Critical appraisal of bevacizumab in the treatment of metastatic colorectal cancer

Colorectal cancer is one of the most common cancers worldwide. The prognosis of patients with metastatic colorectal cancer in recent years has increased from 5 months with best supportive care to nearly 2 years with chemotherapy combined with bevacizumab, an antivascular endothelial growth factor monoclonal antibody. New prognostic and predictive biomarkers have been identified to guide chemotherapy in metastatic colorectal cancer, such as KRAS and BRAF oncogenes. However, the status of these oncogenes does not affect the efficacy of bevacizumab, and biomarkers predicting response to treatment with bevacizumab are still lacking. Addition of bevacizumab to regimens based on fluoropyrimidines or irinotecan has been shown to improve overall survival in treatment-naïve patients with metastatic colorectal cancer. Similarly, a significant increase in overall survival rate is achieved by adding bevacizumab to fluoropyrimidines and oxaliplatin in patients with disease progression. Bevacizumab has been found to be effective even when used as third-line therapy and later. In addition, cohort studies have shown that bevacizumab improves survival significantly despite disease progression. Finally, bevacizumab therapy in the neoadjuvant setting for the treatment of liver metastasis is well tolerated, safe, and effective.

Efficacy, safety, and cost-effectiveness (CE) analysis of pegfilgrastim (P) and lenograstim (L) in patients (pts) with nonmetastatic breast cancer (nmBC) receiving myelosuppressive chemotherapy (mCT)

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Background: Neutropenia (N) is common in pts who receive mCT. This retrospective study was conducted to determine efficacy, safety and cost of single injection of P (6 mg) compared with daily L (263 μg), in primary prophilaxis of N in pts affected by nmBC, who received mCT. Methods: 50 women (median age 54 years) underwent to median 6 (range 4–8) CT doses with antracyclines +/- taxanes. At every cycle, 28 pts received daily L (median 5 injections from day 5 to 9), while 22 pts received one dose of P on day 2. Absolute neutrophil count, incidence of G3/G4-N, bone pain (BP: Numerical Rate Scale >7) and CE analysis were evaluated. Results: In overall population (OP) incidence of G3-N and G4-N was 25% and 68%, respectively in L vs 22.7% and 41%, respectively in P; two cases (7%) of febrile N (FN) occurred in pts treated with L and three cases (13.6%) of FN in P. In 19 pts treated with FEC100 (10 pts L vs 9 pts P) we observed 0% of G3-N and 30% of G4-N in L while 33% of G3-N and 44% of G4-N in P. 31 pts received TAC/AC+T (18 pts L vs 13 pts P) with G3-N and G4-N 38.8% and 66.6%, respectively in L vs 15.3% and 30.7%, respectively in P. 18.2% of pts, who received P, had BP vs 35.7% in L. Reduction of CT doses was observed in 35.7% in L vs 41% in P. In Italy the cost of 1 injection of P was about 1489,00 euro compared with about 655,00 euro for 5 injections of L. Conclusions: In our experience, 1 injection of P was more effective and expensive than 5 daily administration of L to control N in OP and in particular in TAC/AC+T, while in FEC100, L was satisfactory with good CE profile. No difference about incidence of NF. Safety of P and L were similar with a lower incidence of BP in P.

Nonpegylated liposomal doxorubicin (nPLD) in neoadjuvant treatment of local advanced breast cancer (LABC) patients (pts)

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Background: Anthracycline is very effective in treatment of breast cancer, however it can cause cardiac toxicity events. nPLD has greater safety profile and comparable efficacy than conventional anthracyclines. We evaluated safety and efficacy, in neoadjuvant setting, of nPLD in pts with LABC. Methods: 11 pts (median age 57 years). Their clinical stage was: stages IIA and IIB 1 pt respectively, IIIB 7 pts, IIIC 2 pts. 8 pts presented at diagnosis with cT4 disease. All pts were treated with nPLD (50 mg/mq, d1q21) plus Docetaxel (75 mg/mq, d1q21) and Cyclophosphamide (500 mg/mq, d1q21); only 1 pt received Cyclophosphamide, nPLD and Trastuzumab. At beginning of therapy, overall population had left ventricular ejection fraction (LVEF) ≥55%. Results: After a median of 4 chemotherapy cycles, we observed following clinical response: stable disease 2 pts (18%); partial response 7 pts (64%); complete response 2 pts (18%). 9 pts were evaluable for radiological response: objective response rate and clinical benefit were 78 % and 100% respectively. 8 pts underwent surgery, in 3 pts was performed breast-conserving surgery. At the definitive histological examination pathologic stage was: IA 4 pts (50%), IIIA 1 pts (12,5%), IIIB 2 pts (25%) and IIIC 1 pts (12,5%). 2 pts experienced cardiac toxicity: 1 pt had an atrial fibrillation G2 while 1 pt had an symptomatic decline of LVEF G3 after first cycle, causing interruption of treatment. Other pts not showed clinically significant reduction of LVEF (>5%). Conclusions: Despite small number of pts, our experience suggests a safety profile and efficacy of nPLD in neoadjuvant settings for LABC; breast conservation was possible in 3 pts, in other pts (73%) this was not possible mainly for the advanced stage (T4).

