Efficacy, quality of life, and safety of cabazitaxel in Canadian metastatic castration-resistant prostate cancer patients treated or not with prior abiraterone

Preclinical Models in Prostate Cancer: Resistance to AR Targeting Therapies in Prostate Cancer

Prostate cancer is an androgen-driven tumor. Different prostate cancer therapies consequently focus on blocking the androgen receptor pathway. Clinical studies reported tumor resistance mechanisms by reactivating and bypassing the androgen pathway. Preclinical models allowed the identification, confirmation, and thorough study of these pathways. This review looks into the current and future role of preclinical models to understand resistance to androgen receptor-targeted therapies. Increasing knowledge on this resistance will greatly improve insights into tumor pathophysiology and future treatment strategies in prostate cancer.

Neutropenia Prevention in the Treatment of Post-docetaxel Metastatic, Castration-resistant Prostate Cancer With Cabazitaxel and Prednisone: A Multicenter, Open-label, Single-arm Phase IV Study

INTRODUCTION

Severe neutropenia is a dose-limiting factor that occurs in up to 82% of patients with metastatic castration-resistant prostate cancer (mCRPC) treated with cabazitaxel. This study evaluated the effectiveness of granulocyte colony-stimulating factor (G-CSF) plus ciprofloxacin as prophylaxis in post-docetaxel patients with mCRPC treated with cabazitaxel and at high risk for neutropenia.

PATIENTS AND METHODS

This was a phase IV, multicenter, open-label, single-arm interventional study with men aged ≥ 65 years (or < 65 years and ≥ 25% irradiated bone marrow), presenting with mCRPC after docetaxel failure, performance status ≤ 1, and life expectancy > 12 weeks. Cabazitaxel 25 mg/m² and prednisone were given on day 1, every 21 days. G-CSF was administered on days 2 to 8 of each cycle or until an absolute neutrophil count > 2000/mm³, and ciprofloxacin 1000 mg was given orally on days 5 to 12. The rate of neutropenia grade ≥ 3 during the first cycle (primary endpoint), and frequency of neutropenia grade ≥ 3, febrile neutropenia, diarrhea grade ≥ 3, prostate-specific antigen response, and quality of life during treatment (secondary end points) were estimated.

RESULTS

We included 46 patients. The mean number of cabazitaxel cycles was 9.5. During the first cycle, 40.0% of patients had neutropenia grade ≥ 3, and 42.2% had at least 1 episode of neutropenia during treatment. Febrile neutropenia and diarrhea grade ≥ 3 occurred in 1 patient each. Twenty-nine (64.4%) patients achieved prostate-specific antigen response, and 77.2% improved quality of life scores in at least 1 visit.

CONCLUSIONS

Prophylactic G-CSF was effective in preventing neutropenia grade ≥ 3 and other hematologic complications during treatment with cabazitaxel 25 mg/m² in post-docetaxel patients with mCRPC at high risk for neutropenia. The role of prophyclatic ciprofloxacin to prevent febrile neutropenia in this setting is still unclear and needs to be further evaluated.

Abiraterone vs. docetaxel for metastatic hormone-sensitive prostate cancer: A microsimulation model

INTRODUCTION

Our aim was to determine whether androgen deprivation therapy (ADT) with abiraterone acetate (AA) or ADT with docetaxel chemotherapy (DC) resulted in improved quality-adjusted life years (QALYs) among men with de novo metastatic castration-sensitive prostate cancer (mCSPC) and the cost effectiveness of the preferred strategy using decision analytic techniques.

METHODS

A microsimulation model with a lifetime time horizon was constructed. Our primary outcome was QALYs. Secondary outcomes included cost, incremental cost effectiveness ratio (ICER), unadjusted overall survival (OS), rates of second- and third-line therapy, and adverse events. A systematic literature review was used to generate probabilities and utilities to populate the model. The base case was a 65-year-old patient with de novo mCSPC.

