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OBJECTIVE: To describe the pooled learning curves of Ivor Lewis totally minimally invasive esophagectomy (TMIE) in hospitals stratified by predefined hospital- and surgeon-related factors.BACKGROUND: Ivor Lewis (TMIE is known to have a long learning curve which is associated with considerable learning associated morbidity. It is unknown whether hospital and surgeon characteristics are associated with more efficient learning.METHODS: A retrospective analysis of prospectively collected data of consecutive Ivor Lewis TMIE patients in 14 European hospitals was performed. Outcome parameters used as proxy for efficient learning were learning curve length, learning associated morbidity, and the plateau level regarding anastomotic leakage and textbook outcome. Pooled incidences were plotted for the factor-based subgroups using generalized additive models and 2-phase models. Casemix predicted outcomes were plotted and compared with observed outcomes. The investigated factors included annual volume, TMIE experience, clinic visits, courses and fellowships followed, and proctor supervision.RESULTS: This study included 2121 patients. The length of the learning curve was shorter for centers with an annual volume >50 compared to centers with an annual volume CONCLUSIONS: More efficient learning was observed in centers with higher annual volume. Visiting an expert clinic, completing a fellowship, or implementation under a proctor's supervision were not associated with more efficient learning.

Contains fulltext : 232906.pdf (Publisher’s version ) (Open Access) BACKGROUND: Preoperative differentiation between neoplastic and nonneoplastic gallbladder polyps, and the subsequent indication for cholecystectomy remains a clinical dilemma. The current 1 cm size threshold for neoplasia is unspecific. The aim of this study was to improve diagnostic work-up for gallbladder polyps using sonographic and MRI characteristics of neoplastic and nonneoplastic polyps. METHODS: A prospective, exploratory study including patients undergoing cholecystectomy for gallbladder polyp(s) was conducted. Patients underwent targeted transabdominal ultrasound (TAUS) and MRI. Outcomes were sensitivity and specificity for polyp diagnosis, and the radiological characteristics of neoplastic and nonneoplastic polyp types. Histopathology after cholecystectomy was used as reference standard. RESULTS: Histopathology demonstrated gallbladder polyps in 20/27 patients (74%): 14 cholesterol polyps, three adenomyomatosis, two adenomas and one gastric heterotopia. Sensitivity of polyp identification were 72% (routine TAUS) and 86% (targeted TAUS and MRI). Both adenomas were identified as neoplastic on targeted TAUS and MRI. Sonographic presentation as multiple, pedunculated polyps, either heterogeneous or with hyperechoic foci, or as single polyps containing cysts were limited to nonneoplastic polyps. On MRI hyperintense polyps on T1-weighted image were cholesterol polyps. An adenoma with high-grade dysplasia showed foci of decreased ADC values. We propose a checklist for polyp evaluation by targeted TAUS and a flowchart for radiological work-up of gallbladder polyps. CONCLUSIONS: The presented checklist and flowchart could aid diagnostic work-up for gallbladder polyps compared to current routine ultrasound, by elimination of nonneoplastic polyps and ultimately improve treatment decision for patients with gallbladder polyps.

An observational prospective feasibility study in which children received a tracker 2 weeks before a tonsillectomy and were required to wear it until four weeks postoperatively. The parents used a diary to log the estimated steps of their child. As primary endpoint, the compliance of complete datasets was compared between the tracker and the diary. As secondary endpoints, the agreement of steps between tracker and diary, and the recovery time after tonsillectomy were analyzed. Twenty-four patients (50% male) with a median age of 6 years were recruited. The tracker had a complete dataset compliance of 91.7% in the pre-operative and 58.3% in postoperative period, whereas the diary’s compliance was 62.5% in the pre-operative and 12.5% in the postoperative period. The difference of 29.2% and 45.8% in the pre-operative and postoperative periods between the tracker and the diary was significant (p < 0.005). The tracker and diary had a mean agreement difference of 1063 steps per day. Mean recovery time was 21 days after tonsillectomy. Conclusion: The results of this pilot study support the use of a tracker in terms of compliance and practicability. Consumer-level activity trackers are a viable alternative to conventional manual logging for clinical use in pediatric research. Trial registration: ClinicalTrials.gov Identifier: NCT03174496