“Long extended” temozolomide in a selected population with not radically resected high-grade gliomas

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Background: Despite the important progress in the treatment of solid tumors, high grade gliomas (HGGs) remain neoplasm with poor prognosis, especially when are not radically resected. Here we report the results of a selected population treated with standard schedule of Radiotherapy (RT) + Temozolomide (TMZ) followed by TMZ until progression. Methods: From January 2008 to January 2010, 14 newly diagnosed HGG patients, with median age of 50.6 years (range 27-75 yrs), were enrolled at Oncology Unit of S. Maria Goretti Hospital in Latina (University of Rome “Sapienza”). All patients were not radically resected and with ECOG PS=O. Furthermore patients were selected according to O6 Methyl-Guanine-DNA-Methyl Transferase (MGMT) promoter methylation status. Only methylated patients were included in our study. After surgery, patients received standard treatment with TMZ (75 mg/m2) concomitant with RT (60 Gy total dose). After a break of six weeks, Magnetic Resonance Imaging (MRI) was performed and all patients with stable or responsive disease received TMZ (150mg/200mg/m2/d x 5dq 28d) until progression. The response to treatment was evaluated according to RANO criteria Results: In our study the results showed one year overall survival (OS) and progression free survival (PFS) rates of 85,7% and 71,4% respectively. Moreover we observed two years OS rate of 70% and two years PFS rate of 10%. A total of 108 cycles of adjuvant TMZ were administered with average number of 9 per patient (range 1-16). The most frequent side effects observed were haematological toxicity and fatigue. Thrombocytopenia (G2-G3) was observed in 42% of patients, neutropenia (G2-G3), fatigue (G2-G3) and nausea (G2-G3) in 30%, 32% and 25% of patients respectively. Conclusions: Despite the small number of patients, our experience suggests a manageable safety profile and a good efficacy of TMZ until progression in a selected population of patients (HGGs not radically resected, with a good ECOG PS). These data also confirms the literature knowledge, underlining the prognostic positive impact of MGMT promoter methylation in patients with HGG.

Incidence of chemotherapy (CT)-induced amenorrhea in premenopausal patients (pts) with breast cancer (BC) following adjuvant anthracycline (A), cyclophosphamide (C), and taxane (T)

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Background: CT may induce amenorrhea or menopause to a variable extent. These side-effects may impair or impede fertility, cause sexual dysfunction, bone loss and menopausal symptoms in many women. We analyzed incidence of amenorrhea in premenopausal pts affected by BC treated with CT. Methods: In this retrospective study we evaluated the incidence of amenorrhea in 24 premenopausal BC pts (43 median age years) treated with adjuvant A + C +/- T based CT. Overall population (OP) had regular menstrual cycle and no pts began hormone therapy, at the same time. Results: 10 pts (42%) received only A + C, 6 pts (25%) received A + C + T, 8 pts (33%) received A + C and after T. In 22 pts (92%) amenorrhea appeared during CT; in particular, 9/10 pts (90%) treated with A + C , 5/6 pts (83%) with A + C + T and 8/8 pts (100%) with A + C and after T. In OP amenorrhea appeared during first three cycles of CT in 18 pts (82%) and particularly 7 pts (32%) after 1 cycle, 7 pts (32%) after 2 cycles, 4 pts (18%) after 3 cycles and 4 pts (18%) in subsequent doses. Amenorrhea occurred within the first two doses of treatment in 14/22 pts (64%); in 6/9 pts (66.7%) treated with A + C, in 4/5 pts (80%) with A + C + T and in 4/8 (50%) with A + C and after T. In 7 pts (32%), median age 40 years, at the end of CT reappeared menstrual cycle. Conclusions: In our small experience the incidence of amenorrhea during CT was extremely high and there are no differences between subgroups undergoing to CT with A + C alone or combined with T. In the group of pts in which T were given concomitant with A and C, amenorrhea occurred earlier than the other two groups. Menstrual cycle reappeared at the end of CT in younger pts.

