Transient phenomena in thixotropic systems Mujumdar, Ashutosh; Beris, Antony N.; Metzner, Arthur B.
Journal of non-Newtonian fluid mechanics,
02/2002, Letnik:
102, Številka:
2
Journal Article
Recenzirano
A nonlinear rheological model which accounts for the time-dependent elastic, viscous and yielding phenomena is developed in order to describe the flow behavior of thixotropic materials which exhibit ...yield stress. A key feature of the formulation is a smooth transition from an ‘elastically’ dominated response to a ‘viscous’ response without a discontinuity in the stress–strain curve. The model is phenomenological and is based on the kinetic processes responsible for structural changes within the thixotropic material. As such, it can predict thixotropic effects, such as stress overshoot during start-up of a steady shear flow and stress relaxation after cessation of flow. Thus this model extends a previously proposed viscoplastic model J. Rheol. 34 (1991) 647 to include thixotropy.
An analysis and comparison to experimental data involving oscillatory shear flow are provided to evaluate the accuracy of the model and to estimate the model parameters in a prototype concentrated suspension. The experiments were conducted using a series of concentrated suspensions of silicon particles and silicon carbide whiskers in polyethylene. The data obtained with this experimental system indicated much better agreement between the theory and experiments that obtained in earlier work.
We report the 12-year follow-up of the prospective randomized EBMT LYM1 trial to determine whether the benefit of brief duration rituximab maintenance (RM) on progression-free survival (PFS) in ...patients with relapsed follicular lymphoma (FL) receiving an autologous stem cell transplant (ASCT) is sustained. One hundred and thirty-eight patients received RM with or without purging. The median follow-up after random assignment is 12 years (range 10-13) for the whole series. The 10-year PFS after ASCT is 47% (95% CI 40-54) with only 4 patients relapsing after 7.5 years. RM continues to significantly improve 10-year PFS after ASCT in comparison with NM P = 0.002; HR 0.548 (95% CI 0.38-0.80). Ten-year non-relapse mortality (NRM) was not significantly different between treatment groups (7% overall). 10-year overall survival (OS) after ASCT was 75% (69-81) for the whole series, with no significant differences according to treatment sub-groups. 10-year OS for patients who progressed within 24 months (POD24T) was 60%, in comparison with 85% for patients without progression. Thus the benefit of rituximab maintenance after ASCT on relapse prevention is sustained at 12 years, suggesting that RM adds to ASCT-mediated disease eradication and may enhance the curative potential of ASCT.
Metabolic syndrome (MetS) is associated with cardiovascular disease in the general population and is also a potential cardiovascular risk factor in survivors of haematopoietic cell transplantation ...(HCT). We report an EBMT cross-sectional, multi-centre, non-interventional study of 453 adult HCT patients surviving a minimum of 2 years post-transplant attending routine follow-up HCT and/or late effects clinics in 9 centres. The overall prevalence of MetS was 37.5% rising to 53% in patients >50 years of age at follow-up. There were no differences in rates of MetS between autologous and allogeneic HCT survivors, nor any association with graft-versus-host disease (GvHD) or current immunosuppressant therapy. Notably, there was a significantly higher occurrence of cardiovascular events (CVE, defined as cerebrovascular accident, coronary heart disease or peripheral vascular disease) in those with MetS than in those without MetS (26.7% versus 9%, p < 0.001, OR 3.69, 95% CI 2.09-6.54, p < 0.001), and, as expected, MetS and CVE were age-related. Unexpectedly, CVE were associated with occurrence of second malignancy. Screening for and management of MetS should be integrated within routine HCT long-term follow-up care for both allogeneic and autologous HCT survivors. Further research is warranted, including randomised controlled trials of interventional strategies and mechanistic studies of cardiovascular risk in HCT survivors.
We conducted a prospectively randomized clinical trial to compare the efficacy of three outpatient therapy regimens in 341 patients with progressive metastatic renal cell carcinoma.
