Change in serum prostate-specific antigen as a marker of response to cytotoxic therapy for hormone-refractory prostate cancer

Using splines to detect changes in PSA doubling times

BACKGROUND

PSA doubling time (PSADT) can predict the likelihood of clinical progression in patients with biochemical relapse after surgery or radiation for prostate cancer. Changes in PSA doubling time in response to therapy may be of clinical or investigational significance. How does one estimate PSADT before and after the initiation of therapy and determine if any change is statistically significant or simply the result of random variation? These are the type of questions addressed.

METHODS

Our technique uses a best-fitting spline (i.e., a broken-line approximation) to a graph of log PSA on time to estimate PSADTs before and after treatment initiation. A linear regression program is used to produce the fit and to evaluate the statistical significance of any change in PSADT. This method differs from previous methods in that it uses all the data, exploits the continuity of PSA at the time of treatment initiation, and allows one to make statistical significance statements about specific individuals.

RESULTS

Our technique is illustrated with data from a pilot clinical trial using a nutritional supplement in 12 men with prostate cancer. A detailed analysis of the first patient shows how the data are handled, how two lines of computer code are sufficient to fit the spline model, and how the doubling times and statistical significance of a change are read from the computer output. In the study, 9 of 12 patients had a statistically significant increase in doubling time. Because the study is preliminary and used only to illustrate our method, no medical discussion of the study is included. The last section of the study, in part expository, is devoted to explaining the underlying principles for those who may want to know not only what to do, but why it works.

CONCLUSIONS

The method presented here for determining changes in PSADT is both simple and broadly applicable. It allows the evaluation of the size and statistical significance of an observed change or increase in PSADT in response to therapy for prostate cancer. It can be done using essentially any statistical software and widely accepted statistical methods.

Biology of prostate-specific antigen

Prostate-specific antigen (PSA) is an androgen-regulated serine protease produced by both prostate epithelial cells and prostate cancer (PCa) and is the most commonly used serum marker for cancer. It is a member of the tissue kallikrein family, some of the members of which are also prostate specific. PSA is a major protein in semen, where its function is to cleave semenogelins in the seminal coagulum. PSA is secreted into prostatic ducts as an inactive 244-amino acid proenzyme (proPSA) that is activated by cleavage of seven N-terminal amino acids. PSA that enters the circulation intact is rapidly bound by protease inhibitors, primarily alpha1-antichymotrypsin, although a fraction is inactivated in the lumen by proteolysis and circulates as free PSA. This proteolytic inactivation, as well as the cleavage of proPSA to PSA, is less efficient in PCa. Serum total PSA levels are increased in PCa, and PSA screening has dramatically altered PCa presentation and management. Unfortunately, although high PSA levels are predictive of advanced PCa, a large fraction of organ-confined cancers present with much lower total PSA values that overlap those levels found in men without PCa. Measurement of free versus total PSA can increase specificity for PCa, and tests under development to measure forms of proPSA may further enhance the ability to detect early-stage PCa. PSA is also widely used to monitor responses to therapy and is under investigation as a therapeutic target. Finally, recent data indicate that there may be additional roles for PSA in the pathogenesis of PCa.

Prostate specific antigen doubling time as auxiliary end point in hormone refractory prostatic carcinoma

OBJECTIVE

In hormone refractory prostatic carcinoma (HRPCa), the majority of patients have bone metastases only, which are by definition non-measurable. This makes objective evaluation of chemotherapeutic agents difficult. Prostate specific antigen (PSA) as a dynamic model was analyzed as potential auxiliary end point in HRPCa.

METHODS

In the framework of a master protocol, the Swiss Group for Clinical Cancer Research (SAKK) is evaluating cytotoxic drugs in HRPCa since 1991. These prospective phase II trials include uniform requirements with regard to response, toxicity and quality of life. From the entire pool of patients, 40 with bidimensionally measurable metastases (lymph nodes, visceral organs) could be identified. PSA doubling time was calculated in patients with a rising PSA during therapy.

RESULTS

Objective best response to any given chemotherapeutic agent was: partial remission (PR) in six patients (15%), stable disease (SD) in 13 (32%) and progressive disease (PD) in 21 (53%). PSA remained stable or decreased in four of six patients with PR (67%), seven of 13 with SD (54%) but only in four of 21 with PD (19%) (Cochran-Armitage test for trend; p=0.015). The median PSA doubling time for patients with a rising PSA was 238 days in PR and 224 days in SD, compared to 113 days in PD (Wilcoxon test; p=0.002).

CONCLUSIONS

PSA doubling time is a potential auxiliary end point in the evaluation of cytotoxic drugs in HRPCa. Thus, also patients with non-measurable (bone) metastases could be included in analysis of response.

"PSA-itis": knowledge of serum prostate specific antigen and other causes of anxiety in men with metaststic prostate cancer

PURPOSE

High or increasing prostatic specific antigen (PSA) levels may be a source of anxiety in patients with metastatic prostate cancer.

MATERIALS AND METHODS

Patients with metastatic prostate cancer completed questionnaires, including the Prostate Cancer Specific Quality of Life Instrument, Hospital Anxiety and Depression Scale, and a questionnaire to assess the impact of the knowledge of PSA levels on anxiety. These were completed at home more than 3 days before or after a clinic appointment and returned by mail. Patient medical history was obtained from the record.

