13 research outputs found

    Addition of MRI for CT-based pancreatic tumor delineation:a feasibility study

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    To assess the effect of additional magnetic resonance imaging (MRI) alongside the planning computed tomography (CT) scan on target volume delineation in pancreatic cancer patients. Eight observers (radiation oncologists) from six institutions delineated the gross tumor volume (GTV) on 3DCT, and internal GTV (iGTV) on 4DCT of four pancreatic cancer patients, while MRI was available in a second window (CT + MRI). Variations in volume, generalized conformity index (CIgen), and overall observer variation, expressed as standard deviation (SD) of the distances between delineated surfaces, were analyzed. CIgen is a measure of overlap of the delineated iGTVs (1 = full overlap, 0 = no overlap). Results were compared with those from an earlier study that assessed the interobserver variation by the same observers on the same patients on CT without MRI (CT-only). The maximum ratios between delineated volumes within a patient were 6.1 and 22.4 for the GTV (3DCT) and iGTV (4DCT), respectively. The average (root-mean-square) overall observer variations were SD = 0.41 cm (GTV) and SD = 0.73 cm (iGTV). The mean CIgen was 0.36 for GTV and 0.37 for iGTV. When compared to the iGTV delineated on CT-only, the mean volumes of the iGTV on CT + MRI were significantly smaller (32%, Wilcoxon signed-rank, p  < .0005). The median volumes of the iGTV on CT + MRI were included for 97% and 92% in the median volumes of the iGTV on CT. Furthermore, CT + MRI showed smaller overall observer variations (root-mean-square SD = 0.59 cm) in six out of eight delineated structures compared to CT-only (root-mean-square SD = 0.72 cm). However, large local observer variations remained close to biliary stents and pathological lymph nodes, indicating issues with instructions and instruction compliance. The availability of MRI images during target delineation of pancreatic cancer on 3DCT and 4DCT resulted in smaller target volumes and reduced the interobserver variation in six out of eight delineated structure

    Preoperative Chemoradiotherapy Versus Immediate Surgery for Resectable and Borderline Resectable Pancreatic Cancer:Results of the Dutch Randomized Phase III PREOPANC Trial

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    PURPOSE Preoperative chemoradiotherapy may improve the radical resection rate for resectable or borderline resectable pancreatic cancer, but the overall benefit is unproven.PATIENTS AND METHODS In this randomized phase III trial in 16 centers, patients with resectable or borderline resectable pancreatic cancer were randomly assigned to receive preoperative chemoradiotherapy, which consisted of 3 courses of gemcitabine, the second combined with 15 x 2.4 Gy radiotherapy, followed by surgery and 4 courses of adjuvant gemcitabine or to immediate surgery and 6 courses of adjuvant gemcitabine. The primary end point was overall survival by intention to treat.RESULTS Between April 2013 and July 2017, 246 eligible patients were randomly assigned; 119 were assigned to preoperative chemoradiotherapy and 127 to immediate surgery. Median overall survival by intention to treat was 16.0 months with preoperative chemoradiotherapy and 14.3 months with immediate surgery (hazard ratio, 0.78; 95% CI, 0.58 to 1.05; P = .096). The resection rate was 61% and 72% (P = .058). The R0 resection rate was 71% (51 of 72) in patients who received preoperative chemoradiotherapy and 40% (37 of 92) in patients assigned to immediate surgery (P &lt;.001). Preoperative chemoradiotherapy was associated with significantly better disease-free survival and locoregional failure-free interval as well as with significantly lower rates of pathologic lymph nodes, perineural invasion, and venous invasion. Survival analysis of patients who underwent tumor resection and started adjuvant chemotherapy showed improved survival with preoperative chemoradiotherapy (35.2 v 19.8 months; P = .029). The proportion of patients who suffered serious adverse events was 52% versus 41% (P = .096).CONCLUSION Preoperative chemoradiotherapy for resectable or borderline resectable pancreatic cancer did not show a significant overall survival benefit. Although the outcomes of the secondary end points and predefined subgroup analyses suggest an advantage of the neoadjuvant approach, additional evidence is required.</p

