Analysis Of Failure Patterns Research Articles

Mechanical behavior of seawater sea-sand recycled concrete columns confined by engineered cementitious composite under eccentric compression

Corrosion of steel reinforcement is a major concern when applying seawater sea-sand concrete (SSC). This paper presents a seawater sea-sand recycled aggregate concrete (SSRAC) column confined by engineered cementitious composite (ECC) or conventional natural aggregate concrete (NAC) shell and its mechanical behavior under eccentric compression. With the analysis of bearing capacity, deformation and failure pattern, the results show that the bearing capacity of NAC shell confined SSRAC columns is 0.90–1.18 times to that of SSRAC columns, while that of ECC shell confined SSRAC columns increases 76–85% with the load eccentricity ratio of 0.3, and 83–109% with the load eccentricity ratio of 0.6. When the ECC shell is adopted, the lateral deformability of columns increases 34–111% with the load eccentricity ratio of 0.6 compared with the case of SSRAC column. Moreover, both the cross-section layer-by-layer method and simplified method were used to determine the bearing capacity of columns.

Effect of All-Component Recycled GFRP on Physical-Mechanical Properties and Microstructures of Concrete

Large inventory and non-degradability made waste glass fiber reinforced plastics (GFRP) a heavy burden to environment. They are increasingly reclaimed through mechanical crushing and used as aggregate replacement in concrete. However, reuse of all-component recycled GFRP (rGFRP) was still limited due to the inconsistent influences of powder and fiber on cementitious materials. In this study, mortar and concrete with two different gradations of all-component rGFRP at 10 wt%, 20 wt% and 30 wt% were investigated with mechanical tests, ultrasonic pulse velocity inspection, Depth-of-Field optical microscopy, Scanning Electron Microscopy (SEM) and micro-CT. It revealed that the splitting strength of cement mortar was significantly increased while 10 wt% of rGFRP was added, whereas the compressive and flexural strength were barely affected. For concrete, the initial and final setting time were prolonged by the addition of 30 wt% rGFRP up to 93.8% and 124.3%, respectively. The mechanical strength of concrete increased with rGFRP content firstly, and then decreased, due to the reduced dispersity of rGFRP and compactness of mortar. When 10 wt% of rGFRP was added, the 28-day compressive, flexural and splitting strength of concrete were optimized to 25.8 MPa, 4.25 MPa and 3.02 MPa, respectively. The failure pattern analysis indicated that rGFRP can restrain crack propagation, reduce crack width and improve the integrity of fractured concrete. The results suggested the potential feasibility of rGFRP as fine aggregate replacement, and provided solid experimental references for practically reusing rGFRP in cementitious materials.

On the possibility of using damaged plasticity models in the assessment of structural response of gravity beams

Advent of concrete damaged plasticity material models has drastically improved the accuracy in predicting the structural response of concrete structural elements using finite element Analysis. However, exploration of the accuracy of this method in analysing complex concrete forms is scanty. Gravity Beams, a term coined in this investigation, are those beams in which gravity is used to design the topology of beam form conjointly with the novel manufacturing strategy ‘Fabric Formwork’. In this investigation these beam forms were numerically analysed using prevalent material and damage models. Numerical structural response was evaluated using these models and compared to experimental response. It was deduced from the comparative evaluation that numerical models closely predict the structural response of gravity beams. Moreover, dissimilarity analysis revealed that the diversion of the results was due the shape error between Modelled gravity beams, which were used for numerical analysis, and actual 3D scanned beams. It was deduced after analysis of experimental and numerical failure patterns that local imperfections also play a major role in the deviation in the numerical model. Furthermore, cross-sectional proportion ratio (CPR) was also introduced to give a numerical identity to gravity beams. This ratio was used to frame a parametric comparison of gravity beams and the corresponding structural response, to explore the parametric dependency.

Mechanical Fatigue Analysis of PEEK as Alternative to Zirconia for Definitive Hybrid Abutments Supporting All-Ceramic Crowns.

