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(1) Background: Markers identifying which patients with metastatic, castration-resistant prostate cancer (mCRPC) will benefit from cabazitaxel therapy are currently lacking. Therefore, the aim of this study was to identify markers associated with outcome to cabazitaxel therapy based on counts and gene expression profiles of circulating tumor cells (CTCs). (2) Methods: From 120 mCRPC patients, CellSearch enriched CTCs were obtained at baseline and after 6 weeks of cabazitaxel therapy. Furthermore, 91 genes associated with prostate cancer were measured in mRNA of these CTCs. (3) Results: In 114 mCRPC patients with an evaluable CTC count, the CTC count was independently associated with poor progression-free survival (PFS) and overall survival (OS) in multivariable analysis with other commonly used variables associated with outcome in mCRPC (age, prostate specific antigen (PSA), alkaline phosphatase, lactate dehydrogenase (LDH), albumin, hemoglobin), together with alkaline phosphatase and hemoglobin. A five-gene expression profile was generated to predict for outcome to cabazitaxel therapy. However, even though this signature was associated with OS in univariate analysis, this was not the case in the multivariate analysis for OS nor for PFS. (4) Conclusion: The established five-gene expression profile in CTCs was not independently associated with PFS nor OS. However, along with alkaline phosphatase and hemoglobin, CTC-count is independently associated with PFS and OS in mCRPC patients who are treated with cabazitaxel.

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The androgen receptor splice variant (AR-V) 7 in circulating tumor cells (CTCs) is a predictor for resistance to anti-AR-targeted treatment, but not to taxane-based chemotherapy in metastatic castration-resistant prostate cancer (mCRPC). In this study, we investigated whether the presence of two constitutively active variants (AR-V3, AR-V7) and two other conditionally activated variants (AR-V1, AR-V9) vs full-length androgen receptor (AR-FL) measured in CTCs from patients with mCRPC were associated with outcome to therapy with the taxane cabazitaxel. Blood was collected at baseline and after two cycles of cabazitaxel from 118 mCRPC patients starting cabazitaxel in a prospective phase II trial. CellSearch-enriched CTCs were enumerated and in parallel characterized for the presence of the AR-Vs by reverse transcription quantitative polymerase chain reaction. Correlations with CTC and prostate-specific antigen response to cabazitaxel as well as associations with overall survival (OS) were investigated. All AR-Vs were frequently present and co-expressed at frequencies of 31-48% at baseline and at 19-40% after two cycles of cabazitaxel. No specific directions of change in the measured variants were detected between the start of treatment and after two cycles of cabazitaxel. No associations between the presence of AR-V3 and AR-V7 and outcome to cabazitaxel were observed. While a reduction in CTCs to < 5 CTCs during treatment (CTC5-response) was less often observed in patients with AR-V9-positive CTCs at baseline (P = 0.004), the CTC5-adjusted detection of AR-V1 after two cycles of cabazitaxel was an independent prognostic factor for OS [HR 2.4 (95% CI 1.1-5.1, P = 0.03)]. These novel findings are expected to contribute to more personalized treatment approaches in mCRPC patients.

