Thalidomide/Estramustine/Paclitaxel in Metastatic Androgen-Independent Prostate Cancer

A modular Phase I study of lenalidomide and paclitaxel in metastatic castration-resistant prostate cancer following prior taxane therapy

PURPOSE

Lenalidomide, a highly potent immunomodulatory derivative of thalidomide, potentiates the action of paclitaxel in vitro against prostate cancer cell lines in co-culture with mononuclear cells. A modular Phase I study of lenalidomide and paclitaxel in men with metastatic castration-resistant prostate cancer (CRPC) was conducted to assess PSA kinetics with lead-in lenalidomide and the feasibility of the combination.

METHODS

Men with metastatic CRPC with prior taxane chemotherapy were planned for single-agent "lead-in" lenalidomide for 21/28 days at dose-levels: -1 (5 mg), 0 (10 mg), +1 (15 mg), +2 (20 mg), +3 (25 mg); followed by lenalidomide at the same dose and schedule in combination with weekly intravenous paclitaxel 100 mg/m(2) over 3 h on days 1, 8, 15 every 28 days utilizing a 3 + 3 dose-escalation design.

RESULTS

Dose-limiting toxicity was observed in 4/6 patients with first-cycle combination therapy at the 10 mg dose-level and 3/6 patients at the 5 mg dose-level of lenalidomide, respectively. These included Grade 3 neutropenia precluding planned paclitaxel therapy (n = 3), grade 3 gastrointestinal toxicity (n = 2), chest pain (n = 1) and pulmonary embolism (n = 1). With lead-in lenalidomide, two patients with lymph-node dominant CRPC had a PSA-decline and regression in lymph node disease, respectively. Two of seven evaluable patients had PSA declines by 50% with combination therapy. Progression-free survival was 13 weeks (range 4-35 weeks).

CONCLUSIONS

The high dose-limiting toxicity rates observed with lenalidomide and weekly paclitaxel require exploration of alternate dose-schedules of the combination in the second-line setting of CRPC. These early observations suggest distinctive toxicity and efficacy outcomes from thalidomide in combination with paclitaxel.

Therapeutic options for hormone-refractory prostate cancer in 2007

Prostate cancer is the most commonly diagnosed cancer in American men and a major health problem. While localized disease has an excellent chance for cure, metastatic disease leads to androgen-independent progression and death within a few years. Although docetaxel represents an important therapeutic milestone and is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC), most patients eventually progress because of clonal selection of therapy-resistant cells or the development of cells with a drug-resistant phenotype. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy, the rational design of targeted therapeutics is possible. Over the last few years, many gene targets that regulate apoptosis, proliferation, and cell signalling have been identified, and numerous novel compounds have entered clinical trials either as single agents or in combination with cytotoxic chemotherapy. Neoadjuvant trials in particular must be further encouraged since they allow detection of biological activity in the prostatectomy specimen. This article reviews new treatment options available for men with advanced prostate cancer. Even though HRPC remains incurable, it is not untreatable. Recent findings are very promising, but challenges remain in demonstrating effective anti-tumor activity and showing a clinically relevant survival benefit in Phase III trials.

Taxane refractory prostate cancer

PURPOSE

Although docetaxel based therapy has become established as a front line therapy choice based on large, randomized studies, published studies of second line therapy for taxane refractory disease are limited.

MATERIAL AND METHODS

The literature on the biology of taxane resistance and studies applied to prostate cancer were reviewed using a PubMed(R) search and proceedings from recent symposia.

RESULTS

Although taxane resistance invariably emerges in the treatment of prostate cancer, a consensus working definition or classification does not exist. Although there is a body of knowledge on the mechanisms of action of taxanes and resistance pathways, there are few clinical or translational studies in prostate cancer adequately assessing the modulation of these mechanisms. Results of additional clinical trials are needed to define and improve the standard of care in the second line setting for castration resistant prostate cancer after docetaxel failure.

CONCLUSIONS

The validation of the microtubule as a target in prostate cancer implies that a finer understanding of specific mechanisms of efficacy and resistance may yield novel strategies. Taxane analogues that have greater antitumor activity and/or are less susceptible to drug resistance mechanisms than their prototypes are in development, as are nontaxane microtubule targeting agents and other agents directed against the mitotic spindle. Combinations of such agents may yield added efficacy but potentially added neurotoxicity. In contrast, combinations with drugs that inhibit cellular mechanisms of taxane resistance and vascular endothelial or tumor-stromal prosurvival interactions may have lower neurotoxic profiles. Although alternate classes of cytotoxic agents, eg satraplatin, are being studied, there is a strong imperative for translational studies in this setting.

Novel targets and approaches in advanced prostate cancer

PURPOSE OF REVIEW

The development of therapeutic resistance is the underlying cause for most cancer deaths. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in prostate cancer, the rational design of targeted therapeutics is possible. We review new treatment options for men with advanced prostate cancer.

RECENT FINDINGS

Although the taxanes currently represent the most active chemotherapeutic agents and standard of care for first-line treatment of metastatic hormone-refractory prostate cancer, most patients eventually progress because of intrinsic or acquired drug resistance. In recent years, increased knowledge of cancer progression and therapeutic resistance has identified many gene targets that regulate apoptosis, proliferation, and cell signalling. To date, numerous novel compounds have entered clinical trials as either single agents or in combination with cytotoxic chemotherapy.

SUMMARY

Even though hormone-refractory prostate cancer is still incurable, it is not untreatable. As cancer cells are proficient at adapting to therapeutic stressors, a combination regimen with drugs that target crucial cellular networks like the apoptotic rheostat may be more promising than treatment with highly selective single-target agents. Recent findings are very hopeful, but challenges remain to demonstrate effective antitumour activity in phase III trials with survival as the principal endpoint.