Patients were ...stratified according to known clinical predictors and were subsequently randomly assigned. Treatment arms were: arm A (n = 132), subcutaneous interferon alfa-2a (sc-IFN-alpha-2a), subcutaneous interleukin-2 (sc-IL-2), and intravenous (IV) fluorouracil; arm B (n = 146): arm A treatment combined with per oral 13-cis-retinoic acid; and arm C (n = 63), sc-IFN-alpha-2a and IV vinblastine.
Treatment (according to the standard 8-week Hannover Atzpodien regimen) arms A, B, and C yielded objective response rates of 31%, 26%, and 20%, respectively. Arm B, but not arm A, showed a significantly improved progression-free survival (PFS) compared with arm C (P =.0248). Both arm A (median overall survival, 25 months; P =.0440) and arm B (median overall survival, 27 months; P =.0227) led to significantly improved overall survival (OS) compared with arm C (median OS, 16 months). All three sc-IFN-alpha-2a-based therapies were moderately or well tolerated.
Our results established the safety and improved long-term therapeutic efficacy of sc-IL-2 plus sc-INF-alpha-2a-based outpatient immunochemotherapies, compared with sc-INF-alpha-2a/IV vinblastine.
Current guidelines recommend consolidation with autologous stem cell transplantation (autoSCT) after induction chemotherapy for most patients with peripheral T-cell lymphoma (PTCL). This assumption ...is based on five prospective phase II studies, three of which included <50 patients with limited follow-up. Here we present the final analysis of the prospective German study. The treatment regimen consisted of four to six cycles of CHOP chemotherapy followed by mobilizing therapy and stem cell collection. Patients in complete remission (CR) or partial remission (PR) underwent myeloablative chemo(radio)therapy and autoSCT. From January 2001 to July 2010, 111 patients were enrolled in the study. The main subgroups were PTCL not specified (n=42) and angioimmunoblastic T-cell lymphoma (n=37). Seventy-five (68%) of the 111 patients received transplantation. The main reason for not receiving autoSCT was progressive disease. In an intent-to-treat analysis, the complete response rate after myeloablative therapy was 59%. The estimated 5-year overall survival, disease-free survival and progression-free survival rates were 44%, 54% and 39%, respectively. The results of this study confirm that upfront autoSCT can result in long-term remissions in patients with all major subtypes of PTCL and therefore should be part of first-line therapy whenever possible.
Lymphoplasmacytic lymphoma (LPL) is an indolent lymphoma with moderate sensitivity to conventional chemotherapy. This study investigated whether the addition of rituximab to standard chemotherapy ...improves treatment outcome in LPL and the subgroup of LPL patients fulfilling the criteria of Waldenstroem's macroglobulinemia (WM). A total of 69 patients with previously untreated LPL were enrolled into the trial; 64 patients were evaluable for treatment outcome. In all, 48 of the 64 LPL patients fulfilled the criteria of WM. Patients were randomly assigned to R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone, n=34) or CHOP (n=30). R-CHOP resulted in significantly higher overall response (OR) rate (94 vs 67%, P=0.0085) in the LPL patients and in the WM subgroup (91 vs 60%, P=0.0188). With a median observation time of 42 months, R-CHOP induced a significantly longer time to treatment failure (TTF) with a median of 63 months for R-CHOP vs 22 months in the CHOP arm in the LPL patients (P=0.0033) and in the WM subgroup (P=0.0241). There was no major difference of treatment-associated toxicity between both treatment groups. These data indicate that the addition of rituximab to front-line chemotherapy improves treatment outcome in patients with LPL or WM.