The aim of this study was to inspect the mechanical fatigue behavior of an implant-supported restorative system using polyether ether ketone (PEEK) and yttria partially stabilized zirconia polycrystals (YZ) as materials for customized definitive implant-supported hybrid abutments, supporting two types of all-ceramic restorations: translucent zirconia (TZ) and lithium disilicate (LD) monolithic crowns. Forty Morse taper implants were included in epoxy resin. Titanium intermediary abutments were placed, and the specimens were randomly allocated into four groups (n = 10) according to the customized hybrid abutment material (PEEK or YZ) and the monolithic crowns (TZ or LD) representing a maxillary central incisor crown. The specimens were subjected to a mechanical fatigue test (step-stress analysis) by means of an initial 200-N load for 5,000 cycles and subsequent increase of 50 N (step-size) at each 10,000 cycles, until failure occurred. The load at failure and number of cycles until failure were recorded; survival probabilities and specimen displacement were calculated for each step. The failure pattern was evaluated, and the Weibull modulus was obtained for each condition. Fatigue of both types of crowns was not influenced by the abutment material (LD-PEEK = LD-YZ; TZ-PEEK = TZ-YZ). In the PEEK abutment, the values obtained in the LD and TZ crowns showed no statistical difference; however, in the YZ abutment, the TZ crown presented a load at failure value that was statistically higher than that for LD. Failure pattern analysis revealed a higher prevalence of crown fracture for LD groups, while screw/implant platform fractures were shown for TZ groups. YZ and PEEK hybrid abutments promoted similar fatigue levels regardless of the crown materials, TZ crowns promoted a higher fatigue level than LD ones when associated with YZ abutments, and LD crowns promoted a similar fatigue level to TZ ones when associated with PEEK custom abutments. Higher prevalence of crown fractures was shown for LD and screw/implant platform fractures for TZ groups.

Is Clinical Target Volume Necessary? A Failure Pattern Analysis in Patients with Locally Advanced Non-Small Cell Lung Cancer Treated with Concurrent Chemoradiotherapy Using Intensity-Modulated Radiotherapy Technique

Background Our previous dosimetric study showed that for locally advanced non-small cell lung cancer (LA-NSCLC), radiotherapy with intensity-modulated radiotherapy (IMRT) technique could deliver sufficient dose coverage to subclinical regions and reduce the dose to normal tissues with the omission of clinical target volume (CTV). To further clinically validate this strategy, we conducted the current study to analyze the failure pattern for patients with LA-NSCLC treated with concurrent chemotherapy and CTV-omitted IMRT. We also investigated the effects of target volumes on lymphopenia during radiotherapy to further test the potential benefits of CTV omission in anti-tumor immunotherapy. Methods A total of 63 patients with LA-NSCLC treated with CTV-omitted IMRT with concurrent chemotherapy were enrolled in this study. Their planning target volume (PTV) (also PTV-g) was expanded directly from gross tumor volume (GTV). A virtual CTV was expanded from GTV, and the PTV generated from virtual CTV was named planning target volume with CTV expansion (PTV-c). Treatment failures were divided into local, regional, and distant failures, and local-regional recurrences were classified into inside PTV-g (IN-PTV-g), between PTV-g and PTV-c (PTV-g-c), and outside PTV-c (OUT-PTV-c). The relationship between lymphopenia during radiotherapy and the target volumes was also evaluated using Spearman's correlation analysis. Results Among the 60 patients with detailed follow-up data for recurrences, 46 (76.7%) experienced recurrences, with 18 (30.0%) being local recurrence, 5 (8.4%) being regional failure, and 33 (55.0%) being distant failure. For the 21 patients with local-regional recurrences, 16, 6, and 1 were IN-PTV-g, OUT-PTV-c, and PTV-g-c recurrences, respectively. Lymphopenia during radiotherapy was associated with both GTV and PTV, with larger volumes linked to severe lymphopenia. Conclusions CTV omission is feasible for LA-NSCLC treated with concurrent chemoradiotherapy and does not compromise failure inside the subclinical region. The radiation volumes were associated with lymphopenia during radiotherapy, with larger volumes related to severe lymphopenia. This finding supports the further exploration of CTV omission for immunotherapy.

A Comparative Analysis of Failure Patterns for Different Pathological Types of Primary Sinonasal Malignancies

A Comparative Analysis of Failure Patterns for Different Pathological Types of Primary Sinonasal Malignancies

Is clinical target volume necessary?-a failure pattern analysis in patients with locally advanced non-small cell lung cancer treated with concurrent chemoradiotherapy using intensity-modulated radiotherapy technique.