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BACKGROUND: Androgen receptor splice variant 7 (AR-V7) in circulating tumor cells (CTCs) from patients with metastatic castration-resistant prostate cancer (mCRPC) was recently demonstrated to be associated with resistance to abiraterone and enzalutamide. Cabazitaxel might, however, remain effective in AR-V7-positive patients. OBJECTIVE: To investigate the association between AR-V7 expression in CTCs and resistance to cabazitaxel. DESIGN, SETTING, AND PARTICIPANTS: We selected patients with mCRPC from the multicenter, randomized, phase 2, randomized, open-label, multicenter study in mCRPC on the pharmacodynamic effects of budesonide on cabazitaxel (Jevtana) (CABARESC). Before the start of the first and third cabazitaxel cycle, CTCs were enumerated using the CellSearch System. In patients with ≥10 CTCs in 7.5 ml blood at baseline, the expression of AR-V7 was assessed by quantitative polymerase chain reaction. OUTCOME MEASURES AND STATISTICAL ANALYSIS: The primary end point was the association between the AR-V7 status and the CTC response rate (decrease to fewer than five CTCs in 7.5 ml blood during treatment). Secondary end points were the prostate-specific antigen (PSA) response rate (RR) and overall survival (OS). Analyses were performed using chi-square and log-rank tests. RESULTS AND LIMITATIONS: AR-V7 was detected in 16 of 29 patients (55%) with ≥10 CTCs and was more frequently found in abiraterone pretreated patients (5 of 5 [100%] treated vs 7 of 20 [35%] untreated; p=0.009). We found no differences in CTC and PSA RRs. The presence of AR-V7 in CTCs was not associated with progression-free survival (hazard ratio [HR]: 0.8; 95% confidence interval [CI], 0.4-1.8) or overall survival (HR 1.6; 95% CI, 0.6-4.4). CONCLUSIONS: The response to cabazitaxel seems to be independent of the AR-V7 status of CTCs from mCRPC patients. Consequently, cabazitaxel might be a valid treatment option for patients with AR-V7-positive CTCs. PATIENT SUMMARY: Tools are needed to select specific treatments for specific patients at specific times. The presence of the gene AR-V7 in CTCs has been associated with resistance to anti-androgen receptor treatments. We investigated whether this holds true for cabazitaxel, but we found cabazitaxel to be effective independent of the presence of AR-V7.

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PURPOSE: Recent data indicate that there is a significant cross-talk between the PI3K/Akt/mTOR and androgen receptor signaling pathways. We evaluated safety and tolerability as well as potential drug-drug interaction of ridaforolimus, a mammalian target of rapamycin (mTOR) inhibitor, when combined with the androgen receptor inhibitor bicalutamide in patients with asymptomatic, metastatic castration-resistant prostate cancer. PATIENTS AND METHODS: Patients were treated with the combination of ridaforolimus 30 mg/day for 5 consecutive days each week and bicalutamide 50 mg/day. Ridaforolimus pharmacokinetics was assessed with and without bicalutamide. RESULTS: Twelve patients were enrolled including 1 screen failure. Dose reductions were required in 7 patients. Three of the 11 patients experienced a dose-limited toxicity, 1 with Grade 3 hyperglycemia and 2 with Grade 2 stomatitis leading to <75 % of planned ridaforolimus dose during the first 35 days of study treatment. The pharmacokinetic results showed no differences in exposures to ridaforolimus with and without concomitant bicalutamide administration. CONCLUSIONS: Although there was no evidence of a clinically relevant pharmacological drug-drug interaction, the occurrence of dose-limiting toxicities in 3 of 11 evaluable patients at a reduced dose of ridaforolimus of 30 mg/day suggests that this combination may not be well suited for asymptomatic or minimally symptomatic prostate cancer patients.

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OBJECTIVE: To determine the efficacy and toxicity of danusertib (formerly PHA-739358) administered i.v. over two different dosing schedules with equivalent dose intensity in patients with metastatic castration-resistant prostate cancer with progressive disease after docetaxel-based treatment. PATIENTS AND METHODS: In this open-label, multicentre phase II trial 88 patients were randomly assigned (1:1 ratio) to receive either danusertib 330 mg/m(2) over 6 h i.v. on days 1, 8 and 15 (arm A, n = 43) or 500 mg/m(2) over 24 h i.v. on days 1 and 15 (arm B, n = 38), every 4 weeks. The primary endpoint chosen for this exploratory study was PSA response rate at 3 months. RESULTS: Sixty patients (31/43 in arm A and 29/38 in arm B) were evaluable for the primary endpoint. Median progression-free survival was 12 weeks in both arms. PSA response occurred in one patient in each arm; best overall response was stable disease in eight (18.6%) and 13 (34.2%) patients in arms A and B, respectively. Eleven out of 81 (13.6%) treated patients had stable disease for ≥6 months. Danusertib was generally well tolerated; the most common grade 3 and 4 drug-related adverse event was neutropenia which occurred in 37.2% (arm A) and 15.8% (arm B) of the patients. CONCLUSION: Danusertib monotherapy shows minimal efficacy in patients with castration-resistant prostate cancer. Further studies are required to establish specific biomarkers predictive for either response or prolonged disease stabilization.