Background An unhealthy lifestyle is associated with the risk of colorectal cancer (CRC), but it is unclear whether overall lifestyle after a CRC diagnosis is associated with risks of recurrence and mortality. Objectives To examine associations between postdiagnosis lifestyle and changes in lifestyle after a CRC diagnosis with risks of CRC recurrence and all-cause mortality. Methods The study population included 1425 newly diagnosed, stage I–III CRC patients from 2 prospective cohort studies enrolled between 2010 and 2016. Lifestyle, including BMI, physical activity, diet, and alcohol intake, was assessed at diagnosis and at 6 months postdiagnosis. We assigned lifestyle scores based on concordance with 2 sets of cancer prevention guidelines—from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) and the American Cancer Society (ACS)—and national disease prevention guidelines. Higher scores indicate healthier lifestyles. We computed adjusted HRs and 95% CIs using Cox regression. Results We observed 164 recurrences during a 2.8-year median follow-up and 171 deaths during a 4.4-year median follow-up. No associations were observed for CRC recurrence. A lifestyle more consistent with the ACS recommendations was associated with a lower all-cause mortality risk (HR per +1 SD, 0.85; 95% CI: 0.73–0.995). The same tendency was observed for higher WCRF/AICR (HR, 0.92; 95% CI: 0.78–1.08) and national (HR, 0.90; 95% CI: 0.77–1.05) lifestyle scores, although these associations were statistically nonsignificant. Generally, no statistically significant associations were observed for BMI, physical activity, diet, or alcohol. Improving one's lifestyle after diagnosis (+1 SD) was associated with a lower all-cause mortality risk for the ACS (HR, 0.80; 95% CI: 0.67–0.96) and national (HR, 0.84; 95% CI: 0.70–0.999) scores, yet was statistically nonsignificant for the WCRF/AICR score (HR, 0.94; 95% CI: 0.78–1.13). Conclusions A healthy lifestyle after CRC diagnosis and improvements therein were not associated with the risk of CRC recurrence, but were associated with a decreased all-cause mortality risk.

Background: The primary aim was to assess the diagnostic accuracy of routine ultrasound assessment for gallbladder polyps. The secondary aim was to identify the characteristics that differentiate neoplastic polyps from nonneoplastic polyps. Methods: A total of 156 patients with histopathologically proven gallbladder polyps in 4 Dutch hospitals between 2003 and 2013 were included. Sensitivity and specificity of ultrasound for polyp size, number of polyps, and polyp type were assessed using histopathological findings as a reference standard. In addition, diagnostic accuracy of sonographic size ≥1 cm for neoplasia was assessed. Subgroup analysis for patients with polyps as primary indication for cholecystectomy was performed. The sonographic polyp characteristics on preoperative routine ultrasound were described. Results: Fifty-six percent of gallbladder polyps were preoperatively identified on ultrasound, of which 31% were neoplastic. Sensitivity and specificity of ultrasound to estimate polyp size were 93 and 43% (subgroup; 92 and 33%). Sensitivity and specificity of sonographic polyp size ≥1 cm for neoplasia were 86 and 32% (subgroup; 94 and 26%). No specific sonographic characteristics for neoplastic polyps could be established due to lack of reporting. Conclusion: Routine ultrasound assessment of polyps is associated with overestimation of polyp size and low specificity of sonographic size ≥1 cm for neoplasia, which contributes to surgical overtreatment of nonneoplastic polyps.

Persistent human papillomavirus (HPV) infection is associated with the development of oropharyngeal squamous cell carcinoma (OPSCC), and increasing incidences of OPSCC are reported. The generally favorable treatment outcome in patients with HPV-driven OPSCC has brought de-escalation of treatment into discussion. Nevertheless, 13% to 25% develop a relapse within two years after current standard treatment. New biomarkers are urgently required to monitor therapy response, tumor burden, and minimal residual disease during follow-up. This observational study examined 50 patients with OPSCC to investigate plasma cell-free (cf) HPV-DNA derived from tumor cells before therapy and during follow-up. Real-time quantitative PCR was applied to quantify the DNA concentration of HPV oncogenes E6 and E7. A total of 85.7% of pretreatment samples from patients with HPV-driven OPSCC (n = 28) were positive for at least one marker, and cfHPV-DNA concentration increased with tumor size. Virtually no signals were detected in HPV-negative OPSCC patients (n = 20; P ≤ 0.001). Patients without clinical evidence of recurrence had significantly reduced cfHPV-DNA concentrations after therapy (P ≤ 0.001). Conversely, cfHPV-DNA levels increased or remained above threshold in five patients who had residual disease or developed recurrence. In conclusion, plasma cfHPV-DNA detection correlates with the clinical course of disease in patients with HPV-driven OPSCC. Consequently, extensive clinical investigation should be considered if cfHPV-DNA is detected during follow-up of patients with HPV-driven OPSCC.