BackgroundOur previous dosimetric study showed that for locally advanced non-small cell lung cancer (LA-NSCLC), radiotherapy with intensity-modulated radiotherapy (IMRT) technique could deliver sufficient dose coverage to subclinical regions and reduce the dose to normal tissues with the omission of clinical target volume (CTV). To further clinically validate this strategy, we conducted the current study to analyze the failure pattern for patients with LA-NSCLC treated with concurrent chemotherapy and CTV-omitted IMRT. We also investigated the effects of target volumes on lymphopenia during radiotherapy to further test the potential benefits of CTV omission in anti-tumor immunotherapy.MethodsA total of 63 patients with LA-NSCLC treated with CTV-omitted IMRT with concurrent chemotherapy were enrolled in this study. Their planning target volume (PTV) (also PTV-g) was expanded directly from gross tumor volume (GTV). A virtual CTV was expanded from GTV, and the PTV generated from virtual CTV was named planning target volume with CTV expansion (PTV-c). Treatment failures were divided into local, regional, and distant failures, and local–regional recurrences were classified into inside PTV-g (IN-PTV-g), between PTV-g and PTV-c (PTV-g-c), and outside PTV-c (OUT-PTV-c). The relationship between lymphopenia during radiotherapy and the target volumes was also evaluated using Spearman’s correlation analysis.ResultsAmong the 60 patients with detailed follow-up data for recurrences, 46 (76.7%) experienced recurrences, with 18 (30.0%) being local recurrence, 5 (8.4%) being regional failure, and 33 (55.0%) being distant failure. For the 21 patients with local–regional recurrences, 16, 6, and 1 were IN-PTV-g, OUT-PTV-c, and PTV-g-c recurrences, respectively. Lymphopenia during radiotherapy was associated with both GTV and PTV, with larger volumes linked to severe lymphopenia.ConclusionsCTV omission is feasible for LA-NSCLC treated with concurrent chemoradiotherapy and does not compromise failure inside the subclinical region. The radiation volumes were associated with lymphopenia during radiotherapy, with larger volumes related to severe lymphopenia. This finding supports the further exploration of CTV omission for immunotherapy.

Is it necessary to pre-treat Dentine before GIC Restorations? Evidence from an in Vitro Study.

The aim of this study was to assess the influence of different pre-treatment approaches on glass ionomer cement (GIC) bond strength (BS) to dentine. Sixty bovine incisors were allocated into six groups according to substrate - sound or caries-affected dentine; and substrate pre-treatment approach - no conditioning (control), polyacrylic acid for 10 s and phosphoric acid for 7 s. Teeth in the caries-affected dentine group were previously submitted to cariogenic pH-cycling challenge. After dentine pre-treatment, according to experimental groups, polyethylene tubes were placed on flat dentine surfaces and filled with GIC. Teeth were stored in distilled water for 24 h at 37 °C and then submitted to microshear test (0.5 mm/min). Failure pattern analysis was performed under stereomicroscope (400x). Data were analysed using two-way ANOVA and Tukey's test (α=5%). Statistically significant differences were found for the pre-treatment approach, regardless of substrate (p<0.001). The polyacrylic acid group and control group had similar BS values, and were both better than the phosphoric acid group. In general, GIC had better bonding performance in sound dentine than in caries-affected dentine. In conclusion, dentine pre-treatment with polyacrylic acid did not improve the performance of GIC restoration on clinically relevant substrates.

Discrete and Continuous Approaches for the Failure Analysis of Masonry Structures Subjected to Settlements

Numerical modelling of masonry structures is nowadays still an active research field, given a number of open issues related to preservation and restoration of historical constructions and the availability of computational tools that have become more and more refined. This work focuses on the analysis of settlement-induced failure patterns characterizing the in plane response of two-dimensional dry-joints masonry panels, which differ in terms of texture, geometry and settlement configuration. Brick-block masonry, interpreted as a jointed assembly of prismatic particles in dry contact, can be modelled as a discrete system of rigid blocks interacting through contact surfaces with no tensile strength and finite friction, modelled as zero thickness elasto-plastic Mohr-Coulomb interfaces. Different approaches and numerical models are adopted herein: Limit Analysis (LA), a discrete model DEM and a continuous Finite Element Model (FEM). Limit Analysis is able to provide fast and reliable results in terms of collapse multiplier and relative kinematics. In this work, a standard LA procedure is coded through Linearised Mathematical Programming to take into account sliding mechanisms through dilatant joints. Discrete models are particularly suitable to study historical masonry materials, where rigid bodies interacts between contact and friction. Here, a combined Finite/Discrete Element approach (FEM/DEM) is adopted. Finally, analyses are conducted through the Finite Element approach, resorting to a continuum anisotropic elastic-perfectly plastic constitutive model. Some selected case-studies have been investigated adopting the above mentioned models and numerical results have been interpreted to highlight the capability of the approaches to predict failure patterns for various geometrical features of the structure and settlement configurations.

