjusted hazard ratios for death were 2.0 (95% CI, 1.7 to 2.4; P < .001) and 1.9 (95% CI, 1.6 to 2.4; P < .001) for men who experienced progression at 3 and 6 months, respectively. In addition, biochemical progression at 3 months predicted OS. The association between PFS and OS was 0.30 (95% confidence limits = 0.26, 0.32).

CONCLUSION

PFS at 3 and 6 months and biochemical progression at 3 months predict OS. These observations require prospective validation.

Assessing outcomes in prostate cancer clinical trials: a twenty-first century tower of Babel

BACKGROUND

Because of the osseous distribution of prostate cancer metastases, progression is more readily identified than response in prostate cancer clinical trials. As a result, there is an increased focus on progression-free survival (PFS) as a phase 2 endpoint. PFS, however, is vulnerable to inter-study design variability. The authors sought to identify and quantify this variability and the resultant error in PFS across prostate cancer clinical trials.

METHODS

The authors reviewed phase 2 clinical trials of cytotoxic agents in castration-resistant metastatic prostate cancer over 5 years to evaluate the policies determining extent of disease and the definitions of disease progression. A simulation model was created to define the degree of error in estimating PFS in 3 hypothetical cohorts (median PFS of 12, 24, and 36 weeks) when the frequency of outcome assessments varies.

RESULTS

Imaging policies for trial entry were heterogeneous, as were the type, timing, and indications for outcome assessments. In the simulation, error in the reported PFS varied according to the interval between assessments. The difference between the detected and the true PFS could vary as much as 6.4 weeks per cycle, strictly resulting from the variability of assessment schedules tested.

CONCLUSIONS

Outcome assessment policies are highly variable in phase 2 studies of castration-resistant prostate cancer patients, despite published guidelines designed to standardize authentication of disease progression. The estimated error in PFS can exceed 6 weeks per cycle, exclusively because of variations in the assessment schedules. Comparisons of PFS times from different studies must be made with circumspection.

Predictors of prostate cancer tissue acquisition by an undirected core bone marrow biopsy in metastatic castration-resistant prostate cancer--a Cancer and Leukemia Group B study

PURPOSE

Analyzing metastatic prostate cancer tissue is of considerable importance in evaluating new targeted agents, yet acquiring such tissue presents a challenge due to the predominance of bone metastases. We assessed factors predicting a successful tumor harvest from bone marrow biopsies (BMBx) in castration-resistant metastatic prostate cancer patients.

MATERIAL AND METHODS

Data from Cancer and Leukemia Group B study 9663 were reviewed. Bone marrow biopsies were obtained from 184 patients who underwent an office-based, unguided bone marrow biopsy of the posterior iliac crest.

RESULTS

Forty-seven of the 184 patients (25.5%) had a positive bone marrow biopsy. When considered in a multivariate logistic regression analysis, lower hemoglobin levels, higher alkaline phosphatase, and higher lactate dehydrogenase levels were associated with a higher likelihood of a positive BMBx. The median survival time was 11 months (95% confidence interval, 8.0-14) among patients with a positive BMBx compared with 23 months (95% confidence interval, 19-27) with a negative BMBx. The median time to progression and time to prostate-specific antigen progression-free survival were also significantly decreased among positive BMBx patients. No patients with a positive BMBx survived beyond 3 years, whereas 11 of the 137 patients with a negative BMBx survived beyond 5 years.

DISCUSSION

Using common laboratory values, a specific patient cohort can be defined from whom the yield of a nonguided BMBx would be high enough to justify this approach. For studies that require broader entry criteria, a more directed approach with image guidance is recommended.

A modified low-dose regimen of mitoxantrone and prednisolone in patients with androgen-independent prostate cancer

BACKGROUND

We conducted this retrospective study to analyze a modified dose schedule of mitoxantrone and prednisolone (MP) in patients with androgen-independent prostate cancer.

METHODS

From June 1997 to April 2002, 28 patients were enrolled. Their median age was 69 years (range, 58-79 years). The median duration of hormonal therapy was 30 months (range, 6-84 months). The median performance status was 2. Sixteen of the patients had bone disease only. The chemotherapy consisted of 8 mg/m2 mitoxantrone by intravenous infusion every 3 weeks and 10 mg prednisolone orally twice per day. WHO response criteria, prostatic-specific antigen (PSA), pain and performance status were used to assess the response.

RESULTS

The median number of treatment cycles was six (range, 2-20). Nine (32.1%) and 15 patients (53.8%) had > or =80% and > or =50% reduction in serum PSA level, respectively. Of 16 patients using narcotics, five (31.3%) had a > or =50% reduction in narcotics consumption compared with the baseline. Nine patients (32.1%) showed improved performance. For 12 patients with measurable disease, only two (16.7%) showed a partial response. Grade 3-4 toxicities included neutropenia (three patients), anemia (three patients) and vomiting (one patient). The median survival was 12 months and the median time to PSA progression was 4 months.