Denne evaluering er gennemført af BUILD, Aalborg Universitet som en af fire evalueringer af forsøg med modulsystemer i tomme bygninger i fire kommuner, og som bl.a. bygger på udviklingsteamets egenevaluering af deres modulforsøg. Evalueringen er gennemført for Bolig- og Planstyrelsen (BPST).BUILD har udarbejdet en teknisk evalueringsrapport for hvert af disse forsøg i den rækkefølge, som de er blevet afsluttet:• Faxe Kommune med forsøg på 2. sal på bygning 19 på nedlagt Faxe Sygehus. • Faaborg-Midtfyn Kommune med forsøg på del af Fabers Fabrikker i Ryslinge.• Hjørring Kommune med forsøg på 1. sal på Hjørring Station i Hjørring.• Vordingborg Kommune med forsøg på nedlagt Mern Station i MernFaxe Kommune har gennemført en transformation af tom 2. sal i bygning 19 på nedlagt Faxe Sygehus. Der er indflyttet unge udsatte med behov for social støtte, men indretning kan hurtigt ændres til andre behov for billige bofællesskaber. Projektgruppen har udvikletet nyt mobilt modulsystem bestående af indervægge, køkkener og badeværelser med installationsforsyning under vægbænke.BUILD har vurderet, at forsøget er gennemført med succes, har opfyldt formålene og kan være til stor inspiration for andre modulforsøg og transformationer.​ Denne evaluering er gennemført af BUILD, Aalborg Universitet som en af fire evalueringer af forsøg med modulsystemer i tomme bygninger i fire kommuner, og som bl.a. bygger på udviklingsteamets egenevaluering af deres modulforsøg. Evalueringen er gennemført for Bolig- og Planstyrelsen (BPST).BUILD har udarbejdet en teknisk evalueringsrapport for hvert af disse forsøg i den rækkefølge, som de er blevet afsluttet:• Faxe Kommune med forsøg på 2. sal på bygning 19 på nedlagt Faxe Sygehus. • Faaborg-Midtfyn Kommune med forsøg på del af Fabers Fabrikker i Ryslinge.• Hjørring Kommune med forsøg på 1. sal på Hjørring Station i Hjørring.• Vordingborg Kommune med forsøg på nedlagt Mern Station i MernFaxe Kommune har gennemført en transformation af tom 2. sal i bygning 19 på nedlagt Faxe Sygehus. Der er indflyttet unge udsatte med behov for social støtte, men indretning kan hurtigt ændres til andre behov for billige bofællesskaber. Projektgruppen har udvikletet nyt mobilt modulsystem bestående af indervægge, køkkener og badeværelser med installationsforsyning under vægbænke.BUILD har vurderet, at forsøget er gennemført med succes, har opfyldt formålene og kan være til stor inspiration for andre modulforsøg og transformationer.​