Background: Studies on cognitive functioning in breast cancer patients point out that a subset of women exhibit chemotherapy-related neuropsychological impairment. Thereby, high-dose therapy may ...elevate the risk of cognitive dysfunctions. The primary purpose of the study was to evaluate the impact of high-dose versus standard-dose chemotherapy on the late neuropsychological outcome in randomized assigned high-risk breast cancer survivors. Next to focusing prevalence, function specificity and extent of cognitive impairment, the question as to whether doses-dependant group differences occur was investigated. Patients and methods: Twenty-four high-dose and 23 standard-dose patients 5 years, on average, after treatment underwent a comprehensive neuropsychological assessment. In addition, 29 early-stage breast cancer patients matched for age, education and time since treatment were recruited as a comparison group. Results: Global cognitive impairment was observed in 8% of high-dose versus 13% of standard-dose compared with 3% of early-stage breast cancer patients. Compared with normative data, all patient groups performed worse on one attention subtest measuring the simple reaction time (P < 0.001 in each case). By contrast, no significant between-group differences on the late neuropsychological outcome were found. Conclusions: Five years after treatment, standard-dose patients were slightly, but not significantly, more impaired in cognitive performance than high-dose patients.
Long-term survival is rarely achieved in patients with cisplatin-refractory germ cell cancer (GCT). Both single-agent gemcitabine and oxaliplatin have shown activity in patients who experience ...relapse or are refractory to cisplatin treatment. This study investigates the activity of a gemcitabine plus oxaliplatin regimen in these patients.
Gemcitabine was administered at a dose of 1,000 mg/m(2) on days 1 and 8; oxaliplatin was administered at a dose of 130 mg/m(2) on day 1. Response was evaluated every 4 weeks.
Thirty-five patients with a median age of 37 years (range, 21 to 54 years) were enrolled onto the study. Primary tumor localization was gonadal, retroperitoneal, or mediastinal in 30, one, and four patients, respectively. Patients had been pretreated with a median of six platinum-containing cycles (range, four to 13 cycles) and 89% of patients previously had experienced treatment failure after high-dose chemotherapy with peripheral-blood stem-cell transplantation. Sixty-three percent of patients were considered absolutely cisplatin-refractory or cisplatin-refractory. A median of two cycles (range, 1 to 6 cycles) per patient were applied. Toxicity consisted mainly of myelosuppression, with Common Toxicity Criteria grade 3 occurring in 54% of patients. Only 9% of patients developed neutropenic fever. Three patients attained a complete remission (CR), two patients attained a marker-negative partial remission, and 11 patients attained a marker-positive partial remission, resulting in an overall response rate of 46% (95% CI, 30% to 64%). All three patients with CR and one patient with a marker-negative partial remission remained disease free at 16+, 12+, 4+, and 2+ months of follow-up. Seven (44%) of these 16 responses, including one CR, occurred in cisplatin-refractory patients.
Gemcitabine plus oxaliplatin demonstrates antitumor activity with acceptable toxicity in heavily pretreated patients with relapsed or cisplatin-refractory GCT, and may offer a chance of long-term survival for selected patients.
T-cell lymphomas (T-NHL) generally carry a poor prognosis. High-dose therapy (HDT) and autologous stem cell transplantation (ASCT) are increasingly used to treat younger patients.
We treated patients ...<61 years with high-risk aggressive lymphoma with four to six courses of dose-escalated CHOP plus etoposide (MegaCHOEP) necessitating repeated ASCT. Outcomes of patients with mature T-NHL (excluding anaplastic lymphoma kinase-positive anaplastic large cell lymphoma) and aggressive B-NHL were compared using multivariate Cox regression analysis.
Compared with 84.4% of B-NHL patients, 66.7% of T-NHL patients were able to receive all treatments; the rates of progressive disease were 27.3% in T-NHL and 16.3% in B-NHL patients. At 3 years, event-free survival (EFS) and overall survival were significantly worse for T-NHL 25.9% confidence interval (CI) 10.4% to 41.4% and 44.5% CI 26.5% to 62.5%) than for B-NHL patients (60.1% CI 52.1% to 68.1%; P < 0.001 and 63.4% CI 55.4% to 71.4%; P = 0.016). In multivariate analysis, T-NHL was a strongly significant adverse risk factor for EFS (relative risk 2.2, P=0.001).
MegaCHOEP for T-NHL patients was no better than other high-dose regimens and was unable to address the major problems of HDT/ASCT: neither early progressions nor early relapses were reduced. This study sheds some doubt on expectations that HDT/ASCT will significantly improve outcomes for patients with T-NHL.
PDF
