Estimating survival benefit in castrate metastatic prostate cancer: decision making in proceeding to a definitive phase III trial

Patient selection for phase II trials

The standard phase II trial design yields disparate results with similar regimens owing, in part, to variable patient populations enrolled, and appears to be a poor indicator of efficacy demonstrable in a phase III trial. While other phase II trial designs attempt to rectify this problem including the randomized phase II trial and randomized discontinuation trial, they demand more resources and a larger number of patients and are not definitive. A paradigm of multicenter straight phase II trials with rigorous attention to patient selection criteria to improve the validity and reproducibility of results is proposed. Such trials may be superior guides to select regimens for further development than trials that are single-center based with favorable populations.

Weekly paclitaxel and high-dose 5-fluorouracil plus leucovorin in hormone-refractory prostate cancer: In vitro combined effects and a Phase II trial

PURPOSE

Paclitaxel and 5-fluorouracil have been used to treat hormone-refractory prostate cancer with some success. In vitro data suggest that the combined cytotoxicity may be sequence dependent. Thus, we explored the combined effects of the 2 agents, both in vitro and in vivo.

PATIENTS AND METHODS

The combined cytotoxicity of paclitaxel and 5-fluorouracil, and the possible schedule dependence were studied in vitro using PC-3 and DU145 cells and the microculture tetrazolium assay. There were 23 patients with hormone-refractory prostate cancer treated with the regimen T-HDFL: paclitaxel 90 mg/m2 intravenously 1 hour on days 1 and 8; 5-fluorouracil 2000 mg/m2; and leucovorin 300 mg/m2 intravenous 24-hour infusion on days 2 and 9, which repeated every 21 days. The allowed percentage of bone marrow irradiation was 50%.

RESULTS

Significant synergistic cytotoxicity was seen only when paclitaxel was given 24 hours before 5-fluorouracil. With the T-HDFL regimen, 11 (52%) of the 21 evaluable patients had > or = 50% reduction of prostate-specific antigen, lasting for 6 weeks. Of the 7 patients with measurable disease, 2 had a partial response. Median overall survival was 14.1 months. Grade III/IV leukopenia occurred in 2 patients. There was no treatment-related death. Toxicities were well tolerated.

CONCLUSIONS

The combined cytotoxicity of paclitaxel and 5-fluorouracil is schedule dependent. It is feasible to administer weekly paclitaxel and high-dose 5-fluorouracil infusions in patients with hormone-refractory prostate cancer. Our findings may serve as an important rationale for future trial design.

The Association Between Measures of Progression and Survival in Castrate-Metastatic Prostate Cancer

PURPOSE

To explore the association between progression-free survival and overall survival time in patients with castration-resistant prostate cancer treated with microtubule-targeted therapies.

EXPERIMENTAL DESIGN

We retrospectively studied patients treated in three trials evaluating a taxane or an epothilone for progressive castration-resistant prostate cancer. Study subjects were 98 patients with bone metastases; 63 of them also had soft tissue lesions. All scans were reviewed independently. Associations of radiographic progression-free survival and prostate-specific antigen (PSA) progression-free survival with survival time were measured using Kendall's tau, adjusted for right censoring. A smoothing procedure was applied to estimate Kendall's tau within each neighborhood of the follow-up process.

RESULTS

The overall associations between progression-free survival time and overall survival time were moderate: 0.4 for radiographic progression-free survival and 0.33 for PSA progression-free survival. The association between radiographic progression-free survival and overall survival was weakest early in the follow-up process, whereas the PSA association was weakest when the progression-free survival-related event (PSA progression, death, or censoring) occurred after 6 months from the start of treatment.

CONCLUSIONS

Current measures of progression-free survival time for men with castration-resistant prostate cancer are not strongly concordant with survival time. Factors that attenuate the association include interval censoring and the discontinuation of therapy early in the follow-up due to imaging changes that may not reflect true failure of the treatment. For radiographic progression-free survival, the association may be increased by requiring confirmation of progression with a second scan, as is routinely done when assessing response.

A phase II study of weekly paclitaxel/estramustine/carboplatin in hormone-refractory prostate cancer

PURPOSE

The objective of this phase II study was to determine the response rate in patients with hormone-refractory prostate cancer given paclitaxel/estramustine/carboplatin for weeks 1, 2, and 3 of a 4-week cycle.

PATIENTS AND METHODS

Eighty-four patients were registered into the trial. Paclitaxel 80 mg/m2 and carboplatin area under the curve of 2 were administered intravenously on days 2, 9, and 16, and oral estramustine 280 mg 3 times daily was given on days 1-3, 8-10, and 15-17 for 6 cycles. Eastern Cooperative Oncology Group performance status 0, 1, and 2 was 46%, 41%, and 13%, respectively, and median age was 70 years (range, 53-82 years), with 58 patients (69%) aged > 65 years. The majority of patients (83%) were white. Fifteen patients (18%) had received previous chemotherapy, 61 patients (73%) had undergone previous surgery, and 51 patients (61%) had received previous external-beam radiation therapy.

RESULTS

Intent-to-treat analysis revealed a > or = 50% prostate-specific antigen decrease rate of 61%. Median survival was 15.3 months. The most frequent grade > or = 3 toxicities included fatigue (11%), nausea (10%), neutropenia (9%), anemia (6%), and vomiting (6%).

CONCLUSION

Paclitaxel/estramustine/carboplatin administered in a weekly regimen is highly effective in the treatment of hormone-refractory prostate cancer and can be administered with reasonable safety in an outpatient setting.

Progress and promise of FDG-PET imaging for cancer patient management and oncologic drug development

2-[(18)F]Fluoro-2-deoxyglucose positron emission tomography (FDG-PET) assesses a fundamental property of neoplasia, the Warburg effect. This molecular imaging technique offers a complementary approach to anatomic imaging that is more sensitive and specific in certain cancers. FDG-PET has been widely applied in oncology primarily as a staging and restaging tool that can guide patient care. However, because it accurately detects recurrent or residual disease, FDG-PET also has significant potential for assessing therapy response. In this regard, it can improve patient management by identifying responders early, before tumor size is reduced; nonresponders could discontinue futile therapy. Moreover, a reduction in the FDG-PET signal within days or weeks of initiating therapy (e.g., in lymphoma, non-small cell lung, and esophageal cancer) significantly correlates with prolonged survival and other clinical end points now used in drug approvals. These findings suggest that FDG-PET could facilitate drug development as an early surrogate of clinical benefit. This article reviews the scientific basis of FDG-PET and its development and application as a valuable oncology imaging tool. Its potential to facilitate drug development in seven oncologic settings (lung, lymphoma, breast, prostate, sarcoma, colorectal, and ovary) is addressed. Recommendations include initial validation against approved therapies, retrospective analyses to define the magnitude of change indicative of response, further prospective validation as a surrogate of clinical benefit, and application as a phase II/III trial end point to accelerate evaluation and approval of novel regimens and therapies.

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

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