OBJECTIVES: Programmed death-ligand 1 (PD-L1) is the only approved predictive biomarker for immunotherapy in non-small cell lung cancer (NSCLC). However, predictive PD-L1 immunohistochemistry is subject to interobserver variability. We hypothesized that a pathologist's personality influences the interobserver variability and diagnostic accuracy of PD-L1 immunoscoring.MATERIALS AND METHODS: Seventeen pathologists performed PD-L1 immunoscoring on 50 resected NSCLC tumors in three categories (RESULTS: The overall agreement among pathologists for a series of 47 tumors was substantial (kappa = 0.63). Of these, 23/47 (49%) tumors were entirely negative or largely positive, resulting in a kappa value of 0.93. The remaining 24/47 (51%) tumors had a PD-L1 score around the cutoff value, generating a kappa value of 0.32. Pathologists with high scores for conscientiousness (careful, diligent) had the least interobserver variability (r = 0.6, p = 0.009). Also, they showed a trend towards higher sensitivity (74% vs. 68%, p = 0.4), specificity (86% vs. 82%, p = 0.3) and percent agreement (83% vs. 79%, p = 0.3), although not significant. In contrast, pathologists with high scores for neuroticism (sensitive, anxious) had significantly lower specificity (80% vs. 87%, p = 0.03) and percent agreement (78% vs. 85%, p = 0.03). Also, a trend towards high interobserver variability (r = -0.3, p = 0.2) and lower sensitivity (68% vs. 74%, p = 0.3) was observed, although not significant. Pathologists with relatively high scores for conscientiousness scored fewer tumors PD-L1 positive at the ≥ 1% cut-off (r = -0.5, p = 0.03). In contrast, pathologists with relatively high scores for neuroticism score more tumors PD-L1 positive at ≥ 1% (r = 0.6, p = 0.017) and ≥ 50% cut-offs (r = 0.6, p = 0.009).CONCLUSIONS: This study is the first to demonstrate the impact of a pathologist's personality on the interobserver variability and diagnostic accuracy of immunostaining, in the context of PD-L1 in NSCLC. Larger studies are needed for validation of these findings.

Denne evaluering er gennemført af BUILD, Aalborg Universitet som en af fire evalueringer af forsøg med modulsystemer i tomme bygninger i fire kommuner, og som bl.a. bygger på udviklingsteamets egenevaluering af deres modulforsøg. Evalueringen er gennemført for Bolig- og Planstyrelsen (BPST).BUILD har udarbejdet en teknisk evalueringsrapport for hvert af disse forsøg i den rækkefølge, som de er blevet afsluttet:• Faxe Kommune med forsøg på 2. sal på bygning 19 på nedlagt Faxe Sygehus.• Faaborg-Midtfyn Kommune med forsøg på del af Fabers Fabrikker i Ryslinge.• Hjørring Kommune med forsøg på 1. sal på Hjørring Station i Hjørring.• Vordingborg Kommune med forsøg på nedlagt Mern Station i Mern.Vordingborg Kommune har gennemført renovering af bevaringsværdige stationsbygninger på nedlagt Mern Station. I modulforsøget har de desuden udviklet et fleksibelt, industrielt fremstillet modulhus på 64 m2 med 10 m2 hems, som kan demonteres for evt. flytning. De 4 lejligheder i stationsbygningen og de 2-6 modulhuse er p.t. ikke indflytningsklar, men de er egnet til forskellige beboere, som har brug for en midlertidig bolig. BUILD har vurderet, at modulforsøget har opfyldt formålene og kan være til stor inspiration for andre. Denne evaluering er gennemført af BUILD, Aalborg Universitet som en af fire evalueringer af forsøg med modulsystemer i tomme bygninger i fire kommuner, og som bl.a. bygger på udviklingsteamets egenevaluering af deres modulforsøg. Evalueringen er gennemført for Bolig- og Planstyrelsen (BPST).BUILD har udarbejdet en teknisk evalueringsrapport for hvert af disse forsøg i den rækkefølge, som de er blevet afsluttet:• Faxe Kommune med forsøg på 2. sal på bygning 19 på nedlagt Faxe Sygehus.• Faaborg-Midtfyn Kommune med forsøg på del af Fabers Fabrikker i Ryslinge.• Hjørring Kommune med forsøg på 1. sal på Hjørring Station i Hjørring.• Vordingborg Kommune med forsøg på nedlagt Mern Station i Mern.Vordingborg Kommune har gennemført renovering af bevaringsværdige stationsbygninger på nedlagt Mern Station. I modulforsøget har de desuden udviklet et fleksibelt, industrielt fremstillet modulhus på 64 m2 med 10 m2 hems, som kan demonteres for evt. flytning. De 4 lejligheder i stationsbygningen og de 2-6 modulhuse er p.t. ikke indflytningsklar, men de er egnet til forskellige beboere, som har brug for en midlertidig bolig. BUILD har vurderet, at modulforsøget har opfyldt formålene og kan være til stor inspiration for andre.