RESULTS

Of the 65 patients who consented to the study 52 returned the completed questionnaires. Median age was 70 years (range 55 to 86) and median time since diagnosis was 53 months. Of the patients 81% had hormone resistant disease. Most reported good overall quality of life with a median Prostate Cancer Specific Quality of Life Instrument score of 93 (maximum 100). Of the patients 77% indicated that PSA levels were one of the ways and 44% indicated they were the only way that they knew whether disease was progressing. When asked to rate preferences for treatment outcome, 25% of the men rated decreasing PSA and worse physical symptoms above increasing PSA and better physical symptoms. If measurement of PSA levels ceased, 52% of patients would believe that their doctor was giving up on them and only 1 would be relieved. Before receiving PSA results 76% reported some level of anxiety and 15% reported extreme anxiety.

CONCLUSIONS

PSA related anxiety represents a substantial problem in patients with metastatic prostate cancer.

Hormone-refractory Prostate Cancer

For more than five decades, the preferred treatment for advanced prostate cancer has been suppression of androgen production by medical or surgical castration. However, all patients treated with androgen deprivation eventually develop resistant disease as manifested by increasing prostate-specific antigen levels, progressive disease on imaging studies, and ultimately worsening symptoms. The treatment of patients with hormone-refractory prostate cancer (HRPC), once thought to represent a relatively futile endeavor, has changed significantly in the past several years with the development of new therapeutics. 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 heterogenous disease. Some patients may respond to alternative hormonal interventions despite the presence of castrate levels of testosterone. Furthermore, the application of chemotherapeutic regimens has provided viable treatment options for patients with HRPC.

Nomogram for overall survival of patients with progressive metastatic prostate cancer after castration

PURPOSE

To develop a pretreatment prognostic model for survival of patients with progressive metastatic prostate cancer after castration using parameters that are measured during routine clinical management.

PATIENTS AND METHODS

Pretreatment clinical and biochemical determinants from 409 patients enrolled onto 19 consecutive therapeutic protocols from June 1989 through January 2000 were evaluated. The factors selected were age, Karnofsky performance status (KPS), hemoglobin (HGB), prostate-specific antigen (PSA), lactate dehydrogenase (LDH), alkaline phosphatase (ALK), and albumin. These factors were combined in an accelerated failure time regression model to produce a nomogram to predict median, 1-year, and 2-year survival. The nomogram was validated internally and externally using data from a multicenter randomized trial of suramin plus hydrocortisone versus hydrocortisone alone.

RESULTS

The median survival of the entire group was 15.8 months (range, 0.9 to 77.8 months); 87% have died. In multivariable analysis, KPS, HGB, ALK, albumin, and LDH were significantly associated with survival (P <.05), whereas age and PSA were not. All seven factors were included in the nomogram. When applied to the external validation data set, the nomogram achieved a concordance index of 0.67. Calibration plots suggested that the nomogram was well calibrated for all predictions.

CONCLUSION

A nomogram derived from pretreatment parameters that are measured on a routine basis was constructed. It can be used to predict the median, 1-year, and 2-year survival of patients with progressive castrate metastatic disease with reasonable accuracy. The information is useful to assess prognosis, guide treatment selection, and design clinical trials.

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.

Plasma osteopontin: associations with survival and metastasis to bone in men with hormone-refractory prostate carcinoma

BACKGROUND

Osteopontin (OPN) is a secreted glycoprotein that is detectable in human body fluids. Its increased expression has been found in many malignancies, and a stimulatory effect on human prostate carcinoma cells in vitro has been demonstrated. Plasma OPN levels have been associated with tumor burden and survival in patients with metastatic breast carcinoma. The authors explored these associations in men with hormone-refractory prostate carcinoma (HRPC).

METHODS

Plasma samples from 100 men with HRPC were collected. OPN was measured using an antigen-capture enzyme-linked immunosorbent assay technique. Multivariable analyses were performed to identify predictors of OPN and survival.

RESULTS

At the time of OPN sampling, the median patient age was 73 years (range, 50-86 years), and 92% of patients had metastases. The median plasma OPN level was 198.5 ng/mL (range, 15.0-2363.0 ng/mL), the median prostate specific antigen level was 67.8 microg/L (range, 0.1-7550.0 microg/L), and the median survival was 13.7 months. OPN plasma levels were higher in patients with versus patients without bone metastases (P = 0.024). Multivariable modeling demonstrated an independent association of the OPN level with alkaline phosphatase, hemoglobin, and creatinine levels. The log-transformed OPN level (hazard ratio [HR], 2.38; P < 0.0001), performance status (HR, 2.43; P = 0.007), and a history of prior radiotherapy for localized prostate carcinoma (HR, 0.48; P = 0.0229) were independent predictors of survival in a Cox multivariate model.

CONCLUSIONS

In this study, in men with established HRPC, the plasma OPN level was associated with the presence of metastases to bone and with other measures of tumor burden, and it was correlated independently and negatively with survival.