RESULTS

A total of 100 000 microsimulations were generated. Initial AA resulted in a gain of 0.45 QALYs compared to DC (3.36 vs. 2.91 QALYs) with an ICER of $276 251.82 per QALY gained with initial AA therapy. Median crude OS was 51 months with AA and 48 months with DC. Overall, 46.6% and 42.6% of patients received second-line therapy and 8.7% and 7.9% patients received third-line therapy in the AA and DC groups, respectively. Grade 3/4 adverse events were experienced in 17.6% of patients receiving initial AA and 22.3% of patients receiving initial DC.

CONCLUSIONS

Although ADT with AA results in a gain in QALYs and crude OS compared to DC, AA therapy is not a cost-effective treatment strategy to apply uniformly to all patients. The availability of AA as a generic medication may help to close this gap. The ultimate choice should be based on patient and tumor factors.

Metastatic prostate cancer remains incurable, why?

Metastatic prostate cancer patients present in two ways-with already disseminated disease at the time of presentation or with disease recurrence after definitive local therapy. Androgen deprivation therapy is given as the most effective initial treatment to patients. However, after the initial response, almost all patients will eventually progress despite the low levels of testosterone. Disease at this stage is termed castration resistant prostate cancer (CRPC). Before 2010, the taxane docetaxel was the first and only life prolonging agent for metastatic CRPC (mCRPC). The last decade has witnessed robust progress in CRPC therapeutics development. Abiraterone, enzalutamide, apalutamide and sipuleucel-T have been evaluated as first- and second-line agents in mCRPC patients, while cabazitaxel was approved as a second-line treatment. Radium-223 dichloride was approved in symptomatic patients with bone metastases and no known visceral metastases pre- and post-docetaxel. However, despite significant advances, mCRPC remains a lethal disease. Both primary and acquired resistance have been observed in CRPC patients treated by these new agents. It could be solely cell intrinsic or it is possible that the clonal heterogeneity in treated tumors may result from the adaptive responses to the selective pressures within the tumor microenvironment. The aim of this review is to list current treatment agents of CRPC and summarize recent findings in therapeutic resistance mechanisms.

Prognostic and predictive clinical factors in patients with metastatic castration-resistant prostate cancer treated with cabazitaxel

INTRODUCTION

Cabazitaxel is one of several treatment options available for patients with metastatic castration-resistant prostate cancer who have progressed on docetaxel. Little is known about clinical factors that influence prognosis or treatment response for patients receiving cabazitaxel. Identifying prognostic and predictive factors could contribute to the optimal selection of patients for treatment after docetaxel.

METHODS

A retrospective review of patients enrolled on the cabazitaxel Canadian Early Access Program (C-EAP) was performed. Clinical factors were analyzed by univariable and multivariable Cox proportional hazards and logistic regression analysis to identify independent predictors of prognosis and response.

RESULTS

Forty-five patients from five centres in Canada were included in this study. On multivariable analysis, lower hemoglobin was associated with shorter survival. No other factors were independently associated with survival, prostate-specific antigen (PSA) response, or primary PSA progression.

CONCLUSIONS

Clinical factors predicting survival or treatment response were not identified for men with castration-resistant prostate cancer receiving cabazitaxel. Larger studies may be necessary to identify clinical factors and biomarkers that identify whether patients should or should not receive cabazitaxel.

The evolution of chemotherapy for the treatment of prostate cancer

Chemotherapy has been explored as a treatment option for metastatic prostate cancer since the early 1980s. Docetaxel, a taxane chemotherapeutic, was approved for the treatment of men with metastatic castration-resistant prostate cancer in 2004, and is now standard of care for late stage disease. Recent clinical studies demonstrated that patients with metastatic castration-sensitive disease, and possibly those with high-risk localized prostate cancer also benefit from docetaxel administration, expanding the role of chemotherapy in the prostate cancer treatment landscape. Another taxane, cabazitaxel, is approved for post-docetaxel metastatic castration-resistant prostate cancer. Taxanes and other chemotherapeutics, such as carboplatin, are now being tested in combination regimens. This review presents an outline of recent and ongoing clinical studies assessing docetaxel and its derivative cabazitaxel at different stages of the disease, and in various combinations with other agents. We summarize current knowledge on biomarkers predictive of response to chemotherapy, which may in future be used to guide individualized treatment decisions.

