1091 PAIN OUTCOMES IN PATIENTS WITH BONE METASTASES FROM CASTRATE-RESISTANT PROSTATE CANCER: RESULTS FROM A PHASE 3 TRIAL OF DENOSUMAB VS. ZOLEDRONIC ACID

Radiopharmaceuticals for Bone Metastases

As a single organ distributed diffusely throughout the body, bones represent both a unique challenge and unique opportunity for the treatment of symptomatic metastatic disease. While the multifocality of bone metastases often prevents effective complete treatment with focal radiotherapy, the similar pathophysiology of these diffuse sites of disease opens the door to targeted systemic therapy. The relatively rapid dose fall-off from beta- or alpha-emitting particles, if correctly and reliably targeted to osseous metastases, might reduce tumor burden and enhance pain control or improve survival. Radioisotopes have thus been studied keenly with the first generation of primarily beta-emitting radioisotopes, strontium-89 and samarium-153, which reached early FDA approval based on successful endpoints of pain control. More recently, an alpha-emitting therapy, radium-223, has demonstrated a successful endpoint of improved overall survival in patients with a burden of symptomatic, metastatic castrate-resistant prostate cancer (mCRPC) confined to the bones. With this discovery, an additional survival-improving tool beyond systemic and hormonal agents was added to the treatment arsenal for mCRPC for suitable candidates. With an improved understanding of the optimization of hormonal and systemic therapies in the context of mCRPC, there is lingering uncertainty regarding the safety and efficacy of combinatorial use of alpha and beta-emitting therapies with the current generation of systemic agents. In this narrative review, we will highlight the current understanding of the relative utility and clinical paradigms involving alpha- and beta-emitting radioisotopes. We discuss fundamental mechanisms for antineoplastic activity, initial clinical trials validating their use, the use of concurrent antiresorptive therapies to provide bone protection, and ongoing clinical trials targeted at best utilization of these agents in the broader context of mCRPC treatment.

Genome-Based Classification and Therapy of Prostate Cancer

In the past decade, multi-national and multi-center efforts were launched to sequence prostate cancer genomes, transcriptomes, and epigenomes with the aim of discovering the molecular underpinnings of tumorigenesis, cancer progression, and therapy resistance. Multiple biological markers and pathways have been discovered to be tumor drivers, and a molecular classification of prostate cancer is emerging. Here, we highlight crucial findings of these genome-sequencing projects in localized and advanced disease. We recapitulate the utility and limitations of current clinical practices to diagnosis, prognosis, and therapy, and we provide examples of insights generated by the molecular profiling of tumors. Novel treatment concepts based on these molecular alterations are currently being addressed in clinical trials and will lead to an enhanced implementation of precision medicine strategies.

Denosumab treatment in the management of patients with advanced prostate cancer: clinical evidence and experience

Osteoprotective therapies have become an essential component in the management of advanced prostate cancer (PC) patients as bone metastases (BMs) have a major impact on morbidity and mortality. Denosumab is a fully humanized antibody targeting the receptor activator of nuclear factor κB ligand (RANKL), which has been approved by the European Medicines Agency (EMA) in Europe and the United States (US) Food and Drug Administration (FDA) in the US for prevention of skeletal-related events (SREs) in patients with solid tumors and BMs, including PC. The clinical settings in which PC patients should be treated with denosumab are still discussed controversially. In a phase III study, denosumab significantly delayed SREs compared with zoledronic acid (ZA) in patients with metastatic castration-resistant PC (CRPC). In addition, denosumab showed superior effects on pain and health-related quality of life (QoL) in these patients. In patients with nonmetastatic CRPC, denosumab has been proven to significantly increase bone metastases-free survival. However, no significant benefits on cancer-specific and overall survival were observed and denosumab was not approved by the US FDA and EMA in this context. The effectiveness of denosumab in patients with castration-sensitive PC (CSPC) and BMs is also under discussion, as clinical trials with ZA in these patients have not shown significant benefits. Clinical data on the use of denosumab in CSPC are urgently needed.

Advances in prevention and treatment of bone metastases in prostate cancer. Role of RANK/RANKL inhibition

BACKGROUND

Bone metastases are a common complication of prostate cancer, so treatment and prevention are essential to slow the progression of the disease and the occurrence of skeletal related events (SREs), which have devastating consequences for the quality of life of patients.

