Turbulent Drag Reduction by Flexible and Rodlike Polymers: Crossover Effects at Small Concentrations

Drag reduction by polymers is bounded between two universal asymptotes, the von-K\'arm\'an log-law of the law and the Maximum Drag Reduction (MDR) asymptote. It is theoretically understood why the MDR asymptote is universal, independent of whether the polymers are flexible or rodlike. The cross-over behavior from the Newtonian von-K\'arm\'an log-law to the MDR is however not universal, showing different characteristics for flexible and rodlike polymers. In this paper we provide a theory for this cross-over phenomenology.Comment: 5 pages, 4 figures, submitted to Physical Review

Colloquium: Theory of Drag Reduction by Polymers in Wall Bounded Turbulence

The flow of fluids in channels, pipes or ducts, as in any other wall-bounded flow (like water along the hulls of ships or air on airplanes) is hindered by a drag, which increases many-folds when the fluid flow turns from laminar to turbulent. A major technological problem is how to reduce this drag in order to minimize the expense of transporting fluids like oil in pipelines, or to move ships in the ocean. It was discovered in the mid-twentieth century that minute concentrations of polymers can reduce the drag in turbulent flows by up to 80%. While experimental knowledge had accumulated over the years, the fundamental theory of drag reduction by polymers remained elusive for a long time, with arguments raging whether this is a "skin" or a "bulk" effect. In this colloquium review we first summarize the phenomenology of drag reduction by polymers, stressing both its universal and non-universal aspects, and then proceed to review a recent theory that provides a quantitative explanation of all the known phenomenology. We treat both flexible and rod-like polymers, explaining the existence of universal properties like the Maximum Drag Reduction (MDR) asymptote, as well as non-universal cross-over phenomena that depend on the Reynolds number, on the nature of the polymer and on its concentration. Finally we also discuss other agents for drag reduction with a stress on the important example of bubbles.Comment: Invited Colloquium Paper for Reviews of Modern Physics, 24 pages, 18 Figs., submitte

Sunitinib and other targeted therapies for renal cell carcinoma

Targeted therapy has radically altered the way metastatic renal cancer is treated. Six drugs are now licensed in this setting, with several other agents under evaluation. Sunitinib is currently the most widely used in the first line setting with impressive efficacy and an established toxicity profile. However, as further randomised studies report and as newer drugs become available this may change. In this review, we address our current understanding of targeted therapy in renal cancer. We also discuss areas in which our knowledge is incomplete, including the identification of correlative biomarkers and mechanisms of drug resistance. Finally, we will describe the major areas of clinical research that will report over the next few years

Long-term Safety of Sunitinib in Metastatic Renal Cell Carcinoma

Background Metastatic renal cell carcinoma (mRCC) patients receiving first-line sunitinib typically survive >2 yr, with chronic treatment sometimes extending to ≥6 yr. Objective To analyze long-term safety with sunitinib in mRCC patients. Design, setting, and participants Data were pooled from 5739 patients in nine trials, comprising seven phase II studies, a phase III study, and an expanded-access trial in various treatment settings (e.g. cytokine refractory or treatment-naïve). Outcome measurements and statistical analysis Interval and cumulative time-period analyses evaluated the incidence of treatment-related adverse events (TRAEs) for up to 6 yr, in the overall population and in those with long-term (≥2 yr) sunitinib treatment. Results and limitations Among long-term patients (n=807), most TRAEs occurred initially in the first year and then decreased in frequency; TRAEs following this pattern included decreased appetite, diarrhea, dysgeusia, dyspepsia, fatigue, hypertension, mucosal inflammation, nausea, and stomatitis. However, hypothyroidism increased by interval analysis from 6% at 0-<6 mo to 42% at 5-<6 yr and by cumulative analysis from 14% at 0-<1 yr to 36% over 6 yr. Grade 3/4 TRAEs in long-term patients peaked during the first year and then steadily decreased. The overall population displayed only minor differences from long-term patients, with no clinically significant differences between grade ≥3 TRAE profiles (<5% difference in incidence rates at all intervals). Limitations included retrospective design, assessment variability, lack of pharmacokinetic data, and absence of baseline characteristics for long-term patients. Conclusions Prolonged sunitinib was not associated with new types or increased severity of TRAEs. Except hypothyroidism, toxicity was not cumulative. Patient summary More than 800 mRCC patients received sunitinib for between 2 and 6 yr without experiencing new or more severe treatment-related toxicity. Clinicians may be able to prescribe chronic sunitinib treatment for as long as patients continue to derive clinical benefit, without untoward additional risk

First-line treatment of metastatic clear cell renal cell carcinoma: a decision-making analysis among experts