Ultrasoft colloid-polymer mixtures: structure and phase diagram

Binary mixtures of ultrasoft colloids and linear polymer chains were investigated by small-angle neutron scattering and liquid state theory. We show that experimental data can be described by employing recently developed effective interactions between the colloid and the polymer chains, in which both components are modeled as point particles in a coarse-grained approach, in which the monomers have been traced out. Quantitative, parameter-free agreement between experiment and theory for the pair correlations, the phase behavior and the concentration dependence of the interaction length is achieved.

Crystallization and aging in hard-sphere glasses

We report new results from our programme of molecular dynamics simulation of hard-sphere systems, focusing on crystallization and glass formation at high concentrations. First we consider a much larger system than hitherto, N = 86 400 equal-sized particles. The results are similar to those obtained with a smaller system, studied previously, showing conventional nucleation and growth of crystals at concentrations near melting and crossing over to a spinodal-like regime at higher concentrations where the free energy barrier to nucleation appears to be negligible. Second, we investigate the dependence on the initial state of the system. We have devised a Monte Carlo 'constrained aging' method to move the particles in such a way that crystallization is discouraged. After a period of such aging, the standard molecular dynamics programme is run. For a system of N = 3200, we find that constrained aging encourages caging of the particles and slows crystallization somewhat. Nevertheless, both aged and unaged systems crystallize at volume fraction φ = 0.61 whereas neither system shows full crystallization in the duration of the simulation at φ = 0.62, a concentration still significantly below that of random close packing.

Competing interactions in arrested States of colloidal clays

Using experiments, theory and simulations, we show that the arrested state observed in a colloidal clay at high concentrations is stabilized by screened Coulomb repulsion (Wigner glass). Dilution experiments allow us to distinguish this disconnected state, which melts upon addition of water, from a low-concentration gel state, which does not melt. Theoretical modeling and simulations at high concentrations reproduce the measured small angle x-ray scattering static structure factors and confirm the long-range electrostatic nature of the arrested structure. These findings are attributed to the different time scales controlling the competing attractive and repulsive interactions.

Hard spheres: crystallization and glass formation

Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s>0.07. For 0.02<s<0.07, we find that increasing the polydispersity at a given concentration slows down crystal nucleation. The main effect here is that polydispersity reduces the supersaturation since it tends to stabilize the fluid but to destabilize the crystal. At a given polydispersity (<0.07), we find three regimes of nucleation: standard nucleation and growth at concentrations in and slightly above the coexistence region; 'spinodal nucleation', where the free-energy barrier to nucleation appears to be negligible, at intermediate concentrations; and, at the highest concentrations, a new mechanism, still to be fully understood, which only requires small rearrangement of the particle positions. The cross-over between the second and third regimes occurs at a concentration, approximately 58 per cent by volume, where the colloid experiments show a marked change in the nature of the crystals formed and the particle dynamics indicate an 'ideal' glass transition.

Crystallization of hard-sphere glasses

We study by molecular dynamics the interplay between arrest and crystallization in hard spheres. For state points in the plane of volume fraction (0.54 <or= varphi <or= 0.63) and polydispersity (0 <or= s <or= 0.085), we delineate states that spontaneously crystallize from those that do not. For noncrystallizing (or precrystallization) samples we find isodiffusivity lines consistent with an ideal glass transition at varphi_{g} approximately 0.585, independent of s. Despite this, for s < 0.05, crystallization occurs at varphi > varphi_{g}. This happens on time scales for which the system is aging, and a diffusive regime in the mean square displacement is not reached; by those criteria, the system is a glass. Hence, contrary to a widespread assumption in the colloid literature, the occurrence of spontaneous crystallization within a bulk amorphous state does not prove that this state was an ergodic fluid rather than a glass.

Asymmetric caging in soft colloidal mixtures

The long-standing observations that different amorphous materials exhibit a pronounced enhancement of viscosity and eventually vitrify on compression or cooling continue to fascinate and challenge scientists, on the ground of their physical origin and practical implications. Glass formation is a generic phenomenon, observed in physically quite distinct systems that encompass hard and soft particles. It is believed that a common underlying scenario, namely cage formation, drives dynamical arrest, especially at high concentrations. Here, we identify a novel, asymmetric glassy state in soft colloidal mixtures, which is characterized by strongly anisotropically distorted cages, bearing similarities to those of hard-sphere glasses under shear. The anisotropy is induced by the presence of soft additives. This phenomenon seems to be generic to soft colloids and its origins lie in the penetrability of the constituent particles. The resulting phase diagram for mixtures of soft particles is clearly distinct from that of hard-sphere mixtures and brings forward a rich variety of vitrified states that delineate an ergodic lake in the parameter space spanned by the size ratio between the two components and by the concentration of the additives. Thus, a new route opens for the rational design of soft particles with desired tunable rheological properties.