Vinorelbine in androgen-independent metastatic prostatic carcinoma--a phase II study

The purpose of this study was to evaluate the efficacy of vinorelbine treatment in terms of prostate-specific antigen (PSA) response and clinical benefit (decrease of pain or analgesic score for the subgroup of patients with pain), as well as its toxicity in patients with progressive metastatic androgen-independent prostatic carcinoma. 44 patients with prostatic carcinoma progressing after orchiectomy or during treatment with hormonal agents were treated with vinorelbine at a dose of 30 mg/m(2) intravenously (i.v.) on days 1 and 8 of a 21-day cycle. Inclusion criteria were metastatic progressive prostatic carcinoma with prostate-specific antigen (PSA) serum levels >/=3 x upper limit of normal, World Health Organization (WHO) performance status </=2, age <85 years and adequate bone marrow, liver and renal functions. Treatment was continued until progression or a maximum of 12 cycles. Treatment was delayed for a week if haematological toxicity grade >/=2 was observed on the day of scheduled vinorelbine administration. 9 patients received less than three cycles, 6 due to rapid tumour progression. Treatment at day 1 had to be delayed in 13.7% of 183 cycles. Treatment at day 8 had to be omitted in 19.7% of all cycles. Grade >/=3 granulocytopenia occurred in 18% of patients. 4 patients had severe constipation. In 7 patients (15.9%, Confidence Interval (CI) 6.6-30.1%), a PSA response (>/=50% reduction of PSA levels) was observed. Among 8 patients with measurable disease, 3 had partial remission and 1 no change. Median time to PSA progression in 43 assessable patients was 11.9 weeks (range 3-52 weeks). Median duration of PSA response was 14 weeks (9-30 weeks). Clinical benefit was seen in 7 of 31 cases (23%) with baseline pain, there was no association with PSA response. Vinorelbine is a fairly well tolerated drug with a moderate single agent activity in patients with androgen-refractory prostate cancer.

Assessing outcomes in palliative chemotherapy

Patients with metastatic cancer are often offered systemic chemotherapy, although it is not usually curative in this situation. The impact of treatment on survival may be small and the intention is mainly to palliate symptoms and to improve the patient's quality of life. Traditional end points in clinical trials tend to focus on cancer outcomes, such as tumour shrinkage or survival. Trials of palliative chemotherapy should focus on patient outcomes that reflect the aims of treatment. There are now a large number of instruments available to measure quality of life and the difficulty lies in deciding which tools are appropriate and applying them consistently to give results that are robust enough to enable clinical decision making. This is particularly challenging in a population of patients with a high degree of morbidity. In addition, economic end points are becoming increasingly relevant in the current climate: as newer treatments become available, the ways in which costs may be balanced against the potential benefits in terms of gains in quality of life become important.

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.

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.

The treatment challenge of hormone-refractory prostate cancer

BACKGROUND

Both the demographics and treatment of hormone-refractory prostate cancer (HRPC) are changing. Patients are younger and healthier, with fewer comorbidities. The "no treatment until symptoms" approach is disappearing. Chemotherapy is increasingly being utilized.

METHODS

The authors review the steps involved in hormone management before chemotherapy is considered. The roles for chemotherapy in current clinical trials are examined.

RESULTS

Effective hormonal management of the prostate cancer patient incorporates an understanding of the stages of hormone sensitivity and prescribing additional interventions beyond simple castration. Once hormone refractoriness is established, the combination of mitoxantrone and prednisone has become a standard chemotherapeutic approach. New agents such as docetaxel are being tested in phase III trials against mitoxantrone plus prednisone.

CONCLUSIONS

HRPC is now regarded as a chemotherapy-sensitive tumor. The goals of chemotherapy in HRPC are to decrease PSA level and improve quality of life. New agents and combinations are needed to improve survival.

Fixed higher dose schedule of suramin plus hydrocortisone in patients with hormone refractory prostate carcinoma a multicenter Phase II study

BACKGROUND

Using a fixed higher-dose schedule, the efficacy and toxicity of suramin plus hydrocortisone were assessed in patients with metastatic hormone-refractory prostate carcinoma (HRPC).

METHODS

Fifty consecutive patients with HRPC (including those in whom hormonotherapy was withdrawn) and an Eastern Cooperative Oncology Group performance status of 0-2 were recruited. Treatment was comprised of a bolus intravenous infusion of 200 mg of suramin followed by suramin (500 mg/m(2) intravenously [i.v.] over 24 hours) given daily over 5 days as a loading course, followed by suramin (350 mg/m(2) i.v. over 2 hours) administered weekly for 12 weeks. This 12-week course was repeated at 6-month intervals. All patients received concomitant hydrocortisone.

RESULTS

Five hundred fifty weekly doses of therapy were delivered over the course of the entire study. A partial response, based on a > 50% decrease in the prostate specific antigen (PSA) level, was achieved in 27 patients (54%; 95% confidence interval [95% CI], 44.7-65.0%), 16 of whom (32%; 95%CI, 23.9-43.2%) had a > 75% decrease in their PSA levels. The measurable disease objective response rate was 18% (95% CI, 2.3-51.8%). Of the 37 patients with bone pain requiring analgesia, 27 patients (73%; 95% CI, 55.9-86.2%) reduced their medication consumption to a lower level on the World Health Organization analgesic ladder. The median duration of response was 15.5 weeks (range, 6-70 weeks), the median time to disease progression was 13 weeks, and the median overall survival time was 11 months. Treatment generally was well tolerated. Fatigue and severe lymphopenia were the most commonly reported significant toxicities. In addition, there was 1 septic toxic death reported, and 10% of the patients were found to have NCI Grade 3-4 neurotoxicity.

CONCLUSIONS

The results of the current study demonstrated that the fixed-dose suramin regimen administered herein showed high, although short-lived, activity and a good tolerance profile in HRPC patients.