SUMMARY OF EVIDENCE

Bone metastases are characterized by increased bone turnover and altered balance between osteogenesis and osteolysis, with activation of the RANK and its ligand (RANKL). In patients with metastatic prostate cancer, bisphosphonates have been the bone-targeted agents most commonly used to date. Zoledronic acid has demonstrated efficacy in the reduction and delay of SREs in patients with bone metastases. Denosumab, a RANKL inhibitor, has been demonstrated to be superior to zoledronic acid in the prevention of SREs in castration-resistant prostate cancer (CRPC). Both agents are being considered, along with other new bone-targeted agents, for the prevention of bone metastases in patients with nonmetastatic CRPC, where denosumab has already demonstrated superiority over placebo.

CONCLUSIONS

Denosumab and zoledronic acid prevent SREs in patients with prostate cancer and bone metastases. Denosumab also has a potential role in delaying bone metastases in nonmetastatic patients. Advances in the treatment of CRPC include an increasing focus on prevention of the progression of bone disease.

Denosumab for treatment of bone metastases secondary to solid tumours: systematic review and network meta-analysis

AIM

To evaluate the evidence for denosumab for the treatment of bone metastases secondary to solid tumours and, using a network meta-analysis, indirectly compare denosumab with bisphosphonates and best supportive care.

DATA SOURCES

MEDLINE (1948 to April 2011), EMBASE (1980 to March 2011), Cochrane Library (all sections) (issue 1, 2011) and Web of Science with Conference Proceedings (1970 to May 2011) and additional meeting abstracts (2010 and 2011) were searched. STUDY ELIGIBILITY, PARTICIPANTS AND INTERVENTIONS: Only randomised controlled trials assessing denosumab, bisphosphonates or best supportive care in patients with bone metastases from any solid tumour were included.

SYNTHESIS

Direct evidence comparing denosumab and zoledronic acid was assessed for breast cancer, prostate cancer and other solid tumours. Denosumab was compared with pamidronate and best supportive care through a network meta-analysis for each tumour type. The primary outcomes were time to first skeletal related event (SRE) and time to first and subsequent SRE. Secondary outcomes were skeletal morbidity rate, pain, quality of life (QoL) and overall survival.

RESULTS

Denosumab was found to be more effective in delaying the time to first SRE and reducing the risk of first and subsequent SRE compared to zoledronic acid, placebo and pamidronate. In breast and prostate cancer, denosumab was effective in reducing skeletal morbidity rate compared with placebo. The lack of published data on pain and QoL meant that firm conclusions could not be made. Denosumab did not appear to have an affect on overall survival.

LIMITATIONS

Network meta-analyses are subject to uncertainties and potential biases.

CONCLUSIONS

Denosumab is effective in preventing SRE, but the effect on pain and QoL is unclear.

Denosumab in patients with cancer and skeletal metastases: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review of the literature to determine the efficacy and safety of denosumab in reducing skeletal-related events (SRE) in patients with bone metastases.

METHODS

A literature search using MEDLINE, EMBASE, Web of Science and The Cochrane Collaboration Library identified relevant controlled clinical trials up-to-March 14, 2012. Two independent reviewers assessed studies for inclusion, according to predetermined criteria, and extracted relevant data. The primary outcomes of interest were SRE, time to first on-study SRE, and overall survival. Secondary outcomes included pain, quality of life, bone turnover markers (BTM), and adverse events.

RESULTS

Six controlled trials including 6142 patients were analyzed. Compared to zoledronic acid, denosumab had lower incidence of SRE with a risk ratio (RR) of 0.84 (95% confidence intervals (CI) 0.80-0.88), delayed the onset of first on-study SRE (RR 0.83; 95% CI 0.75-0.90) and time to worsening of pain (RR 0.84; 95% CI 0.77-0.91). No difference was observed in overall survival with pooled hazard ratio of 0.98 (95% CI 0.90-1.0). For total adverse events, denosumab was similar to zoledronic acid (RR 0.97; 95% CI 0.89-1.0). No significant differences were observed in the frequency of osteonecrosis of the jaw (RR 1.4; 95% CI 0.92-2.1). Patients on denosumab had a greater risk of developing hypocalcemia (RR 1.9; 95% CI 1.6-2.3).

CONCLUSIONS

Denosumab was more effective than zoledronic acid in reducing the incidence of SRE, and delayed the time to SRE. No differences were found between denosumab and zoledronic acid in reducing overall mortality, or in the frequency of overall adverse events.