Computational Study of Hemodynamic Changes Induced by Overlapping and Compacting of Stents and Flow Diverter in Cerebral Aneurysms

Purpose: The flow diversion effect of an intracranial stent is closely related to its metal coverage rate (MCR). In this study, the flow diversion effects of Enterprise and low-profile visualized intraluminal support (LVIS) stents are compared with those of a Pipeline flow diverter, focusing on the MCR change. Moreover, the changes in the flow diversion effect caused by the additional manipulations of overlapping and compaction are verified using computational fluid dynamics (CFD) analysis. Methods: CFD analysis was performed using virtually generated stents mounted in an idealized aneurysm model. First, the flow diversion effects of single Enterprise, LVIS, and Pipeline devices were analyzed. The Enterprise and LVIS were sequentially overlapped and compared with a Pipeline, to evaluate the effect of stent overlapping. The effect of compacting a stent was evaluated by comparing the flow diversion effects of a single and two compacted LVIS with those of two overlapped, uncompacted LVIS and uncompacted and compacted Pipeline. Quantitative analysis was performed to evaluate the hemodynamic parameters of energy loss, average velocity, and inflow rate. Results: Statistically significant correlations were observed between the reduction rates of the hemodynamic parameters and MCR. The single LVIS without compaction induced a reduction in all the hemodynamic parameters comparable to those of the three overlapped Enterprise. Moreover, the two overlapped, uncompacted LVIS showed a flow diversion effect as large as that induced by the single uncompacted Pipeline. Compacted stents induced a better flow diversion effect than uncompacted stents. The single compacted LVIS induced a flow diversion effect similar to that induced by the two uncompacted LVIS or single uncompacted Pipeline. Conclusions: The MCR of a stent correlates with its flow diversion effect. Overlapping and compaction can increase the MCR of an intracranial stent and achieve a flow diversion effect as large as that observed with a flow diverter.ope

The quantitative comparison between high wall shear stress and high strain in the formation of paraclinoid 무뎌교는

In the hemodynamic study, computational fluid dynamics (CFD) analysis has shown that high wall shear stress (WSS) is an important parameter in cerebral aneurysm formation. However, CFD analysis is not more realistic than fluid-structure interaction (FSI) analysis given its lack of considering the involvement of vascular structures. To investigate the relationship between the hemodynamic parameters and the aneurysm formation, the locations of high WSS and high strain were extracted from the CFD and FSI analyses, respectively. Then the distances between the aneurysm formation site and the locations of high WSS or high strain were calculated. A total of 37 intracranial paraclinoid aneurysms were enrolled for quantitative comparison. Additionally, the dura mater was modeled to facilitate realistic results in FSI analysis. The average distance from the location of the aneurysm formation site to the high strain (1.74 mm [Formula: see text] 1.04 mm) was smaller than the average distance to the high WSS (3.33 mm [Formula: see text] 1.18 mm). The presence of dura mater also influenced the findings in the aneurysm formation site. High strain extracted by FSI analysis is an important hemodynamic factor related to the formation of cerebral aneurysms. Strain parameter could help to predict the formation of aneurysms and elucidate the appropriate treatment.ope

Internal mammary node irradiation in node-positive breast cancer treated with mastectomy and taxane-based chemotherapy