A phase II study of the bispecific antibody MDX-H210 (anti-HER2 x CD64) with GM-CSF in HER2+ advanced prostate cancer

The proto-oncogene HER2 presents a novel therapeutic target. We report results in 25 patients with HER2+ advanced prostate cancer treated with the bispecific antibody MDX-H210 15 microg m(-2)by intravenous infusion plus GM-CSF 5 microg kg(-1)day(-1)by subcutaneous injection for 4 days repeated weekly for 6 weeks. Patients with stable disease or better received further cycles of treatment until disease progression or study withdrawal. 1 patient received no treatment and 4 received less than 1 cycle and are included in the toxicity analysis only. Median duration of follow up was 105+ (range 21-188) days. Toxicity was generally NCI-CTG 0-2. There were 2 grade 4 adverse events (heart failure and dyspnoea) and 1 grade 3 event (allergic reaction) resulting in discontinuation of the study medication. There were 9 further grade 3 events not resulting in trial withdrawal. There were no treatment-related deaths. 7/20 (35%) evaluable patients had a >50% PSA response of median duration 128 (range 71-184+) days. 7/12 (58%) patients with evaluable pain had improvements in pain scores. The PSA relative velocity on therapy decreased in 15/18 (83%) assessable patients compared to pre-study. GM-CSF and MDX-H210 is active in hormone refractory prostate carcinoma with acceptable toxicity; further studies are warranted.

A retrospective analysis of the relationship between changes in serum PSA, palliative response and survival following systemic treatment in a Canadian randomized trial for symptomatic hormone-refractory prostate cancer

BACKGROUND

To investigate the relationship between changes in serum PSA, palliative response and survival following systemic treatment for symptomatic hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

A retrospective review of 161 patients, treated with mitoxantrone and prednisone (M + P) (n = 80), or prednisone alone (P) (n = 81) from a Canadian randomized phase III clinical trial. PSA response was defined by > or =50% decline compared to baseline. Palliative response was defined by the primary and secondary endpoints of the trial. All responses were required to be maintained on two visits at least three weeks apart. The Cox proportional hazards model and a landmark analysis (at nine weeks) were used to evaluate survival differences between PSA responders and non-responders.

RESULTS

Using an intent-to-treat analysis in which patients with missing PSA data are considered non-responders, 34% of M + P and 11% of P patients achieved a PSA response (P = 0.0001). Nineteen of thirty-six (53%) patients with PSA response and twenty-six of ninety (29%) patients without PSA response achieved a palliative response (P = 0.001 Chi-square test, phi coefficient = 0.28). From the landmark analysis. PSA responders had longer survival than non-responders (P = 0.009). In multivariate analysis, better performance status, higher hemoglobin and PSA response (P < 0.001) predicted for survival, but palliative response did not (P = 0.11).

CONCLUSIONS

There is significant but imperfect statistical association between PSA response and palliative response. PSA response was associated with longer survival. Patients treated with M + P were more likely to achieve a PSA response and a palliative response than those treated with P.

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

PURPOSE

Validated end points are lacking for clinical trials in hormone-refractory prostate cancer (HRPC). Controversy remains regarding the utility of a posttreatment decline of prostate-specific antigen (PSA). The purpose of this study was to determine whether posttreatment declines in PSA were associated with clinical measures of improvement in a randomized phase III trial of suramin plus hydrocortisone versus placebo plus hydrocortisone.

PATIENTS AND METHODS

A total of 460 HRPC patients were randomized to receive suramin plus hydrocortisone (n = 229) or placebo plus hydrocortisone (n = 231). All patients had symptomatic, metastatic HRPC requiring opioid analgesics. Clinical end points evaluated included overall survival, objective progression-free survival (OPFS), and time to pain progression (TTPP). An evaluation of overall survival, OPFS, and TTPP as a function of a PSA decline of > or = 50%, lasting at least 28 days, was undertaken by using a landmark analysis at 6, 9, and 12 weeks. A multivariate analysis of the impact of PSA decline was performed on these clinical end points.

RESULTS

A decline in PSA of > or = 50% lasting > or = 28 days was significantly associated with a prolonged median overall survival, OPFS, and TTPP, both in the entire group and the suramin plus hydrocortisone group at all three landmarks in both univariate and multivariate analysis.

CONCLUSION

In this prospective, randomized trial of suramin plus hydrocortisone versus placebo plus hydrocortisone, a posttherapy decline in PSA of > or = 50%, lasting 28 days, was associated with prolonged median overall survival, improved median progression-free survival, and median TTPP. This analysis suggests that a posttreatment decline in PSA may be a reasonable intermediate end point in HRPC trials and calls into question the clinical utility of preclinical assays evaluating the in vitro effect of given agents on PSA secretion.

Low doses of oral dexamethasone for hormone-refractory prostate carcinoma

BACKGROUND

Although glucocorticoids have been used to treat patients with hormone-refractory prostate carcinoma (HRPC), reports have varied regarding the types and doses of glucocorticoids used as well as their clinical benefits. In the current study, low doses of dexamethasone were investigated for their specific beneficial effects and the feasibility of long term treatment.

METHODS

Thirty-seven patients diagnosed with HRPC were treated with oral dexamethasone (0.5-2 mg/day). The patients ranged in age from 53-89 years (median, 74 years). Thirty-two patients, including 6 with lymph node metastases, had bone involvement whereas only 5 patients were found to have elevated serum prostate specific antigen (PSA) levels.