Up to 14% of large cell neuroendocrine carcinomas (LCNEC) are diagnosed in continuity with non-small cell lung carcinoma. In addition to these combined lesions, 1-7% of lung tumors present as co-primary tumors with multiple synchronous lesions. We evaluated molecular and clinicopathological characteristics of combined and co-primary LCNEC-adenocarcinoma (ADC) tumors. Ten patients with LCNEC-ADC (combined) and 5 patients with multiple synchronous ipsilateral LCNEC and ADC tumors (co-primary) were included. DNA was isolated from distinct tumor parts and 65 cancer genes were analyzed by next generation sequencing. Immunohistochemistry was performed including neuroendocrine markers, pRb, Ascl1 and Rest. Pure ADC (N=37) and LCNEC (N=17) cases were used for reference. At least 1 shared mutation, indicating tumor clonality, was found in LCNEC- and ADC-parts of 10/10 combined tumors but only in 1/5 co-primary tumors. A range of identical mutations was observed in both parts of combined tumors: 8/10 contained ADC-related (EGFR/KRAS/STK11 and/or KEAP1), 4/10 RB1 and 9/10 TP53 mutations. Loss of pRb IHC was observed in 6/10 LCNEC- and 4/10 ADC-parts. The number and intensity of expression of Ascl1 and neuroendocrine markers increased from pure ADC (low) to combined ADC (intermediate) and combined and pure LCNEC (high). The opposite was true for Rest expression. In conclusion, all combined LCNEC-ADC tumors were clonally related indicating a common origin. A relatively high frequency of pRb inactivation was observed in both LCNEC- and ADC-parts, suggesting an underlying role in LCNEC-ADC development. Furthermore, neuroendocrine differentiation might be modulated by Ascl1(+) and Rest(-) expression. This article is protected by copyright. All rights reserved.

Background Molecular tumor boards (MTBs) provide rational, genomics‐driven, patient‐tailored treatment recommendations. Worldwide, MTBs differ in terms of scope, composition, methods, and recommendations. This study aimed to assess differences in methods and agreement in treatment recommendations among MTBs from tertiary cancer referral centers in The Netherlands. Materials and Methods MTBs from all tertiary cancer referral centers in The Netherlands were invited to participate. A survey assessing scope, value, logistics, composition, decision‐making method, reporting, and registration of the MTBs was completed through on‐site interviews with members from each MTB. Targeted therapy recommendations were compared using 10 anonymized cases. Participating MTBs were asked to provide a treatment recommendation in accordance with their own methods. Agreement was based on which molecular alteration(s) was considered actionable with the next line of targeted therapy. Results Interviews with 24 members of eight MTBs revealed that all participating MTBs focused on rare or complex mutational cancer profiles, operated independently of cancer type–specific multidisciplinary teams, and consisted of at least (thoracic and/or medical) oncologists, pathologists, and clinical scientists in molecular pathology. Differences were the types of cancer discussed and the methods used to achieve a recommendation. Nevertheless, agreement among MTB recommendations, based on identified actionable molecular alteration(s), was high for the 10 evaluated cases (86%). Conclusion MTBs associated with tertiary cancer referral centers in The Netherlands are similar in setup and reach a high agreement in recommendations for rare or complex mutational cancer profiles. We propose a “Dutch MTB model” for an optimal, collaborative, and nationally aligned MTB workflow. Implications for Practice Interpretation of genomic analyses for optimal choice of target therapy for patients with cancer is becoming increasingly complex. A molecular tumor board (MTB) supports oncologists in rationalizing therapy options. However, there is no consensus on the most optimal setup for an MTB, which can affect the quality of recommendations. This study reveals that the eight MTBs associated with tertiary cancer referral centers in The Netherlands are similar in setup and reach a high agreement in recommendations for rare or complex mutational profiles. The Dutch MTB model is based on a collaborative and nationally aligned workflow with interinstitutional collaboration and data sharing., Worldwide, molecular tumor boards (MTBs) differ in terms of scope, composition, methods, and recommendations. This article assesses differences in methods and agreement in treatment recommendations among MTBs from tertiary cancer referral centers in The Netherlands.