Pattern of disease progression following stereotactic radiosurgery in malignant glioma patients

IntroductionThe clinical benefit of stereotactic radiosurgery (SRS) in the treatment of malignant glioma remains controversial. We analyzed failure patterns of malignant gliomas following SRS to identify the clinical implications of SRS against these malignancies. Materials and methodsWe retrospectively reviewed 58 consecutive patients who received SRS with a gamma knife for their malignant glioma from January 2013 to December 2018. A total of 51 patients were available for analysis of failure patterns. Failure patterns were defined by the recurrent tumors’ spatial relation to SRS target as follows: in-field local recurrence, remote recurrence, and leptomeningeal seeding. If patients demonstrated several types of failure patterns simultaneously, we categorized them as a combined failure pattern. ResultsIn-field local recurrence was found in 47.1% of patients. Other types of failure patterns were as follows: remote recurrence (19.6%), leptomeningeal seeding (13.7%), and combined failure pattern (19.6%). The majority of patients (52.9%) experienced disease progression beyond the radiation field of SRS, which implies limited efficacy of local therapy against these invasive tumors. The prognosis of patients differed according to failure pattern and patients with local recurrence had better survival outcomes compared to other types of disease progression (p-value = 0.0015, log-rank test). ConclusionsThis study illustrated that SRS could not improve survival of malignant gliomas significantly even when it had some effect within radiation field. Our findings support utilizing a multidisciplinary treatment strategy to improve the prognosis of malignant gliomas and suggest that SRS is one element of that treatment strategy.

Analysis of the Damage Characteristics and Energy Dissipation of Rocks with a Vertical Hole under Cyclic Impact Loads

This study systematically investigates the failure patterns, energy dissipation, and fracture behavior of rock specimens containing a vertical hole under impact loads. First, an improved damage calculation equation suitable for the analysis of rock specimens with a vertical hole is obtained based on the one‐dimensional stress wave theory and the interface continuity condition. After that, the Hopkinson pressure bar (SHPB) device was used to conduct cyclic impact tests with different impact pressures and impact modes (impact pressures with equal amplitude and unequal amplitude). The experimental results suggest that, under the equal‐amplitude high pressure and unequal‐amplitude pressure, the degree of damage of the rock significantly increased, the bearing capacity greatly reduced, and the rock gradually transitions from having good ductility to experiencing brittle failure. The cumulative specific energy absorption value gradually increases with the increase in the cyclic impact. Compared to that of the equal impact condition, the degree of damage to the rock is more severe for the case of equal‐amplitude high pressure and unequal impact, and the failure mode undergoes a transformation from transverse tensile failure to transverse tensile failure‐axial splitting failure combination and axial splitting failure. Through the analysis of rock energy changes and rock failure patterns during cyclic impact, it will be helpful to predict and control the fracture caused by local stress concentration during excavation, thus can reduce the cost of support and reinforcement in excavation and improve the stability of surrounding rocks.

Comparison of fracture strength after thermo-mechanical aging between provisional crowns made with CAD/CAM and conventional method.

