Phase II study of platinum and mitoxantrone in metastatic prostate cancer: a Southwest Oncology Group Study

Anti-tumour activity of platinum compounds in advanced prostate cancer-a systematic literature review

BACKGROUND

For men with advanced castration-resistant prostate cancer (CRPC), several treatment options are available, including androgen receptor (AR) pathway inhibitors (abiraterone acetate, enzalutamide), taxanes (docetaxel, cabazitaxel) and the radionuclide (radium-223). However, cross-resistance is a clinically relevant problem. Platinum compounds have been tested in a number of clinical trials in molecularly unselected prostate cancer patients. Advances in CRPC molecular profiling have shown that a significant proportion of patients harbour DNA repair defects, which may serve as predictive markers for sensitivity to platinum agents.

OBJECTIVE

To systematically identify and analyse clinical trials that have evaluated platinum agents in advanced prostate cancer patients.

METHODS

PubMed was searched to identify published clinical trials of platinum agents in advanced prostate cancer. The PRIMSA statement was followed for the systematic review process. Identified trials are analysed for study design, statistical plan, assessments of anti-tumour activity and the potential value of predictive biomarkers.

RESULTS

A total of 163 references were identified by the literature search and 72 publications that met the selection criteria were included in this review; of these 33 used carboplatin, 27 cisplatin, 6 satraplatin, 4 oxaliplatin and 2 other platinum compounds. Overall, anti-tumour activity varies in the range of 10%-40% for objective response and 20%-70% for PSA decline ≥50%. Response seemed highest for the combinations of carboplatin with taxanes or oxaliplatin with gemcitabine. The interpretation of the clinical data is limited by differences in response criteria used and patient populations studied.

CONCLUSION

Platinum compounds have moderate anti-tumour activity in molecularly unselected patients with advanced prostate cancer. Translational evidence of DNA repair deficiency should be leveraged in future studies to select prostate cancer patients most likely to benefit from platinum-based therapy.

Is there a role for platinum chemotherapy in the treatment of patients with hormone-refractory prostate cancer?

Docetaxel chemotherapy is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC). Platinum chemotherapy drugs, such as cisplatin and carboplatin, have moderate single-agent activity in HRPC. Next-generation platinum drugs, including satraplatin and oxaliplatin, may have additional activity in the management of HRPC. Furthermore, neuroendocrine differentiation may play a role in disease progression, providing a rationale for platinum-based chemotherapy in the management of HRPC. The authors reviewed the MEDLINE database for reports related to platinum-based chemotherapy in patients with advanced prostate cancer and evaluated studies that reviewed the role of neuroendocrine differentiation in the progression of HRPC. Older studies from the 1970s and 1980s suggested a lack of activity of cisplatin and carboplatin; however, those studies were flawed at least in part by their methods of response assessment. More recent Phase II studies of carboplatin suggested a moderate level of clinical and palliative activity when it was used as a single agent. However, when carboplatin was combined with a taxane and estramustine, high response rates were observed in several recent clinical trials. In addition, a randomized trial suggested that satraplatin plus prednisone improved progression-free survival compared with prednisone alone. For patients who progressed after docetaxel, no standard options existed in the literature that was reviewed. Several preliminary reports suggested that carboplatin and oxaliplatin may have activity as second-line chemotherapy. Platinum chemotherapy drugs historically have been considered inactive in HRPC, although a review of the data suggested otherwise. Carboplatin, in particular, induced very high response rates when it was combined with estramustine and a taxane, but it also appeared to have activity in patients who progressed after docetaxel. Satraplatin plus prednisone is being investigated in a large Phase III trial as second-line chemotherapy for HRPC. Targeting neuroendocrine cells may provide a new therapeutic approach to HRPC.

Satraplatin: an orally available platinum analog for the treatment of cancer

Satraplatin is a novel, orally bioavailable, platinum anticancer drug. Platinum analogs form the mainstay of treatment for a number of cancers, including lung, ovarian, colorectal and head and neck cancer. A disadvantage of the currently marketed platinum analogs is that they must all be administered via intravenous infusion. In addition, their utility is often limited by toxicity, particularly neurotoxicity, ototoxicity and renal toxicity. Satraplatin has preclinical antitumor activity comparable with that of cisplatin and, clinically, has a more manageable side-effect profile. Satraplatin is active in lung, ovarian and prostate cancer, and appears to have good efficacy in combination with radiation for lung and head and neck cancer. Preclinical data suggest it may also be effective for the treatment of certain cisplatin-refractory tumors. A large, randomized Phase III trial is currently evaluating satraplatin in combination with prednisone for the treatment of patients with hormone-refractory prostate cancer whose disease has progressed following prior systemic therapy. Positive results from this trial would support regulatory approval for satraplatin for this indication. The availability of an active oral platinum agent, such as satraplatin, with few of the serious toxicities associated with traditional intravenous platinum compounds makes satraplatin an alternative to other platinum agents and a new treatment option in the oncologist's armamentarium.