BACKGROUND The goal of this review was to present an overview of the currently identified molecular parameters in head and neck squamous cell carcinoma (HNSCC) of nonsmokers and nondrinkers (NSND). METHODS Following the PRISMA guidelines, a systematic search was performed using the electronic databases PubMed, Embase, and Google Scholar. RESULTS Of the 902 analyzed unique studies, 74 were included in a quantitative synthesis and 24 in a meta-analysis. Human papillomavirus (HPV) was reported as a molecular parameter in 38 studies, followed by p16 and TP53 (23 and 14 studies, respectively). The variety of other molecular parameters concerned sporadic findings in small numbers of NSND. CONCLUSIONS HNSCC in NSND is more often related to HPV and p16 overexpression compared to tumors of smokers-drinkers. In a third of virus-negative tumors, TP53 mutations were detected with a mutational profile associated with aging and ultraviolet light exposure rather than to tobacco consumption.

BACKGROUND: The LIR!C trial showed that laparoscopic ileocaecal resection is a cost-effective treatment that has similar quality-of-life outcomes to treatment with infliximab, an anti-tumour necrosis factor (TNF) drug. We aimed to compare long-term outcomes of both interventions and identify baseline factors associated with the duration of treatment effect in each group.METHODS: In this retrospective follow-up study, we collected data from patients who participated in the LIR!C trial, a multicentre randomised controlled trial that compared quality of life after surgical resection versus infliximab in adult patients with non-stricturing and immunomodulator-refractory ileocaecal Crohn's disease. From Jan 1 to May 1, 2018, we collected follow-up data from the time from enrolment in the LIR!C trial until the last visit at either the gastrointestinal surgeon or gastroenterologist. In this study, outcomes of interest were need for surgery or repeat surgery or anti-TNF therapy, duration of treatment effect, and identification of factors associated with the duration of treatment effect. Duration of treatment effect was defined as the time without need for additional Crohn's disease-related treatment (corticosteroids, immunomodulators, biologics, or surgery).FINDINGS: We collected long-term follow-up data for 134 (94%) of 143 patients included in the LIR!C trial, of whom 69 were in the resection group and 65 were in the infliximab group. Median follow-up was 63·5 months (IQR 39·0-94·5). In the resection group, 18 (26%) of 69 patients started anti-TNF therapy and none required a second resection. 29 (42%) patients in the resection group did not require additional Crohn's disease-related medication, although 14 (48%) of these patients were given prophylactic immunomodulator therapy. In the infliximab group, 31 (48%) of 65 patients had a Crohn's disease-related resection, and the remaining 34 patients maintained, switched, or escalated their anti-TNF therapy. Duration of treatment effect was similar in both groups, with a median time without additional Crohn's disease-related treatment of 33·0 months (95% CI 15·1-50·9) in the resection group and 34·0 months (0·0-69·3) in the infliximab group (log-rank p=0·52). In both groups, therapy with an immunomodulator, in addition to the allocated treatment, was associated with duration of treatment effect (hazard ratio for resection group 0·34 [95% CI 0·16-0·69] and for infliximab group 0·49 [0·26-0·93]).INTERPRETATION: These findings further support laparoscopic ileocaecal resection as a treatment option in patients with Crohn's disease with limited (affected segment ≤40 cm) and predominantly inflammatory terminal ileitis for whom conventional treatment is not successful.FUNDING: None.

The ice microstructure in the lower part of the North Greenland Eemian Ice Drilling (NEEM) ice core consists of relatively fine-grained ice with a single maximum crystallographic preferred orientation (CPO) alternated by much coarser-grained ice with a partial (great circle) girdle or multi-maxima CPO. In this study, the grain-size-sensitive (GSS) composite flow law of Goldsby and Kohlstedt (2001) was used to study the effects of grain size and premelting (liquid-like layer along the grain boundaries) on strain rate in the lower part of the NEEM ice core. The results show that the strain rates predicted in the fine-grained layers are about an order of magnitude higher than in the much coarser-grained layers. The dominant deformation mechanisms, based on the flow relation of Goldsby and Kohlstedt (2001), between the layers is also different, with basal slip rate limited by grain boundary sliding (GBS-limited creep) being the dominant deformation mechanism in the finer-grained layers, while GBS-limited creep and dislocation creep (basal slip rate limited by non-basal slip) contribute both roughly equally to bulk strain in the coarse-grained layers. Due to the large difference in microstructure between finer-grained ice and the coarse-grained ice at premelting temperatures (T>262 K), it is expected that the fine-grained layers deform at high strain rates, while the coarse-grained layers are relatively stagnant. The difference in microstructure, and consequently in viscosity, between impurity-rich and low-impurity ice can have important consequences for ice dynamics close to the bedrock.