Asymmetric poly(ethylene-alt-propylene)-poly(ethylene oxide) micelles: a system with starlike morphology and interactions

We report on an experimental study of single particle properties and interactions of poly(ethylene-alt-propylene)-poly(ethylene oxide) (PEP-PEO) starlike micelles. The starlike regime is achieved by an extremely asymmetric block ratio (1:20) and the number of arms (functionality) is changed by varying the composition of the solvent (the interfacial tension). Small angle neutron scattering (SANS) data in the dilute regime can be modeled by assuming a constant density profile in the micellar core (compact core) and a starlike density profile in the corona (starlike shell). The starlike morphology of the corona is confirmed by a direct comparison with SANS measurements of dilute poly butadiene star solutions. Comparison of structure factors obtained by SANS measurements in the concentrated regime shows in addition that the interactions in the two systems are equivalent. Micellar structure factors at several packing fractions can be modeled by using the ultrasoft potential recently proposed for star polymers [Likos, Phys. Rev. Lett. 80, 4450 (1998)]. The experimental phase diagram of PEP-PEO micelles is quantitatively compared to theoretical expectations, finding good agreement for the location of the liquid-solid boundary and excellent agreement for the critical packing fraction where the liquid-to-bcc crystal transition takes place for f<70. The functionality, i.e., the coronal density, strongly influences the nature of the solid phase: for f<70 the system crystallizes into a bcc phase, high f>70 formation of amorphous arrested states prevents crystallization.

Non-Gaussian energy landscape of a simple model for strong network-forming liquids: Accurate evaluation of the configurational entropy

We present a numerical study of the statistical properties of the potential energy landscape of a simple model for strong network-forming liquids. The model is a system of spherical particles interacting through a square-well potential, with an additional constraint that limits the maximum number of bonds Nmax per particle. Extensive simulations have been carried out as a function of temperature, packing fraction, and Nmax. The dynamics of this model are characterized by Arrhenius temperature dependence of the transport coefficients and by nearly exponential relaxation of dynamic correlators, i.e., features defining strong glass-forming liquids. This model has two important features: (i) Landscape basins can be associated with bonding patterns. (ii) The configurational volume of the basin can be evaluated in a formally exact way, and numerically with an arbitrary precision. These features allow us to evaluate the number of different topologies the bonding pattern can adopt. We find that the number of fully bonded configurations, i.e., configurations in which all particles are bonded to Nmax neighbors, is extensive, suggesting that the configurational entropy of the low temperature fluid is finite. We also evaluate the energy dependence of the configurational entropy close to the fully bonded state and show that it follows a logarithmic functional form, different from the quadratic dependence characterizing fragile liquids. We suggest that the presence of a discrete energy scale, provided by the particle bonds, and the intrinsic degeneracy of fully bonded disordered networks differentiates strong from fragile behavior.

Gel to glass transition in simulation of a valence-limited colloidal system

We numerically study a simple model for thermoreversible colloidal gelation in which particles can form reversible bonds with a predefined maximum number of neighbors. We focus on three and four maximally coordinated particles, since in these two cases the low valency makes it possible to probe, in equilibrium, slow dynamics down to very low temperatures T. By studying a large region of T and packing fraction phi we are able to estimate both the location of the liquid-gas phase separation spinodal and the locus of dynamic arrest, where the system is trapped in a disordered nonergodic state. We find that there are two distinct arrest lines for the system: a glass line at high packing fraction, and a gel line at low phi and T. The former is rather vertical (phi controlled), while the latter is rather horizontal (T controlled) in the phi-T plane. Dynamics on approaching the glass line along isotherms exhibit a power-law dependence on phi, while dynamics along isochores follow an activated (Arrhenius) dependence. The gel has clearly distinct properties from those of both a repulsive and an attractive glass. A gel to glass crossover occurs in a fairly narrow range in phi along low-T isotherms, seen most strikingly in the behavior of the nonergodicity factor. Interestingly, we detect the presence of anomalous dynamics, such as subdiffusive behavior for the mean squared displacement and logarithmic decay for the density correlation functions in the region where the gel dynamics interferes with the glass dynamics.