RESULTS

Twenty-three patients (62%) who received no other concomitant therapy demonstrated a decline in their serum PSA level of > or = 50%, which was confirmed by a second PSA value obtained > or = 4 weeks later. The median time to PSA progression was 9 months. Among 18 patients with bone pain, 11 (61%) had improvement and in 5 patients (28%) the pain became stable. Among 21 patients with interpretable bone scans, 4 (19%) showed improvement and 8 (38%) achieved stable disease. Both symptomatic and objective responses of bone metastases were correlated with declines in the serum PSA level of > or = 50%. Ten patients achieved an increase in their hemoglobin level of at least 2 g/dL. Patients whose PSA level declined by > or = 50% with therapy had significantly prolonged survival (median, 22 months). As pretreatment markers, a longer interval before the initial evidence of disease progression appeared was found to correlate significantly with posttherapy PSA declines of > or = 75%. All side effects of the glucocorticoids were reported to be mild.

CONCLUSIONS

Low doses of dexamethasone were found to be beneficial in the treatment of HRPC, decreasing the severity of anemia and osseous disease as well as reducing serum PSA levels. A posttherapy serum PSA decline of > or = 50% appears to be a reliable marker of improved survival with this therapy.

Chemotherapy in advanced androgen-independent prostate cancer 1990-1999: a decade of progress?

BACKGROUND AND PURPOSE

A great number of clinical research studies have been reported in the field of chemotherapy for advanced androgen-independent prostate cancer during the last ten years. The aims of the present review were to assess their impact on management of the disease and on survival of patients.

METHODS

The review of full published reports was facilited by the use of a MEDLINE computer search.

RESULTS

Clinical research studies have focused on defining guidelines for eligibility criteria and accurate endpoints for patients to be enrolled onto clinical trials and developing new agents or combination of drugs including estramustine phosphate. Any combination of current chemotherapy has no impact on overall survival of patients. Among drugs in development, only the promising activity observed with docetaxel deserves randomized trials to assess its impact on survival. The major innovative advance of the 90s is the demonstration of the impact of chemotherapy (mitoxantrone + prednisone) on quality of life as compared to prednisone alone. A greater and longer-lasting improvement in quality of life along with a concomitant decrease in costs was observed.

CONCLUSIONS

At the present time, chemotherapy should be considered as a palliative treatment in patients with symptomatic androgen-independent disease. The enrollment of patients into clinical trials dealing with quality of life as primary endpoint is strongly solicited. A standard methodology should be used in phase II trials with a primary goal of selection of agents which should progress to randomized trials using survival as an endpoint. Hopefully new specific strategies targeted to reverse the molecular changes that underlie prostate tumorigenesis should rapidly impact the multimodality management of AIPC in the third millenium.

Recent advances in chemotherapy for advanced prostate cancer

Recently, several important studies have validated prostate-specific antigen (PSA) as a reliable measure of response to chemotherapeutic treatment in advanced hormone-refractory prostate cancer. Furthermore, although chemotherapy in this setting has always been considered palliative, several analyses of recent clinical trials have demonstrated a significant association between declines in PSA values of 50% or more and prolonged survival. Mitoxantrone, in combination with prednisone, has been shown to provide significant palliation and improved quality of life. The use of combinations of chemotheraputic agents also seems to provide significantly superior objective and subjective responses compared with single-agent regimens. In particular, estramustine has been shown to synergize many of the agents used in prostate cancer treatment and has been demonstrated to provide significant palliation and decline in PSA levels in combination with vinblastine, vinorelbine, etoposide, paclitaxel, and docetaxel. The results of several important trials of the taxanes both as single agents and in combination with estramustine have been completed in the past year and have demonstrated that these agents are very effective in the treatment of hormone-refractory prostate cancer.

Suramin therapy for patients with symptomatic hormone-refractory prostate cancer: results of a randomized phase III trial comparing suramin plus hydrocortisone to placebo plus hydrocortisone

PURPOSE

Suramin is a novel agent that has demonstrated preliminary evidence of antitumor activity in hormone-refractory prostate cancer (HRPC). A prospective randomized clinical trial was designed to evaluate pain and opioid analgesic intake as surrogates for antitumor response in HRPC patients with significant, opioid analgesic-dependent pain.

PATIENTS AND METHODS

A double-blind, placebo-controlled trial randomized patients to receive a 78-day, outpatient regimen of either suramin plus hydrocortisone (HC, 40 mg/d) or placebo plus HC. Treatment assignment was unblinded when either disease progression or dose-limiting toxicity occurred; placebo patients were allowed to cross-over to open-label suramin plus HC. In addition to pain and opioid analgesic intake, prostate-specific antigen (PSA) response, time to disease progression, quality of life, performance status, and survival were compared.

RESULTS

Overall mean reductions in combined pain and opioid analgesic intake were greater for suramin plus HC (rank sum P =.0001). Pain response was achieved in a higher proportion of patients receiving suramin than placebo (43% v 28%; P =.001), and duration of response was longer for suramin responders (median, 240 v 69 days; P =.0027). Time to disease progression was longer (relative risk = 1.5; 95% confidence interval, 1.2 to 1.9) and the proportion of patients with a greater than 50% decline in PSA was higher (33% v 16%; P =.01) in patients who received suramin. Neither quality of life nor performance status was decreased by suramin treatment, and overall survival was similar. Most adverse events were of mild or moderate intensity and were easily managed medically.

CONCLUSION

Outpatient treatment with suramin plus HC is well tolerated and provides moderate palliative benefit and delay in disease progression for patients with symptomatic HRPC.