Background: It is important to continually reevaluate the risk/benefit calculus of internal mammary node irradiation (IMNI) in the era of modern systemic therapy. We aimed to investigate the effect of IMNI on survival in node-positive breast cancer treated with mastectomy and anthracycline plus taxane-based chemotherapy. Methods: We analyzed 348 patients who underwent mastectomy and anthracycline plus taxane-based chemotherapy for node-positive breast cancer between January 2006 and December 2011. All patients received postoperative radiation therapy (RT) with IMNI (n = 105, 30.2%) or without IMNI (n = 243, 69.8%). The benefit of IMNI for disease-free survival (DFS) and overall survival (OS) was evaluated using multivariate analysis and inverse probability of treatment weighting (IPTW) to adjust for unbalanced covariates between the groups. Results: After a median follow-up of 95 months, the 10-year locoregional recurrence-free survival rate, DFS, and OS in all patients were 94.8%, 77.4%, and 86.2%, respectively. The IPTW-adjusted hazard ratio (HR) for the association of IMNI (vs. no IMNI) with DFS and OS was 0.208 (95% confidence intervals (CI) 0.045-0.966) and 0.460 (95% CI, 0.220-0.962), respectively. In multivariate analysis, IMNI was a favorable factor for DFS (HR, 0.458; P = 0.021) and OS (HR 0.233, P = 0.018). Conclusions: IMNI was associated with improved DFS and OS in node-positive patients treated with mastectomy, post-mastectomy RT, and taxane-based chemotherapy, although the rate of locoregional recurrence was low.ope

Journey to hypofractionation in radiotherapy for breast cancer: critical reviews for recent updates

Historical conventional fractionated radiation therapy (RT) for breast cancer consisted of 1.8-2.0 Gy per fraction with a total dose of 45-60 Gy over 5-7 weeks. Based on radiobiological characteristics, a low α/β is suspected of breast cancer resulting in sensitivity to higher dose per fraction (2.5-3.0 Gy). Over the past 10 years, multiple clinical trials support the application of shorter treatment regimen with hypofractionated RT (HypoRT). Recently, ultra-HypoRT with 5 fractions showed favorable outcomes. Although the safety and efficacy of HypoRT has been supported by high-quality randomized trials, there are still some worries and doubts around HypoRT from radiation oncologists. However, the radiation oncology community have now reached an important timepoint for adopting HypoRT during the COVID-19 pandemic. The aim of this review is to provide an overview of HypoRT in breast cancer based on prospective randomized trials and discuss the special consideration regarding HypoRT.ope

Current status of brachytherapy in Korea: a national survey of radiation oncologists.

OBJECTIVE: The aim of the present study was to acquire information on brachytherapy resources in Korea through a national survey of radiation oncologists. METHODS: Between October 2014 and January 2015, a questionnaire on the current status of brachytherapy was distributed to all 86 radiation oncology departments in Korea. The questionnaire was divided into sections querying general information on human resources, brachytherapy equipment, and suggestions for future directions of brachytherapy policy in Korea. RESULTS: The response rate of the survey was 88.3%. The average number of radiation oncologists per center was 2.3. At the time of survey, 28 centers (36.8%) provided brachytherapy to patients. Among the 28 brachytherapy centers, 15 (53.5%) were located in in the capital Seoul and its surrounding metropolitan areas. All brachytherapy centers had a high-dose rate system using (192)Ir (26 centers) or (60)Co (two centers). Among the 26 centers using (192)Ir sources, 11 treated fewer than 40 patients per year. In the two centers using (60)Co sources, the number of patients per year was 16 and 120, respectively. The most frequently cited difficulties in performing brachytherapy were cost related. A total of 21 centers had a plan to sustain the current brachytherapy system, and four centers noted plans to upgrade their brachytherapy system. Two centers stated that they were considering discontinuation of brachytherapy due to cost burdens of radioisotope source replacement. CONCLUSION: The present study illustrated the current status of brachytherapy in Korea. Financial difficulties were the major barriers to the practice of brachytherapy.ope

Postmastectomy Radiotherapy in Patients with pT1-2N1 Breast Cancer Treated with Taxane-Based Chemotherapy: A Retrospective Multicenter Analysis (KROG 1418)