Tailoring the flow of soft glasses by soft additives

We examine the vitrification and melting of asymmetric star polymer mixtures by combining rheological measurements with mode coupling theory. We identify two types of glassy states, a single glass, in which the small component is fluid in the glassy matrix of the big one, and a double glass, in which both components are vitrified. Addition of small-star polymers leads to melting of both glasses, and the melting curve has a nonmonotonic dependence on the star-star size ratio. The phenomenon opens new ways for externally steering the rheological behavior of soft matter systems.

One-Dimensional Cluster Growth and Branching Gels in Colloidal Systems with Short-Range Depletion Attraction and Screened Electrostatic Repulsion

We report extensive numerical simulations of a simple model for charged colloidal particles in suspension with small nonadsorbing polymers. The chosen effective one-component interaction potential is composed of a short-range attractive part complemented by a Yukawa repulsive tail. We focus on the case where the screening length is comparable to the particle radius. Under these conditions, at low temperature, particles locally cluster into quasi one-dimensional aggregates which, via a branching mechanism, form a macroscopic percolating gel structure. We discuss gel formation and contrast it with the case of longer screening lengths, for which previous studies have shown that arrest is driven by the approach to a Yukawa glass of spherical clusters. We compare our results with recent experimental work on charged colloidal suspensions (Phys. Rev. Lett. 2005, 94, 208301).

Energy landscape of a simple model for strong liquids

We calculate the statistical properties of the energy landscape of a minimal model for strong network-forming liquids. Dynamic and thermodynamic properties of this model can be computed with arbitrary precision even at low temperatures. A degenerate disordered ground state and logarithmic statistics for the local minima energy distribution are the landscape signatures of strong liquid behavior. Differences from fragile liquid properties are attributed to the presence of a discrete energy scale, provided by the particle bonds, and to the intrinsic degeneracy of topologically disordered networks.

Model for reversible colloidal gelation

We report a numerical study, covering a wide range of packing fraction Phi and temperature T, for a system of particles interacting via a square well potential supplemented by an additional constraint on the maximum number n(max) of bonded interactions. We show that, when n(max)<6, the liquid-gas coexistence region shrinks, giving access to regions of low Phi where dynamics can be followed down to low T without an intervening phase separation. We characterize these arrested states at low densities (gel states) in terms of structure and dynamical slowing down, pointing out features which are very different from the standard glassy states observed at high Phi values.

Starlike micelles with starlike interactions: a quantitative evaluation of structure factors and phase diagram

Starlike PEP-PEO block copolymer micelles offer the possibility to investigate the phase behavior and interactions of regular star polymers (ultrasoft colloids). Micellar functionality f can be smoothly varied by changing solvent composition (interfacial tension). Structure factors obtained by small-angle neutron-scattering can be quantitatively described in terms of an effective potential for star polymers. The experimental phase diagram reproduces to a high level of accuracy the predicted liquid-solid transition. Whereas for intermediate f a bcc phase is observed, for high f the formation of a fcc phase is preempted by glass formation.

Ground-state clusters for short-range attractive and long-range repulsive potentials

We report calculations of the ground-state energies and geometries for clusters of different sizes (up to 80 particles), where individual particles interact simultaneously via a short-ranged attractive potential, modeled with a generalization of the Lennard-Jones potential, and a long-ranged repulsive Yukawa potential. We show that for specific choices of the parameters of the repulsive potential, the ground-state energy per particle has a minimum at a finite cluster size. For these values of the parameters in the thermodynamic limit, at low temperatures and small packing fractions, where clustering is favored and cluster-cluster interactions can be neglected, thermodynamically stable cluster phases can be formed. The analysis of the ground-state geometries shows that the spherical shape is marginally stable. In the majority of the studied cases, we find that above a certain size, ground-state clusters preferentially grow almost in one dimension.

Effect of bond lifetime on the dynamics of a short-range attractive colloidal system

We perform molecular dynamics simulations of short-range attractive colloid particles modeled by a narrow (3% of the hard sphere diameter) square well potential of unit depth. We compare the dynamics of systems with the same thermodynamics but different bond lifetimes, by adding to the square well potential a thin barrier at the edge of the attractive well. For permanent bonds, the relaxation time tau diverges as the packing fraction phi approaches a threshold related to percolation, while for short-lived bonds, the phi dependence of tau is more typical of a glassy system. At intermediate bond lifetimes, the phi dependence of tau is driven by percolation at low phi , but then crosses over to glassy behavior at higher phi . We also study the wave vector dependence of the percolation dynamics.