Doxil (Caelyx): an exploratory study with pharmacokinetics in patients with hormone-refractory prostate cancer

Doxil, a doxorubicin formulation of polyethylene glycol-coated liposomes, has anti-tumor activity against Kaposi's sarcoma and other solid tumors with mild myelosuppression, minimal hair loss and a low risk of cardiotoxicity. Non-liposomal doxorubicin has modest activity in hormone-refractory prostate cancer (HRPC) with considerable toxicity. A pilot study of Doxil was conducted in 15 patients with HRPC. Doxil was administered i.v. using two regimes of equal dose intensity, either 45 mg/m2 every 3 weeks or 60 mg/m2 every 4 weeks. Plasma levels of doxorubicin were analyzed in 10 patients. The most common side effect was stomatitis with a higher incidence at the 60 mg/m2 dose level. In contrast, hand-foot syndrome was more frequent and severe in patients treated with the 3 week schedule of 45 mg/m2. Three patients responded to treatment (based on objective response in one patient and reduction of PSA level greater than 50% in the other two) and two patients had stable disease, all of them receiving 60 mg/m2. Pharmacokinetic analysis shows a proportional increase of plasma drug levels with dose and the characteristic long circulation time of Doxil with half-lives in the range of 3 days, somewhat longer than previously reported. In conclusion, Doxil at 60 mg/m2 every 4 weeks appears to be active against HRPC, but severe mucocutaneous toxicities prevented further investigation of this regime.

New treatment strategies in advanced prostate cancer

The treatment of advanced prostate cancer has evolved rapidly in the last 5 years. Therapeutic options for patients with advanced disease, once essentially limited to the use of androgen deprivation, have expanded to include a number of interventions, including secondary hormonal manipulations, chemotherapy, and a variety of investigational approaches. Novel therapeutic approaches in prostate cancer patients are likely to be undertaken in patients with disease that is at or below the limits of detection by current imaging technology, so novel methods will be essential to the successful evaluation and use of these agents.

Etoposide in prostate cancer

Hormone refractory prostate cancer is a disease that kills approximately 39,000 people per year. No single chemotherapeutic agent or regimen has been demonstrated to provide a survival advantage in this disease. Etoposide as a single agent, both in i.v. and oral formulations has not proven to be effective. In the 1990s, however, etoposide has been combined with several agents to create novel treatment regiments for patients with hormone refractory disease. Several of these regimens, all involving oral etoposide, have demonstrated promising results in Phase II trials and early results suggest that they may increase survival for hormone refractory patients, although this remains to be tested in a Phase III trial setting.

Anti-androgens and other hormonal therapies for prostate cancer

Many men who show evidence of a progression of prostate cancer by rising prostate-specific antigen (PSA) or other symptoms are treated with anti-androgens. Anti-androgen withdrawal represents the first line of treatment after failure of hormonal manipulation. Flutamide is an approved anti-androgen that has been incorporated in many of the combined androgen blockade studies. Bicalutamide is also a nonsteroidal anti-androgen that offers the advantages of reduced dosage amounts and reduction in side effects. Additionally, there are a variety of therapeutic agents that can suppress adrenal secretion of androgens. The most promising of these agents include aminoglutethamide, ketoconazole, and corticosteroids, with an expected response rate of 10% to 15%. Studies have shown that some patients may respond to an anti-estrogen such as tamoxifen. There are a variety of therapeutic treatment options available for patients with hormone refractory prostate cancer. However, quality-of-life issues are becoming increasingly important and should be incorporated into clinical trial endpoints.

Chemotherapy for advanced hormone refractory prostate cancer

Men with metastatic prostate cancer treated with androgen ablation respond rapidly and often dramatically to therapy, with improvement of bone pain, regression of soft tissue metastases, and declines in serum prostate-specific antigen (PSA). Unfortunately, few treatment options are available to men who progress after hormone therapy. Recent studies in the mechanism of anticancer drug action have focused on the proteins that regulate apoptosis or programmed cell death as a target for the treatment of hormone-resistant prostate cancer. New treatments are now being designed with both resistance and apoptotic pathways in mind. US Food and Drug Administration (FDA) approval of the combination of mitoxantrone and prednisone for the palliation of bone pain in men with hormone refractory prostate cancer demonstrates that chemotherapy can be effective. Two randomized trials have demonstrated the superiority of mitoxantrone combined with a corticosteroid over corticosteroid therapy in alleviating bone pain. The combination of estramustine with vinblastine, or VP-16, is commonly used in clinical practice with both regimens demonstrating significant PSA declines. When estramustine is combined with either paclitaxel or docetaxel in vitro, greater than additive in vitro cytotoxicity is noted. Phase I and II studies of taxane-based therapy in hormone refractory prostate cancer demonstrate improved survival when compared with historical controls, but phase III studies are necessary to confirm these preliminary observations.

Eligibility and response guidelines for phase II clinical trials in androgen-independent prostate cancer: recommendations from the Prostate-Specific Antigen Working Group

PURPOSE

Prostate-specific antigen (PSA) is a glycoprotein that is found almost exclusively in normal and neoplastic prostate cells. For patients with metastatic disease, changes in PSA will often antedate changes in bone scan. Furthermore, many but not all investigators have observed an association between a decline in PSA levels of 50% or greater and survival. Since the majority of phase II clinical trials for patients with androgen-independent prostate cancer (AIPC) have used PSA as a marker, we believed it was important for investigators to agree on definitions and values for a minimum set of parameters for eligibility and PSA declines and to develop a common approach to outcome analysis and reporting. We held a consensus conference with 26 leading investigators in the field of AIPC to define these parameters.