Therapieoptionen beim hormonrefraktären Prostatakarzinom

For a long time, hormone-refractory prostate cancer was regarded as a chemoresistant tumor. The introduction of taxanes has prompted a change in this opinion. For the first time treatment with 75 mg/m(2) docetaxel every 3 weeks has evidenced a survival benefit in a phase III trial (median survival of 18.9 months versus 16.5 months with mitoxantrone). Further advantages were improved pain reduction and quality of life. Neutropenia was foremost among the side effects. Docetaxel is currently the standard treatment for hormone-refractory prostate cancer. The morbidity of metastatic hormone-refractory prostate cancer is influenced by bone metastases. Pain is a prominent feature. Skeletal complications are frequent. Therapy with 4 mg zoledronic acid reduced skeletal complications significantly in comparison to placebo. The most pronounced effect is the reduction of pathological fractures. Side effects include flu-like symptoms, muscle pain, and edemas. Zoledronic acid also belongs to the standard treatment of hormone-refractory prostate cancer with bone metastases.

A phase I and pharmacokinetic study of irofulven and cisplatin administered in a 30-min infusion every two weeks to patients with advanced solid tumors

BACKGROUND

To determine maximum tolerated dose (MTD), recommended dose, safety and pharmacokinetics of irofulven combined with cisplatin in advanced solid tumor patients.

PATIENTS AND METHODS

Cisplatin and irofulven were given sequentially i.v. over 30 min on day 1 and 15 every 4 weeks. Four dose levels (DL) were explored: irofulven (mg/kg)/cisplatin (mg/m2): DL1: 0.3/30; DL2: 0.4/30; DL3: 0.4/40; DL4: 0.5/40. Dose-limiting toxicity (DLT) included dosing omission and delay > 1 week. MTD was the DL with DLT in 2/2 or > or = 2/6 patients during cycle 1-2.

RESULTS

Between March 2002 and April 2003, 33 patients were treated. DLT occurred in 1/6 patients in DL1 (hypomagnesemia, hypocalcemia); 1/6 in DL2 (thrombocytopenia); 2 heavily pretreated patients out of 6 patients in DL3 (neutropenic infection, thrombocytopenia, stomatitis); 2/3 in DL4 (asthenia, blurred vision). Three DLT occurred in 12 additional patients treated at DL2. No toxic deaths occurred; grade 4 toxicity and grade 3 non-hematological toxicity were infrequent. Six patients reported grade 1-2 visual events. Antitumor activity was observed over a broad spectrum of tumor types in all DLs: 1 partial response in bulky sarcoma (DL1); 1 clinical response in endometrial carcinoma (DL1); 2 partial responses not confirmed due to discontinuation (ovarian DL2, renal DL4); 8 stabilizations > 3 months; PSA response: 3/9 prostate cancer patients. Irofulven showed rapid elimination and high interpatient variability. Platinum and irofulven pharmacokinetics did not suggest drug-drug interactions.

CONCLUSION

Irofulven with cisplatin was adequately tolerated and substantial evidence of antitumor activity was observed. The recommended dose is irofulven 0.4 mg/kg and cisplatin 30 mg/m2.

Chemotherapy for metastatic disease: current status

Chemotherapy now has an established role in the treatment of hormone-refractory metastatic prostate cancer. This review summarises the results of the latest trials and discusses ongoing studies investigating the role of chemotherapy earlier in the disease.

Current strategies in the management of hormone refractory prostate cancer

Prostate cancer is the most common cancer diagnosed in American males, and is the second leading cause of cancer-related deaths. Most patients who develop metastatic disease will initially respond to androgen deprivation, but response is invariably temporary. Most patients will develop androgen-independent ("hormone-refractory") disease that results in progressive clinical deterioration and ultimately death. This progression to androgen independence is accompanied by increasingly evident DNA instability and alterations in genes and gene expression, including mutations in p53, over-expression of Bcl2, and mutations in the androgen receptor gene, among others. Treatment options for hormone refractory disease include intensive supportive care, radiotherapy, bisphosphonates, second-line hormonal manipulations, cytotoxic chemotherapy and investigational agents. A post-treatment reduction in the level of prostate specific antigen (PSA) by 50% has been shown to correlate with survival and has been accepted by consensus as a valid endpoint in clinical trials. Chemotherapeutic agents such as mitoxantrone, estramustine, and the taxanes have yielded improved response rates and palliative benefit, but not improved survival. Therefore, current efforts must be focused on enrolling patients onto clinical trials of investigational agents with novel mechanisms of action, and on using survival, time to progression, and quality of life as end points in routine clinical practice.

Carboplatin in advanced hormone refractory prostatic cancer patients

25 patients with measurable or evaluable metastatic prostate cancer, progressive after hormonal treatment, were treated weekly with carboplatin 150 mg/m2 intravenously. The weekly schedule allowed higher dose intensity carboplatin administration with respect to the common monthly cycles. Toxicity was manageable even in elderly patients with extensive bone metastases and consisted primarily of myelosuppression. 4 out of 24 evaluable patients (17%) had a partial response and 12 (50%) had disease stabilisation. The median response duration was 7 months. Prostate-specific antigen and prostatic acid phosphatase serial values showed a correlation with disease response in only 47 and 50% of patients, respectively. These results suggest that carboplatin possesses a moderate but definite activity in prostate cancer patients.