PURPOSEThe objectives of this study were to evaluate the fracture strength and fracture patterns of provisional crowns fabricated from different materials and techniques after receiving stress from a simulated oral condition.MATERIALS AND METHODSA monomethacrylate-based resin (Unifast Trad) and a bis-acryl-based (Protemp 4) resin were used to fabricate provisional crowns using conventional direct technique. A milled monomethacrylate resin (Brylic Solid) and a 3D-printed bis-acrylate resin (Freeprint Temp) were chosen to fabricate provisional crowns using the CAD/CAM process. All cemented provisional crowns (n=10/group) were subjected to thermal cycling (5,000 cycles at 5°–55℃) and cyclic occlusal load (100 N at 4 Hz for 100,000 cycles). Maximum force at fracture was tested using a universal testing machine.RESULTSMaximum force at fracture (mean ± SD, N) of each group was 657.87 ± 82.84 for Unifast Trad, 1125.94 ± 168.07 for Protemp4, 953.60 ± 58.88 for Brylic Solid, and 1004.19 ± 122.18 for Freeprint Temp. One-way ANOVA with Tamhane post hoc test showed that the fracture strength of Unifast Trad was statistically significantly lower than others (P<.01). No statistically significant difference was noted among other groups. For failure pattern analysis, Unifast Trad and Brylic Solid showed less damage than Protemp 4 and Freeprint Temp groups.CONCLUSIONProvisional crowns fabricated using the CAD/CAM process and the conventionally fabricated bis-acryl resins exhibited significant higher fracture strength compared to conventionally fabricated monomethacrylate resins after the aging regimen. Therefore, CAD/CAM milling and 3D printing of provisional restorations may be good alternatives for long term provisionalization.

Retrofit Existing Frame Structures to Increase Their Economy and Sustainability in High Seismic Hazard Regions

The study proposes a retrofitting method with an optimum design of viscous dampers in order to improve the structural resistant capacity to earthquakes. The retrofitting method firstly uses a 2D frame model and places the viscous dampers in the structure to satisfy the performance requirements under code-specific design earthquake intensities and then performs an optimum design to increase the structural collapse-resistant capacity. The failure pattern analysis and fragility analysis show that the optimum design leads to better performance than the original frame structure. For regular structures, it is demonstrated that the optimum pattern of viscous damper placement obtained from a 2D frame model can be directly used in the retrofitting of the 3D frame model. The economic loss and repair time analyses are conducted for the retrofitted frame structure under different earthquake intensities, including the frequent earthquake, the occasional earthquake, and the rare earthquake. Although the proposed method is based on time-history analyses, it seems that the computational cost is acceptable because the 2D frame model is adopted to determine the optimum pattern of viscous damper placement; meanwhile, the owner can clearly know the economic benefits of the retrofitting under different earthquake intensities. The retrofitting also causes the frame to have reduced environmental problems (such as carbon emission) compared to the original frame in the repair process after a rare earthquake happens.

Effect of carbodiimide and chlorhexidine on the bond strength longevity of resin cement to root dentine after radiation therapy.

To evaluate the effect of carbodiimide (EDC) and chlorhexidine (CHX) on the bond strength (BS) of resin cement to root dentine of teeth submitted to radiotherapy. One hundred and twenty extracted maxillary canines were selected and assigned to 2 groups (n=60): nonirradiated and irradiated (30 cycles of 2Gy, total 60Gy). Roots lengths were standardized, and canals were prepared and filled. Post spaces were then prepared, and the samples were redistributed according to dentine treatment (n=20): saline solution (SF); CHX 2%; or EDC 0.5M. After drying the post space, fibreglass posts were cemented. Cross-sectioned slices were obtained, and in half of the specimens of each subgroup (n=10), the analysis was performed immediately; the others (n=10) were stored for 10months before analyses. The most cervical slice of each third was subjected to a push-out test and failure pattern analysis (n=10), and the most apical slice submitted to the analysis of the adhesive interface by SEM (n=5). The bond strength data were submitted to anova and Tukey tests, the adhesive interface adaptation was submitted to Kruskal-Wallis and Dunn's tests, and the Chi-square test was used to evaluate the type of failure. The irradiated specimens had significantly lower bond strength (13.8±4.3) than the nonirradiated (18.1±3.1; P<0.001). For the irradiated teeth, the bond strengths were significantly lower in the SF and CHX groups (P<0.001). Also, the bond strengths reduced significantly after 10months in the SF and CHX groups (P<0.001). Cohesive failures occurred in dentine for irradiated specimens. Poorer interface adaptation, dentine fractures and microfractures were observed in irradiated specimens, and better adaptation was observed for specimens after EDC treatment. Radiotherapy was associated with lower bond strength and worse interface adaptation. Dentine treatment with EDC contributed to adhesive interface longevity during the cementation of glass fibre posts in nonirradiated and irradiated teeth.