RESULT

We defined four patient groups: (1) progressive measurable disease, (2) progressive bone metastasis, (3) stable metastases and a rising PSA, and (4) rising PSA and no other evidence of metastatic disease. The purpose of determining the number of patients whose PSA level drops in a phase II trial of AIPC is to guide the selection of agents for further testing and phase III trials. We propose that investigators report at a minimum a PSA decline of at least 50% and this must be confirmed by a second PSA value 4 or more weeks later. Patients may not demonstrate clinical or radiographic evidence of disease progression during this time period. Some investigators may want to report additional measures of PSA changes (ie, 75% decline, 90% decline). Response duration and the time to PSA progression may also be important clinical end point.

CONCLUSION

Through this consensus conference, we believe we have developed practical guidelines for using PSA as a measurement of outcome. Furthermore, the use of common standards is important as we determine which agents should progress to randomized trials which will use survival as an end point.

Suramin in combination with weekly epirubicin for patients with advanced hormone-refractory prostate carcinoma

BACKGROUND

Suramin and epirubicin are both active agents in the treatment of patients with hormone-refractory advanced prostate carcinoma, with demonstrated antitumor synergism in vitro on human prostate carcinoma cells and different dose-limiting toxicities. The authors conducted this Phase II study to determine the feasibility, toxicity, and antitumor activity of suramin in combination with epirubicin.

METHODS

Only patients with hormone-independent advanced prostate carcinoma who had progressive disease after the last therapeutic maneuver they had undergone, including antiandrogen withdrawal, entered the study. Suramin was administered initially as a 6-day continuous infusion for 10 consecutive weeks and then for 6 days every 28 days for a maximum of 6 months. Doses were determined by a computer-assisted dosing system that used Bayesian pharmacokinetics to maintain suramin plasma concentrations of 200-250 microg/mL. Cortisone acetate 25 mg, administered at 8 a.m. and 8 p.m. daily, was begun 4 weeks after the initiation of suramin therapy. Epirubicin 25 mg/m2 was given as a weekly intravenous bolus beginning on Day 1 and was continued for a maximum of 6 months.

RESULTS

Twenty-six patients entered the study. Toxicities mainly included World Health Organization Grade 1-2 nausea, fatigue, anorexia, neutropenia, peripheral neuropathy, creatinine elevation, proteinuria, and prolonged prothrombin time, whereas Grade 3 toxicities were uncommon. Among 11 patients with measurable disease, 3 (27%) demonstrated an objective response. Among 24 patients evaluated for prostate specific antigen (PSA) response, 8 (33%; 95% confidence interval 16-55%) had a > or =50% decrease in PSA levels, which lasted a median of 32 (range, 8-52) weeks. Median progression free and overall survival were both 8 months.

CONCLUSIONS

The combination of suramin and epirubicin used in the current study is feasible, is associated with moderate toxicities, and has antitumor activity in advanced hormone-refractory prostate carcinoma. However, the results obtained with this combination do not represent major improvements in the treatment of patients with this disease, compared with suramin or epirubicin alone or other available treatments.

Hydrocortisone with or without mitoxantrone in men with hormone-refractory prostate cancer: results of the cancer and leukemia group B 9182 study

PURPOSE

Approximately 40,000 men die each year of hormone-refractory prostate cancer (HRPC). The results of treatment with chemotherapy have been disappointing to date, with no trials demonstrating a benefit with respect to survival duration. Corticosteroids and mitoxantrone each have been shown to be active agents in this disease. The purpose of this study was to demonstrate an advantage of mitoxantrone and hydrocortisone (M+H) over hydrocortisone alone with respect to survival duration.

PATIENTS AND METHODS

Two hundred forty-two patients with HRPC were randomized to receive either M+H or hydrocortisone alone. Patients were monitored for survival, time to disease progression, time to treatment failure, response, and quality-of-life (QOL) parameters.

RESULTS

Treatment in both arms was well tolerated. Although there was a delay in time to treatment failure and disease progression in favor of M+H over hydrocortisone alone, there was no difference in overall survival (12.3 months for M+H v 12.6 months for hydrocortisone alone). There was an indication that QOL was better with M+H, in particular with respect to pain control.

CONCLUSION

M+H generated more frequent responses and a delay in both time to treatment failure and disease progression compared with hydrocortisone alone. In addition, there was a possible benefit of M+H with respect to pain control over hydrocortisone alone. No improvement in survival was observed. Although M+H could be viewed as a palliative option for patients with HRPC, new drugs and novel strategies are needed to improve survival for this disease.

A phase II trial of irinotecan in hormone-refractory prostate cancer

Irinotecan is a DNA topoisomerase I inhibitor that has a wide spectrum of activity against human tumors in both preclinical and clinical studies. To evaluate the efficacy of irinotecan in hormone-refractory prostate cancer, we conducted a phase II study in 15 men with metastatic, PSA-progressive disease after primary androgen deprivation. Irinotecan was administered at a dose of 125 mg/m2 weekly for four weeks followed by a two-week rest period; cycles were repeated every six weeks. Response was assessed by evaluation of serial changes in the serum PSA. None of fifteen patients had a decline in PSA of greater than 50%; eight patients had stable disease as a best response. None of three patients with measurable disease had a partial or complete response. Toxicity was primarily hematologic and gastrointestinal, with 40% of patients requiring dose modification due to granulocytopenia and 20% requiring intravenous fluid supplementation after development of diarrhea. There were no treatment-related deaths. We conclude that irinotecan in the dose and schedule used in this trial does not have significant activity against hormone-refractory prostate cancer.