Quality of Life in Second-Line Treatment of Metastatic Castration-Resistant Prostate Cancer Using Cabazitaxel or Other Therapies After Previous Docetaxel Chemotherapy: Swiss Observational Treatment Registry

BACKGROUND

The aim was to evaluate quality of life (QoL), pain, and fatigue in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with different regimens after first-line docetaxel, as well as disease progression.

PATIENTS AND METHODS

Patients with mCRPC having received first-line chemotherapy with docetaxel were eligible. Second-line treatment choice was at the discretion of the local investigator. All patients had regular assessments of QoL with the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire, of fatigue with the Brief Fatigue Inventory, and of pain with the McGill Pain Questionnaire-Short Form. The primary end point was QoL maintenance defined as having a maximum decrease in 2 functional domains of the FACT-P.

RESULTS

One hundred thirty-eight patients were included in 36 oncology centers across Switzerland. QoL analysis was available for all patients (59 who received cabazitaxel; 79 who received other therapy [OT] including 75 who received abiraterone). No significant differences for any of the end points were found between groups. A numerically higher number of patients had QoL maintenance with OT (25 of 79 patients, 32%) compared with cabazitaxel (8 of 59 patients, 14%). QoL improvement was found in 20% of patients (12 of 59) who received cabazitaxel and 24% (19 of 79) who received OT. Mean FACT-P score did not change in a clinically relevant manner over time in either group. Pain was present in 70% of patients (96 of 138), and a pain response to treatment was noted in 22% (13 of 59) who received cabazitaxel and 29% (23 of 79) who received OT. A similar but minor improvement of fatigue was noted in both groups.

CONCLUSION

Some degree of QoL decrease was seen in most patients regardless of second-line treatment. No significant differences in QoL parameters between cabazitaxel or other second line treatments were found.

Cabazitaxel in patients with metastatic castration-resistant prostate cancer: safety and quality of life data from the Australian early access program

AIM

Cabazitaxel is a next generation taxane that has been shown to improve overall survival in patients with metastatic castration-resistant prostate cancer (mCRPC) whose disease progressed during or after docetaxel-based therapy. A worldwide early access program (EAP) study was established to provide access to cabazitaxel ahead of commercial availability and to evaluate its safety and tolerability. The Australian EAP included patient-reported outcomes to evaluate the impact of cabazitaxel on quality of life (QoL). The final safety and QoL results from the Australian EAP for cabazitaxel are reported.

METHODS

Australian patients with mCRPC previously treated with a docetaxel-containing regimen received cabazitaxel (25 mg/m² ) every 3 weeks plus prednisone/prednisolone (10 mg daily) until disease progression, death, unacceptable toxicity, physician's decision or patient's refusal of further treatment. QoL data was collected using the AQoL-8D questionnaire.

RESULTS

104 patients from 18 Australian sites (median age at baseline, 70) enrolled in the EAP and completed at least one AQoL-8D questionnaire. Patients received a median of 6 cycles of cabazitaxel. 67 patients (64.4%) experienced grade ≥3 treatment-emergent adverse events (TEAEs); the most frequent TEAEs were neutropenia, febrile neutropenia, diarrhoea, and vomiting. QoL scores remained stable with increasing treatment cycles.

CONCLUSION

The results suggest that the safety profile cabazitaxel is manageable in the Australian clinical practice setting and that QoL is maintained with little or no detrimental effect of cabazitaxel in patients continuing on treatment without disease progression.