This first-in-man imaging study evaluated the safety and feasibility of hyperpolarized [1-13C]pyruvate as an agent for noninvasively characterizing alterations in tumor metabolism for patients with prostate cancer. Imaging living systems with hyperpolarized agents can result in more than 10,000-fold enhancement in signal relative to conventional magnetic resonance (MR) imaging. When combined with the rapid acquisition of in vivo 13C MR data, it is possible to evaluate the distribution of agents such as [1-13C]pyruvate and its metabolic products lactate, alanine, and bicarbonate in a matter of seconds. Preclinical studies in cancer models have detected elevated levels of hyperpolarized [1-13C]lactate in tumor, with the ratio of [1-13C]lactate/[1-13C]pyruvate being increased in high-grade tumors and decreased after successful treatment. Translation of this technology into humans was achieved by modifying the instrument that generates the hyperpolarized agent, constructing specialized radio frequency coils to detect 13C nuclei, and developing new pulse sequences to efficiently capture the signal. The study population comprised patients with biopsy-proven prostate cancer, with 31 subjects being injected with hyperpolarized [1-13C]pyruvate. The median time to deliver the agent was 66 s, and uptake was observed about 20 s after injection. No dose-limiting toxicities were observed, and the highest dose (0.43 ml/kg of 230 mM agent) gave the best signal-to-noise ratio for hyperpolarized [1-13C]pyruvate. The results were extremely promising in not only confirming the safety of the agent but also showing elevated [1-13C]lactate/[1-13C]pyruvate in regions of biopsy-proven cancer. These findings will be valuable for noninvasive cancer diagnosis and treatment monitoring in future clinical trials.

Purpose Clinical features characteristic of small-cell prostate carcinoma (SCPC), (““anaplastic””) often emerge during the progression of prostate cancer. We sought to determine the efficacy of platinum-based chemotherapy in patients meeting at least one of seven prospectively defined “anaplastic” clinical criteria, including exclusive visceral or predominantly lytic bone metastases, bulky tumor masses, low PSA levels relative to tumor burden or short response to androgen deprivation therapy. Experimental Design A 120-patient phase II trial of frontline carboplatin and docetaxel (CD) and second-line etoposide and cisplatin (EP) was designed to provide reliable clinical response estimates under a Bayesian probability model with early stopping rules in place for futility and toxicity. Results Seventy-four of 113 (65.4%) and 24 of 71 (33.8%) were progression free after 4 cycles of CD and EP, respectively. Median overall survival (OS) was 16 months (95% CI, 13.6-19.0 months). Of the 7 “anaplastic” criteria, bulky tumor mass was significantly associated with poor outcome. Lactic acid dehydrogenase (LDH) strongly predicted for OS and rapid progression. Serum carcinoembryonic antigen (CEA) concentration strongly predicted OS but not rapid progression. Neuroendocrine markers did not predict outcome or response to therapy. Conclusion Our findings support the hypothesis that patients with “anaplastic” prostate cancer are a recognizable subset characterized by a high response rate of short duration to platinum-containing chemotherapies, similar to SCPC. Our results suggest that CEA is useful for selecting therapy in men with CRPC and consolidative therapies to bulky high-grade tumor masses should be considered in this patient population.

In mCRPC patients, ipilimumab 10 mg/kg ± radiotherapy suggested clinical antitumor activity with disease control and manageable AEs. Two phase III trials in mCRPC patients evaluating ipilimumab 10 mg/kg ± radiotherapy are ongoing. ClinicalTrials.gov identifier: NCT00323882.

Purpose Cabozantinib (XL184) is an orally bioavailable tyrosine kinase inhibitor with activity against MET and vascular endothelial growth factor receptor 2. We evaluated the activity of cabozantinib in patients with castration-resistant prostate cancer (CRPC) in a phase II randomized discontinuation trial with an expansion cohort. Patients and Methods Patients received 100 mg of cabozantinib daily. Those with stable disease per RECIST at 12 weeks were randomly assigned to cabozantinib or placebo. Primary end points were objective response rate at 12 weeks and progression-free survival (PFS) after random assignment. Results One hundred seventy-one men with CRPC were enrolled. Random assignment was halted early based on the observed activity of cabozantinib. Seventy-two percent of patients had regression in soft tissue lesions, whereas 68% of evaluable patients had improvement on bone scan, including complete resolution in 12%. The objective response rate at 12 weeks was 5%, with stable disease in 75% of patients. Thirty-one patients with stable disease at week 12 were randomly assigned. Median PFS was 23.9 weeks (95% CI, 10.7 to 62.4 weeks) with cabozantinib and 5.9 weeks (95% CI, 5.4 to 6.6 weeks) with placebo (hazard ratio, 0.12; P < .001). Serum total alkaline phosphatase and plasma cross-linked C-terminal telopeptide of type I collagen were reduced by ≥ 50% in 57% of evaluable patients. On retrospective review, bone pain improved in 67% of evaluable patients, with a decrease in narcotic use in 56%. The most common grade 3 adverse events were fatigue (16%), hypertension (12%), and hand-foot syndrome (8%). Conclusion Cabozantinib has clinical activity in men with CRPC, including reduction of soft tissue lesions, improvement in PFS, resolution of bone scans, and reductions in bone turnover markers, pain, and narcotic use.