Serologic tumor markers, clinical biology, and therapy of prostatic carcinoma

PSA has been a valuable tool in enhancing our understanding of the prevalence and virulence of prostate cancer. PSA also has contributed to the understanding of important phenomena related to the androgen regulation of the cancer; however, it has not been useful in detecting some forms of androgen-independent (neuroendocrine) progression and is of limited prognostic value in androgen-independent prostate cancer. PSA also has been valuable in the accelerated development of therapies for prostate cancer; however, it must be used cautiously for this purpose, because it may not reflect the most relevant clone. In addition, some agents may directly affect PSA release independent of their antitumor activity. Most importantly, before PSA is adopted as a surrogate end point in clinical trials in prostate cancer, it must be prospectively validated. Future studies must focus on the development of prospective serologic tumor markers that can predict virulence of disease and to reflect androgen-independent progression.

Oral chemotherapy for hormone refractory prostate cancer. The University of Michigan experience

The use of oral chemotherapy for the treatment of malignant disease is expanding. The authors' experience with oral chemotherapy for hormone-refractory prostate cancer continues to grow. These therapies are well-tolerated and effective. Already, these regimens are being improved by hybridizing them with intravenous agents such as paclitaxel. Also, oral novel agents are being tested that may offer new options for the treatment of hormone-refractory prostate cancer.

Advances in prostate cancer

The causes of prostate cancer reflect a complex interaction between environmental and genetic factors. Improvement in screening has reduced the incidence of prostate cancer, and risk assessment schemata have enhanced therapy, both for localized disease and for locally recurrent prostate cancer. The use of hormone therapy has been further evaluated, as primary therapy for locally advanced cancers, for lymph node-positive cancers, and for de novo metastatic cancer. Modest inroads have been made in the treatment and understanding of androgen-independent prostate cancer. Advances have been made in the understanding of the risk factors, genetic and environmental, associated with the development and progression of prostate cancer; in screening; and in optimizing therapy for localized, locally recurrent, and advanced disease. This article reviews the most salient observations reported between November 1, 1997 and October 31, 1998.

Prognostic indicators in hormone refractory prostate cancer

Prognostic factors in hormone refractory prostate cancer currently are of limited use to clinicians. Although studies have identified several factors that predict for poor survival in patients, most are either retrospective, or nonrandomized. Therefore, large prospective, randomized trials are needed to validate the significance of these factors. In addition, these indicators are largely descriptive of the patients' condition or the extent of disease. As more treatment options are developed for these patients, functionally relevant and prognostic molecular markers are needed to direct their care.

Prostate-specific antigen and other markers of therapeutic response

Several new agents and combinations demonstrate significant activity in the treatment of patients with hormone refractory prostate cancer. Prostate-specific antigen (PSA) is being used increasingly as the key marker of a therapeutic response in trials of new agents. This article reviews data that support this marker as a surrogate endpoint, and it discusses the issues around the appropriateness of PSA as an intermediate marker with evolving noncytotoxic agents. Other biomarkers of prostate cancer progression are not uniformly elevated in men with advanced disease; to date, they are of limited clinical use. This article also discusses the rationale and results of novel and alternative biomarkers of prostate cancer progression.

Secondary hormonal manipulations in hormone refractory prostate cancer

Hormone refractory prostate cancer is clinically heterogeneous, and many patients retain sensitivity to subsequent hormonal manipulations, even after combined androgen blockage. Antiandrogen withdrawal is a mandatory first step. Subsequent treatment with an alternate antiandrogen, adrenal androgen inhibitor (such as ketoconazole), or glucocorticoid may provide both subjective and objective clinical benefit in up to 65% of patients.

Post-therapy serum prostate-specific antigen level and survival in patients with androgen-independent prostate cancer

BACKGROUND

With an hypothesis that post-chemotherapy changes in serum prostate-specific antigen (PSA) levels might serve as a surrogate marker for assessing prostate cancer outcome (i.e., survival), we studied the relationship between pretherapy and post-therapy prognostic factors and survival in patients with androgen-independent prostate cancer.

METHODS

A prognostic model for survival based on pretherapy and post-therapy parameters was developed from the clinical data on 254 patients with androgen-independent prostate cancer treated with 11 different protocol therapies at Memorial Sloan-Kettering Cancer Center. The model was validated by use of an independent dataset of 541 patients enrolled in two randomized phase III trials.

RESULTS

In multivariate analysis, a post-therapy decline in PSA levels of 50% achieved in 12 weeks was a statistically significant factor associated with survival (two-sided P = .0012). A similar outcome was obtained with the use of an 8-week time frame. Elevated pretherapy level of serum lactate dehydrogenase (two-sided P = .0001), lower pretherapy level of hemoglobin (P = .0001), and younger age (two-sided P = .0430) had a statistically significant negative impact on outcome. Median survival times were 23, 17, and 9 months for low-, intermediate-, and high-risk groups of patients defined by the prognostic model, respectively.

CONCLUSION

This study confirms the prognostic value of a post-therapy decline in PSA of 50% or greater from baseline in relation to survival in patients with androgen-independent prostate cancer treated with a variety of therapies. Two consecutive determinations at 4-week intervals can be used as an end point for efficacy in phase II trials of therapies in this disease.