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INTRODUCTION: Drugs that interfere with the normal progression of mitosis belong to the most successful cytotoxic agents currently used for anticancer treatment. Aurora kinases are serine/threonine kinases that function as key regulators of mitosis and are frequently overexpressed in human cancers. The use of several small molecule aurora kinase inhibitors as potential anticancer therapeutic is being investigated. Danusertib (formerly PHA-739358) is a small ATP competitive molecule that inhibits aurora A, B and C kinases. Interestingly, danusertib also inhibits several receptor tyrosine kinases such as Abl, Ret, FGFR-1 and TrkA. These tyrosine kinases are involved in the pathogenesis of a variety of malignancies and the observed multi-target inhibition may increase the antitumor activity resulting in extending the indication. Danusertib was one of the first aurora kinase inhibitors to enter the clinic and has been studied in Phase I and II trials. AREAS COVERED: This review provides an updated summary of preclinical and clinical experience with danusertib up to July 2011. EXPERT OPINION: Future studies with danusertib should focus on the possibility of combining this agent with other targeted anticancer agents, chemotherapy or radiotherapy. As a single agent, danusertib may show more promise in the treatment of leukemias than in solid tumors.

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Colorectal cancer ranks third in incidence in both men and women after lung, breast and prostate cancer. The prevalence of colorectal cancer increases significantly with age, with 40% of patients in Europe being >75 years of age at the time of initial diagnosis. Furthermore, the number of elderly patients with colorectal cancer is expected to increase significantly over the next two decades. Treatment of advanced colorectal cancer has evolved dramatically over the last decade. Advances in surgery and chemotherapy are effective in prolonging time to disease progression and survival in patients with advanced colorectal cancer. For >40 years, fluorouracil has been the mainstay of chemotherapy for advanced colorectal cancer. Recently, however, newer cytotoxic chemotherapies and biological agents effective against colorectal cancer have been shown to improve overall survival in metastatic disease. Thus, a patient with metastatic colorectal cancer today has an expected median survival of 20 months compared with 10 months only a few years ago. There is evidence that elderly individuals derive as much survival benefit from standard chemotherapy approaches in metastatic colorectal cancer as younger patients. Unfortunately, most older patients who might benefit from chemotherapy are not offered this treatment, and the fraction who are not offered it increases with increasing age. Treatment decisions should not be made on the basis of age. Rather, they should be based on functional status, the presence of co-morbidities, and consideration of drug-specific toxicities that can be aggravated in older individuals because of decreased functional reserve. Although the elderly have been under-represented in clinical trials, studies also support the effectiveness of combination chemotherapy in elderly patients with advanced colorectal cancer. This article reviews current optimal first-line treatment strategies for elderly patients with metastatic colorectal cancer.

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In vitro studies suggest that a deficient mismatch repair (MMR) system reduces 5-Fluorouracil cytotoxicity. Colon cancer (CC) in hereditary nonpolyposis colorectal cancer (HNPCC) is due to a dysfunctioning MMR gene that leads to microsatellite instability (MSI). Clinical studies on the efficacy of 5-Fluorouracil (5-FU) in MSI high tumours are contradictory. In a retrospective study, we compared the survival of subjects with stage III CC from HNPCC families that were treated with and without adjuvant 5-FU. The Dutch HNPCC family registry was used. Information on adjuvant chemotherapy for stage III CC was obtained from subjects of families with a mutation and/or who fulfilled the AMS criteria or who were strongly suspicious for HNPCC. CC specific survival was calculated. Observation time was measured either until the date of death, date of a second primary CC or until the closing date of the study, i.e., June 1, 2001. Statistical analysis was done by Kaplan-Meier survival analysis. A total of 92 subjects with stage III CC were included. Twenty-eight of them (17 males) had adjuvant treatment with 5-FU. The median follow-up was 4 (range: 1-17) years; 8 subjects died of CC. The 5-year survival was 70% (95% Cl: 49-90). Sixty-four subjects (36 males) did not have adjuvant therapy. Their median follow-up was 6 (range: 0-23) years. Twenty of them died of CC. The 5-year survival in this group was also 70% (95% Cl: 59-83). To date, the selection of patients with CC for 5-FU treatment is based on the stage rather than the biology of the tumour. In our study, the 5-year survival of subjects treated with and without adjuvant 5-FU did not differ. Further studies are necessary to elucidate the role of MSI in 5-FU treatment of MSI-H tumours in HNPCC.

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