Purpose: The purpose of this study was to evaluate the impact of postmastectomy radiotherapy (PMRT) on loco-regional recurrence-free survival (LRRFS), disease-free survival (DFS), and overall survival (OS) in pT1-2N1 patients treated with taxane-based chemotherapy. Materials and methods: We retrospectively reviewed the medical data of pathological N1 patients who were treated with modified radical mastectomy and adjuvant taxane-based chemotherapy in 12 hospitals between January 2006 and December 2010. Results: We identified 714 consecutive patients. The median follow-up duration was 69 months (range, 1 to 114 months) and the 5-year LRRFS, DFS, and OS rates were 97%, 94%, and 98%, respectively, in patients who received PMRT (PMRT [+]). The corresponding figures were 96%, 90%, and 96%, respectively, in patients who did not receive PMRT (PMRT [-]). PMRT had no significant impact on survival. Upon multivariable analysis, only the histological grade (HG) was statistically significant as a prognostic factor for LRRFS and DFS. In a subgroup analysis of HG 3 patients, PMRT (+) showed better DFS (p=0.081). Conclusion: PMRT had no significant impact on LRRFS, DFS, or OS in pT1-2N1 patients treated with taxane-based chemotherapy. PMRT showed a marginal benefit for DFS in HG 3 patients. Randomized studies are needed to confirm the benefit of PMRT in high risk patients, such as those with HG 3.ope

Comparison of Breast Conserving Surgery Followed by Radiation Therapy with Mastectomy Alone for Pathologic N1 Breast Cancer Patients in the Era of Anthracycline Plus Taxane-Based Chemotherapy: A Multicenter Retrospective Study (KROG 1418)

Purpose: We compared the oncologic outcomes of breast-conserving surgery plus radiation therapy (BCS+RT) and modified radical mastectomy (MRM) under anthracycline plus taxane-based (AT) regimens and investigated the role of adjuvant radiation therapy (RT) in patients with pathologic N1 (pN1) breast cancer treated by mastectomy. Materials and methods: We retrospectively reviewed the medical records of 2,011 patients with pN1 breast cancer who underwent BCS+RT or MRM alone at 12 institutions between January 2006 and December 2010. Two-to-one propensity score matching was performed for balances in variables between the groups. Results: The median follow-up duration for the total cohort was 69 months (range, 1 to 114 months). After propensity score matching, 1,074 patients (676 in the BCS+RT group and 398 in the MRM-alone group) were analyzed finally. The overall survival, disease-free survival, locoregional failure-free survival, and regional failure-free survival (RFFS) curves of the BCS+RT group vs. MRM-alone group were not significantly different. The subgroup analysis revealed that in the group with both lymphovascular invasion (LVI) and histologic grade (HG) III, the BCS+RT showed significantly superior RFFS (p=0.008). Lymphedema (p=0.007) and radiation pneumonitis (p=0.031) occurred more frequently in the BCS+RT group than in the MRM-alone group, significantly. Conclusion: There are no differences in oncologic outcomes between BCS+RT and MRM-alone groups under the AT chemotherapy regimens for pN1 breast cancer. However, BCS+RT group showed superior RFFS to MRM-alone group in the patients with LVI and HG III. Adjuvant RT might be considerable for pN1 breast cancer patients with LVI and HG III.ope

Prognostic factors of dose-response relationship for nodal control in metastatic lymph nodes of cervical cancer patients undergoing definitive radiotherapy with concurrent chemotherapy

