This article reports an experimental and theoretical study of the peroxide‐induced degradation of polypropylene in a corotating twin‐screw extruder. Experiments were performed with different peroxide concentrations and different operating conditions. The evolution of the chemical reaction along the extruder was monitored with specific sampling devices. Material changes were characterized by rheological measurements and via the determination of the molecular weights of samples collected at the same locations. The theoretical results were obtained with a model that coupled the interactions between flow conditions encountered in the extruder, the kinetics of the reaction, and the changes in the viscosity induced by changes in the molecular weight. The experimental results evidenced the relationships between the process conditions (peroxide concentration and processing parameters) and material properties (rheological properties and molecular structure of the modified polypropylene). Good agreement between the theoretical and experimental results was obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

BACKGROUND.The authors investigated whether stereotactic radiosurgery (SRS) alone improved outcomes for patients in recursive partitioning analysis (RPA) Classes 1 and 2 who had 1 to 3 brain metastases compared with whole‐brain radiotherapy (WBRT).METHODS.Data regarding 186 patients in RPA Classes 1 and 2 who had 1 to 3 brain metastases and who received either 30 to 40 grays (Gy) of WBRT (n = 91 patients) or 18 to 25 Gy SRS (n = 95 patients) were analyzed retrospectively. Eight other potential prognostic factors were evaluated regarding overall survival (OS), entire brain control (BC), local control (LC) of treated metastases, and brain control distant from treated metastases (distant control [DC]): Those 8 factors were age, sex, performance status, tumor type, number of brain metastases, extracranial metastases, RPA class, and interval from tumor diagnosis to radiotherapy.RESULTS.On multivariate analysis of OS, age ( risk ratio [RR], 1.51; P = .024), Karnofsky performance status (KPS) (RR, 1.98; P = .002), and extracranial metastases (RR, 2.26; P < .001) were significant, whereas the radiation regimen was not significant (P = .89). On multivariate analysis of BC, only the radiation regimen (RR, 1.33; P = .003) was found to be significant. On multivariate analysis of LC, radiation regimen (RR, 1.63; P < .001) and sex (RR, 1.62; P = .022) were significant. On multivariate analysis of DC, KPS (RR, 1.85; P = .049) and extracranial metastases (RR, 1.69; P = .047) were significant. The radiation regimen was not found to be significant even on univariate analysis (P = .80). In RPA class subgroup analyses, BC and LC were better after SRS than WBRT for patients in RPA Classes 1 and 2, whereas OS and DC did not differ significantly.CONCLUSIONS.For patients in RPA Classes 1 and 2 who had 1 to 3 brain metastases, SRS alone was associated with improved BC and LC compared with 30 to 40 Gy WBRT, whereas OS and DC were not significantly different. Similar results were observed in separate subgroup analyses of patients in RPA Class 1 and RPA Class 2. Cancer 2007. © 2007 American Cancer Society.

BACKGROUND. The current study was conducted to compare 2 treatment regimens including surgical resection and whole‐brain radiotherapy (WBRT) for patients with 1 to 2 brain metastases. METHODS. A total of 201 patients with recursive partitioning analysis (RPA) class 1 to 2 disease with 1 to 2 resectable brain metastases were analyzed retrospectively. Patients underwent either resection of the metastases plus WBRT with 10 fractions of 3 grays (Gy) each or 20 fractions of 2 Gy each (99 patients; Group A) or the same treatment plus a WBRT boost to the metastatic site (10 fractions of 3 Gy each plus 5 fractions of 3 Gy each or 20 fractions of 2 Gy each plus 5 fractions of 2 Gy each) (102 patients; Group B). Eight other potential prognostic factors were evaluated with regard to overall survival (OS), brain control (BC), and local control of resected metastases (LC): age, gender, Karnofsky performance status, extent of surgical resection, tumor type, extracranial metastases, RPA class, and interval from tumor diagnosis to WBRT. RESULTS. Group B patients had better 1‐year OS (66% vs 41%; P < .001). On multivariate analysis of OS, treatment regimen (relative risk [RR] of 1.94; P < .001), extent of surgical resection (RR of 1.80; P = .001), and interval from tumor diagnosis to WBRT (RR of 1.62; P = .010) were found to be statistically significant. On multivariate analysis of BC, treatment regimen (RR of 2.15; P = .002), extent of surgical resection (RR of 2.78; P < .001), and interval from tumor diagnosis to WBRT (RR of 1.52; P = .034) were found to be statistically significant. On multivariate analysis of LC, treatment regimen (RR of 2.31; P = .002) and extent of surgical resection (RR of 3.79; P < .001) were found to be statistically significant. On RPA class subgroup analyses, outcome was found to be significantly better with a WBRT boost in both RPA class 1 and class 2 patients. A WBRT boost resulted in better outcome after both complete and incomplete surgical resection. However, the results concerning BC and LC were not found to be statistically significant if surgical resection was incomplete. CONCLUSIONS. After surgical resection of 1 to 2 brain metastases, a boost of 10 to 15 Gy in addition to WBRT was found to improve outcome. After incomplete surgical resection, further dose escalation to the metastatic site may be considered. Cancer 2007. © 2007 American Cancer Society.

OP + WBRT + boost appeared to provide the best outcomes of the compared treatment regimens in elderly patients with one to two brain metastases. If surgery is not possible, SRS may be considered.

A boost in addition to WBI significantly improved LC but not OS following resection of a single brain metastasis.