Ballistic performance of bioinspired nacre-like aluminium composite plates

Inspired by the hierarchical structure of nacre, an aluminium alloy (AA) 7075-T651 based composite plate is developed for ballistic applications. The proposed nacre-like composite plates are made of 5, 7 or 9 layers consisting of many ~1 mm thick AA7075-T651 tablets bonded together with toughened epoxy adhesive. Experimental ballistic tests on these composite plates, using a hemispherical nosed steel projectile at impact velocities in the range of 340–450 m/s, were performed. Both the 5-layer and 7-layer plates exhibited a better ballistic performance than their bulk counterparts based on the observation that the measured residual velocity of the projectile through the composite plate was lower than that through the corresponding bulk plate with similar areal density. However, the performance improvement is reduced as the composite plate thickness increases (from 5 to 9 layers) due to the increased likelihood of ductile failure occurring prior to perforation in the thicker bulk plates. The failure pattern analysis of the impacted specimens confirmed that the impact performance enhancement of the nacre-like composite plates can be attributed to the hierarchical structure facilitating both localized energy absorption (by tablet deformation and interlocking) and more globalized energy absorption (by inter-layer delamination and friction).

The Unique Spatial-Temporal Treatment Failure Patterns of Adjuvant Gefitinib Therapy: A Post Hoc Analysis of the ADJUVANT Trial (CTONG 1104)

IntroductionAdjuvant gefitinib therapy prolonged disease-free survival in patients with resected early-stage EGFR-mutation positive NSCLC in the ADJUVANT study (CTONG 1104). However, treatment failure patterns after gefitinib therapy are less well characterized. MethodsOverall, 222 stage N1–N2, EGFR-mutant NSCLC patients received gefitinib or vinorelbine plus cisplatin (VP) treatment. Tumor recurrences or metastases occurring during follow-up were defined as treatment failure; sites and data of first treatment failure were recorded. A post hoc analysis of treatment failure patterns which was estimated by Kaplan-Meier and hazard rate curves in modified intention-to-treat patients was conducted. ResultsThere were 114 recurrences and 10 deaths before recurrence across 124 progression events. Spatial distribution analysis showed that the first metastasis site was most frequently the central nervous system in the gefitinib group (29 of 106 [27.4%]), extracranial metastases were most frequent in the VP group (32 of 87 [36.8%]). Temporal distribution analysis showed lower tumor recurrence with gefitinib than with VP 0 to 21 months post-surgery. However, recurrence with gefitinib showed a constant rate of increase 12 months post-surgery. The first peak of extracranial metastasis appeared during 9 to 15 months with VP and 24 to 30 months with gefitinib. The highest peak for central nervous system metastases post-surgery occurred after 12 to 18 months with VP and 24 to 36 months with gefitinib. ConclusionsAdjuvant gefitinib showed advantages over VP chemotherapy in treatment failure patterns especially in extracranial metastasis. Adjuvant tyrosine kinas inhibitors may be considered as a treatment option in resected stage N1–N2 EGFR-mutant NSCLC but longer duration should be explored.

Mechanical anisotropy of jointed rock mass under uniaxial compression and tensile loading

Anisotropic in a rock mass are the properties which have directional mechanical behaviours. These anisotropic characteristics are originated from foliation of minerals in metamorphic rock, stratification in sedimentary rocks and discontinuities in the rock mass. The strength and deformability of rock mass are influenced by the orientation and distribution of fractured networks and the failure mode is varies significantly with the variation of fracture orientation. Therefore, the mechanical behaviour of rock mass becomes one of the most crucial topics in rock engineering fields. In this paper, stratified and jointed limestone samples from two different quarries of Ipoh areas (LafargeHolcim and Hume Cement) were studied to determine the mechanical strength and failure patterns under uniaxial compression and tensile loading. The results showed that the failure pattern and maximum strength of was correlated with relative layer orientations. It was observed that the higher the inclination angle the lower the failure strength. The maximum tensile strength also observed at 0° with 16.77 MPa and the lowest occurred at 75° which are 5.68 MPa. The highest compression loaded at 0° which to break at 104.81 MPa and the lowest occurred at 75° which are 40.38 MPa. It is suggested that the failure pattern analysis should be considered in mechanical study of jointed rock mass.