    Neoadjuvant Chemoradiotherapy Versus Upfront Surgery for Resectable and Borderline Resectable Pancreatic Cancer:Long-Term Results of the Dutch Randomized PREOPANC Trial

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    PURPOSE: The benefit of neoadjuvant chemoradiotherapy in resectable and borderline resectable pancreatic cancer remains controversial. Initial results of the PREOPANC trial failed to demonstrate a statistically significant overall survival (OS) benefit. The long-term results are reported. METHODS: In this multicenter, phase III trial, patients with resectable and borderline resectable pancreatic cancer were randomly assigned (1:1) to neoadjuvant chemoradiotherapy or upfront surgery in 16 Dutch centers. Neoadjuvant chemoradiotherapy consisted of three cycles of gemcitabine combined with 36 Gy radiotherapy in 15 fractions during the second cycle. After restaging, patients underwent surgery followed by four cycles of adjuvant gemcitabine. Patients in the upfront surgery group underwent surgery followed by six cycles of adjuvant gemcitabine. The primary outcome was OS by intention-to-treat. No safety data were collected beyond the initial report of the trial. RESULTS: Between April 24, 2013, and July 25, 2017, 246 eligible patients were randomly assigned to neoadjuvant chemoradiotherapy (n = 119) and upfront surgery (n = 127). At a median follow-up of 59 months, the OS was better in the neoadjuvant chemoradiotherapy group than in the upfront surgery group (hazard ratio, 0.73; 95% CI, 0.56 to 0.96; P = .025). Although the difference in median survival was only 1.4 months (15.7 months v 14.3 months), the 5-year OS rate was 20.5% (95% CI, 14.2 to 29.8) with neoadjuvant chemoradiotherapy and 6.5% (95% CI, 3.1 to 13.7) with upfront surgery. The effect of neoadjuvant chemoradiotherapy was consistent across the prespecified subgroups, including resectable and borderline resectable pancreatic cancer. CONCLUSION: Neoadjuvant gemcitabine-based chemoradiotherapy followed by surgery and adjuvant gemcitabine improves OS compared with upfront surgery and adjuvant gemcitabine in resectable and borderline resectable pancreatic cancer

    Survival after Definitive (Chemo)Radiotherapy in Esophageal Cancer Patients:A Population-Based Study in the North-East Netherlands

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    <p>Definitive (chemo)radiotherapy is employed in esophageal cancer patients as an alternative for patients considered medically unfit for surgery or having unresectable tumors. We evaluated a population-based cohort to improve the selection for intensified nonsurgical strategies and to identify prognostic factors.</p><p>Patients who had squamous cell carcinoma (SCC) or adenocarcinoma (AC) were treated in four referral centers in the north-east Netherlands with definitive chemoradiotherapy (dCRT) or radiotherapy (dRT) between 1996 and 2008.</p><p>Of the 287 included patients, 110 were treated with dCRT and 177 with dRT. Median overall survival (OS) was 11 months (95 % confidence interval: 10-12 months), with OS of 22 and 8 % and disease-free survival (DFS) of 16 and 5 % at 2 and 5 years, respectively. DFS at 2 and 5 years was 24 and 9 % for SCC versus 10 and 2 % for AC patients (P = 0.006). OS after 2 and 5 years was 29 and 14 % for SCC patients versus 17 and 3 % for AC patients (P = 0.044). On multivariate Cox regression, SCC was an independent prognostic factor for DFS [P = 0.020, hazard ratio (HR) = 0.71] and OS (P = 0.047, HR = 0.76). On matched cohort analysis, DFS was higher in the dCRT group compared with dRT patients (P = 0.016). The locoregional failure rate was lower in the dCRT group and in SCC patients (P = 0.001 and 0.046).</p><p>Long-term results and the local control rate in SCC patients were better after definitive (chemo)radiotherapy compared with in AC patients. SCC was an independent prognostic factor for survival. Definitive chemoradiotherapy leads to improved local control rate and DFS.</p>

    Computational methods of linear algebra

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    Applications of Asteroseismology

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    Mode Identification

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    Introducing Asteroseismology

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    Frequency Analysis

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