Background: The treatment landscape of metastatic clear cell renal cell carcinoma (mccRCC) has been transformed by targeted therapies with tyrosine kinase inhibitors (TKI) and more recently by the incorporation of immune checkpoint inhibitors (ICI). Today, a spectrum of single agent TKI to TKI/ICI and ICI/ICI combinations can be considered and the choice of the best regimen is complex. Materials and methods: We performed an updated decision-making analysis among 11 international kidney cancer experts. Each expert provided their treatment strategy and relevant decision criteria in the first line treatment of mccRCC. After the collection of all input a list of unified decision criteria was determined and compatible decision trees were created. We used a methodology based on diagnostic nodes, which allows for an automated cross-comparison of decision trees, to determine the most common treatment recommendations as well as deviations. Results: Diverse parameters were considered relevant for treatment selection, various drugs and drug combinations were recommended by the experts. The parameters, chosen by the experts, were performance status, International Metastatic renal cell carcinoma Database Consortium (IMDC) risk group, PD-L1 status, zugzwang and contraindication to immunotherapy. The systemic therapies selected for first line treatment were sunitinib, pazopanib, tivozanib, cabozantinib, ipilimumab/nivolumab or pembrolizumab/axitinib. Conclusion: A wide spectrum of treatment recommendations based on multiple decision criteria was demonstrated. Significant inter-expert variations were observed. This demonstrates how data from randomized trials are implemented differently when transferred into daily practice

First-line bevacizumab combined with reduced dose interferon-α2a is active in patients with metastatic renal cell carcinoma

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Challenges and opportunities for converting renal cell carcinoma into a chronic disease with targeted therapies

Optimum efficacy is the primary goal for any cancer therapy, and entails controlling tumour growth and prolonging survival as far as possible. The prognosis for patients with metastatic renal cell carcinoma (mRCC) has greatly improved with the introduction of targeted therapies. This review examines the development and efficacy of targeted agents for the management of mRCC, the challenges offered by their rapid emergence, and discusses how mRCC treatment may evolve in the future. Improvements in progression-free survival and overall survival rates, observed with targeted agents, indicate that it may now be possible to change mRCC from a rapidly fatal and largely untreatable condition into a chronic disease. The major challenges to further advances in targeted therapy for mRCC include overcoming drug resistance, identifying the most effective sequence or combination of targeted agents, optimising clinical trial design and managing the cost of treatment

A phase I/II trial of sorafenib and infliximab in advanced renal cell carcinoma

There is clinical evidence to suggest that tumour necrosis factor-α (TNF-α) may be a therapeutic target in renal cell carcinoma (RCC). Multi-targeted kinase inhibitors, such as sorafenib and sunitinib, have become standard of care in advanced RCC. The anti-TNF-α monoclonal antibody infliximab and sorafenib have differing cellular mechanisms of action. We conducted a phase I/II trial to determine the safety and efficacy of infliximab in combination with sorafenib in patients with advanced RCC

Outcomes in Patients With Metastatic Renal Cell Carcinoma Who Develop Everolimus-Related Hyperglycemia and Hypercholesterolemia: Combined Subgroup Analyses of the RECORD-1 and REACT Trials

In this study we examined the outcome of metastatic renal cell cancer patients with everolimus treatment-related hyperglycemia and hypercholesterolemia. All patients were treated in 2 large, international prospective trials, RECORD-1 (REnal Cell cancer treatment with Oral RAD001 given Daily) and REACT (RAD001 Expanded Access Clinical Trial in RCC). Patients who experienced these events might have experienced an improved response to everolimus. Background Hyperglycemia and hypercholesterolemia are class effects of mammalian target of rapamycin inhibitors. The purpose of this study was to characterize safety and efficacy of patients with metastatic renal cell carcinoma (mRCC) treated with everolimus in RECORD-1 (REnal Cell cancer treatment with Oral RAD001 given Daily) and REACT (RAD001 Expanded Access Clinical Trial in RCC) who developed these events. Patients and Methods Adults with vascular endothelial growth factor–refractory mRCC received everolimus 10 mg/d in the randomized RECORD-1 (n = 277) and open-label REACT (n = 1367) studies. Outcomes included safety, treatment duration, overall response, and progression-free survival for patients who developed hypercholesterolemia or hyperglycemia. Results In RECORD-1, 12% (33 of 277) and 20% (55 of 277) of patients developed any grade hyperglycemia or hypercholesterolemia, respectively, with only 6% (78 of 1367) and 1% (14 of 1367) of the same events, respectively, in REACT. Median everolimus treatment duration was similar for patients with hyperglycemia or hypercholesterolemia (RECORD-1, 6.2 and 6.2 months, respectively; REACT, 4.4 and 4.5 months, respectively), but longer than the overall populations (RECORD-1, 4.6 months; REACT, 3.2 months). In RECORD-1/REACT, 82%/68% of patients with hyperglycemia and 75%/71% of patients with hypercholesterolemia achieved partial response or stable disease. The incidence of clinically notable Grade 3 or 4 adverse events, other than anemia and lymphopenia, appeared to be similar across trials and subgroups. Although there was a trend for improved progression-free survival with development of hyperglycemia or hypercholesterolemia, the association was not statistically significant. Conclusion Hyperglycemia and hypercholesterolemia were observed in low numbers of patients, and although these events might be associated with improved response to everolimus, the differences were not significant. These findings should be validated with prospective biomarker studies