CONCLUSIONS

This modified regimen is feasible for palliative intent. The toxicity of this regimen is manageable. Exploring further combinations of this regimen with novel agents against androgen-independent prostate cancer is warranted.

Phase II study of vinorelbine and low-dose docetaxel in chemotherapy-naive patients with hormone-refractory prostate cancer

PURPOSE

Vinorelbine, a semisynthetic vinca alkaloid, and docetaxel, a semisynthetic taxane, are active single agents in hormone-refractory prostate cancer and have demonstrated synergy in tumor cell lines and animal models. This study was designed to assess the efficacy and tolerability of vinorelbine and low-dose docetaxel in chemotherapy-naive, hormone-refractory prostate cancer patients whose disease had progressed after withdrawal from anti-androgens, despite castrate testosterone levels.

PATIENTS AND METHODS

Patients with histologically confirmed hormone-refractory prostate cancer despite testosterone levels < or = 50 ng/mL, Karnofsky performance status > 70, and adequate bone marrow reserve were enrolled. They received vinorelbine, 20 mg/m2, followed by docetaxel, 25 mg/m2, on days 1 and 8 of a 21-day cycle. Tumor response was defined by prespecified reductions from baseline prostate-specific antigen levels or bidimensionally measurable disease. Adjustments in the dose of either agent were based on > or = grade 2 toxicity according to standard criteria.

RESULTS

Twenty-one patients with a mean age of 76 years (range, 60-83 years) and a median prostate-specific antigen level of 116 ng/mL (range, 10.4-4,262 ng/mL) were enrolled and received a total of 152 courses (median, 7.5 courses) of vinorelbine and docetaxel. Of the 19 patients who were evaluable for biochemical response, prostate-specific antigen reductions from baseline of > 75%, > or = 50% to < or = 75%, and < 50% were observed in eight, three, and seven patients, respectively (median prostate-specific antigen decrease, 60% +/- 31%). Of five patients with measurable disease, three were evaluable: one patient had a complete response, and two had partial responses at the site of measurable disease. The vinorelbine/docetaxel doublet was generally well tolerated. In the first two cycles of therapy, six patients had grade 3 and eight patients had grade 4 neutropenia as their worst-grade toxicities; all cases were manageable with granulocyte colony stimulating factor support. Acute respiratory distress syndrome was observed in one patient. There were few dose reductions or interruptions.

DISCUSSION

Vinorelbine, 20 mg/m2, and low-dose docetaxel, 25 mg/m2, given on days 1 and 8 every 21 days, is a well-tolerated regimen with biochemical and objective response rates comparable to standard therapies in patients with hormone-refractory prostate cancer. A multicenter, randomized trial is under way to compare vinorelbine plus low-dose docetaxel with estramustine plus higher-dose docetaxel (60 mg/m2).

Prognostic model for predicting survival in men with hormone-refractory metastatic prostate cancer

PURPOSE

To develop and validate a model that can be used to predict the overall survival probability among metastatic hormone-refractory prostate cancer patients (HRPC).

PATIENTS AND METHODS

Data from six Cancer and Leukemia Group B protocols that enrolled 1,101 patients with metastatic hormone-refractory adenocarcinoma of the prostate during the study period from 1991 to 2001 were pooled. The proportional hazards model was used to develop a multivariable model on the basis of pretreatment factors and to construct a prognostic model. The area under the receiver operating characteristic curve (ROC) was calculated as a measure of predictive discrimination. Calibration of the model predictions was assessed by comparing the predicted probability with the actual survival probability. An independent data set was used to validate the fitted model.

RESULTS

The final model included the following factors: lactate dehydrogenase, prostate-specific antigen, alkaline phosphatase, Gleason sum, Eastern Cooperative Oncology Group performance status, hemoglobin, and the presence of visceral disease. The area under the ROC curve was 0.68. Patients were classified into one of four risk groups. We observed a good agreement between the observed and predicted survival probabilities for the four risk groups. The observed median survival durations were 7.5 (95% confidence interval [CI], 6.2 to 10.9), 13.4 (95% CI, 9.7 to 26.3), 18.9 (95% CI, 16.2 to 26.3), and 27.2 (95% CI, 21.9 to 42.8) months for the first, second, third, and fourth risk groups, respectively. The corresponding median predicted survival times were 8.8, 13.4, 17.4, and 22.80 for the four risk groups.

CONCLUSION

This model could be used to predict individual survival probabilities and to stratify metastatic HRPC patients in randomized phase III trials.