Local recurrence patterns after postoperative stereotactic radiation surgery to resected brain metastases: A quantitative analysis to guide target delineation

PurposeIn the treatment of resected metastatic brain disease, a recent phase 3 trial by the North Central Cancer Treatment Group (N107C/CEC.3) surprisingly found that the local control rate for whole-brain radiation therapy was better than that of stereotactic radiation surgery (SRS). To optimize target delineation, we performed a quantitative analysis of local failure patterns after postoperative SRS. Methods and materialsPatients with brain metastases who were treated with surgery and SRS to the cavity were evaluated. Local failure was defined by pathologic confirmation or magnetic resonance imaging evidence of progression leading to further overlapping radiation therapy. T1 postgadolinium magnetic resonance imaging scans that were taken preoperatively and at recurrence were co-registered to the simulation computed tomography. Three volumes were compared: (1) Preoperative tumors, (2) resection cavities that were originally contoured as clinical target volumes for SRS, and (3) recurrent tumors. Overlap volume histograms quantified the proximity of the three volumes to the meninges. ResultsIn the cohort of 173 patients, 18 patients experienced local failure in 19 resection cavities. The original SRS target volume overlapped with a median of 69.6% of the recurrent tumor. When the entire preoperative tumor was included, the overlap with the recurrent tumor increased to a median of 76.8%. Recurrent tumors were closer to the meninges than corresponding preoperative tumors (P = .03) but a median 8.2 mm expansion of the target volume from the meninges was needed to increase overlap with the recurrent tumor to 90%. Increases in overlap with the recurrent tumor were achieved most efficiently by uniformly expanding the contoured cavity and a median 2.8 mm expansion covered 90% of the recurrent tumor. ConclusionsOur quantitative analysis of recurrence patterns suggests that a larger 3 mm uniform expansion of the SRS target volume substantially increases coverage of the volume that is later occupied by the recurrent tumor and may provide improved local control. The extent of the preoperative tumor in the target volume or expanding the target volume from the meninges provides little benefit.

Multi-institutional competing risks analysis of distant brain failure and salvage patterns after upfront radiosurgery without whole brain radiotherapy for brain metastasis

In this study, we use a competing risks analysis to assess factors predictive of early-salvage whole brain radiotherapy (WBRT) and early death after upfront stereotactic radiosurgery (SRS) alone for brain metastases in an attempt to identify populations that benefit less from upfront SRS. Patients from eight academic centers were treated with SRS for brain metastasis. Competing risks analysis was carried out for distant brain failure (DBF) versus death prior to DBF as well as for salvage SRS versus salvage WBRT versus death prior to salvage. Linear regression was used to determine predictors of the number of brain metastases at initial DBF (nDBF). A total of 2657 patients were treated with upfront SRS alone. Multivariate analysis (MVA) identified an increased hazard of DBF associated with increasing number of brain metastases (P < 0.001), lowest SRS dose received (P < 0.001), and melanoma histology (P < 0.001), while there was a decreased hazard of DBF associated with increasing age (P < 0.001), KPS < 70 (P < 0.001), and progressive systemic disease (P = 0.004). MVA for first salvage SRS versus WBRT versus death prior to salvage revealed an increased hazard of first salvage WBRT seen with increasing number of brain metastases (P < 0.001) and a decreased hazard with widespread systemic disease (P = 0.002) and increasing age (P < 0.001). Variables associated with nDBF included age (P = 0.02), systemic disease status (P = 0.03), melanoma histology (P = 0.05), and initial number of brain metastases (P < 0.001). Patients with a higher initial number of brain metastases were more likely to experience DBF, have a higher nDBF, and receive early-salvage WBRT, while patients who were older, had lower KPS, or had more systemic disease were more likely to experience death prior to DBF or salvage WBRT.

Prognostic Significance of Serum CEA for Non-small Cell Lung Cancer Patients Receiving Stereotactic Body Radiotherapy.

To examine the prognostic significance of serum carcinoembryonic antigen (CEA) for stage I non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT). In total, 129 stage I NSCLC patients were analyzed and divided into two groups: CEA-High (CEA>5 ng/ml) and CEA-Low (CEA≤5 ng/ml). Median follow-up time was 38 months. Overall survival was not significantly different between CEA-High (n=47) and CEA-Low (n=82) patients (57% vs. 63% at 3 years; p=0.39), although progression-free survival (PFS) was significantly worse in CEA-High patients (31% vs. 51% at 3 years; p=0.01). Larger tumor size and high CEA level were independent prognostic factors for worse PFS. Failure pattern analysis showed that regional node or distant recurrence was more common in CEA-High patients (47%) than in CEA-Low patients (29%). Patients with CEA-High stage I NSCLC have a higher risk of regional or systemic relapse and should be followed-up carefully.