Objective: Regional control is occasionally unsatisfactory in cervical cancer, with the optimal radiation dose for nodal metastases in definitive radiotherapy (RT) with concurrent chemotherapy (CRT) remaining controversial. We investigated dose-response relationship for nodal local control in cervical cancer. Methods: We identified 115 patients with 417 metastatic nodes who received definitive CRT for cervical cancer with nodal metastases. External beam radiation therapy and brachytherapy plans were summated to determine total dose received by each node. Prognostic factors of nodal control and dose-response relationship were investigated using Cox-regression and restricted cubic spline function. Results: The 2-year progression-free survival rate was 69.4%. Among 43 patients with failures, 17 patients (37.5%) had regional failure included in first failure sites of which all except one were in-field only regional failures. Total 30 nodes showed recurrence at initial metastatic site after treatment. Neutrophil-to-lymphocyte ratio (NLR) ≥3.1, total radiation dose (minimum dose received by 98% of the target volume in equivalent dose in 2 Gy per fractions), and initial nodal volume ≥5.29 mL were poor prognostic factors (all p<0.050) of nodal local control. Restricted cubic spline functions revealed strongest dose-response relationship in high NLR (NLR ≥3.1) and initial nodal volume ≥5.29 mL subgroup. Conclusion: Initial nodal volume, radiation dose, and NLR were significant factors of nodal local control in cervical cancer; a stronger dose-response relationship was seen in bulky nodes with high NLR. Clinicians may consider these factors when determining the RT dose and the need for boost to nodal metastases in cervical cancer.ope

Possible benefits from post-mastectomy radiotherapy in node-negative breast cancer patients: a multicenter analysis in Korea (KROG 14-22)

Purpose: This study was performed to identify a subset of patients who may benefit from post-mastectomy radiotherapy (PMRT) among node-negative breast cancer patients. Materials and methods: We retrospectively reviewed 1,828 patients with pT1-2N0 breast cancer, treated with mastectomy without PMRT from 2005 to 2010 at 10 institutions. Univariate and multivariate analyses for locoregional recurrence (LRR) and any first recurrence (AFR) were performed according to clinicopathologic factors and biologic subtypes. Results: During a median follow-up period of 5.9 years (range: 0.7-10.4 years), 98 patients developed AFR (39 isolated LRR, 13 LRR with synchronous distant metastasis, and 46 isolated distant metastasis), and 52 patients developed LRR. The 7-year LRR and AFR rates were 3.8% and 6.7%, respectively. Multivariate analysis revealed that age of ≤ 40 years (p<0.001) and T2 stage (p=0.013) were independent risk factors for LRR. The 7-year LRR rates were 2.5% with no risk factors, 4.5% with one risk factor, and 12.4% with two risk factors. Multivariate analysis for AFR revealed that age of ≤ 40 years (p<0.001), T2 stage (p<0.001), and triple-negative biological subtype (p=0.045) were independent risk factors for AFR. The 7-year AFR rates were 3.9% with no risk factors, 8.4% with one risk factor, and 15.7% with two to three risk factors. Conclusions: Mastectomy without PMRT is a sufficient local treatment for pT1-2N0M0 breast cancer. Nevertheless, PMRT might be considered for patients with two or three risk factors, among those of young age, with T2 tumors, and with the triple-negative biological subtype based on LRR and AFR.ope

Prediction of rupture risk in cerebral aneurysms by comparing clinical cases with fluid-structure interaction analyses

Cerebral aneurysms should be treated on the basis of accurate rupture risk prediction. Nowadays, the rupture risk in aneurysms has been estimated using hemodynamic parameters. In this paper, we suggest a new way to predict the rupture risks in cerebral aneurysms by using fluid-structure interaction (FSI) analysis for better decision-making regarding treatment. A patient-specific model was constructed using digital subtraction angiography of 51 cerebral aneurysms. For each model, a thin-walled area (TWA) was first predicted using computational fluid dynamics (CFD), and then the highest equivalent strain in the TWA was calculated with FSI by varying wall thicknesses and mechanical properties. A critical curve was made from 16 FSI results for each patient-specific model to estimate the rupture risk. On average, the equivalent strains of the ruptured aneurysms were higher than those of the unruptured aneurysms. Furthermore, the patterns of critical curves between unruptured and ruptured aneurysms were clearly distinguishable. From the rupture risk evaluation based on the cut-off value, 24 of the 27 unruptured aneurysms and 15 of the 24 ruptured aneurysms were matched with actual-clinical setting cases. The critical curve proposed in the present study could be an effective tool for the prediction of the rupture risk of aneurysm.ope