Pancreas Cancer Learning Health Network Established to Share Best Practice Across 14 Centers and Improve Patient Outcomes

PURPOSE/OBJECTIVE(S)

Pancreas cancer (PC) survival is among the lowest of all malignancies. Clinical trials have failed to significantly improve outcomes. Individual and institutional biases in care result in significant variation in practice, further hindering progress. Learning health networks (LHNs) prospectively collect real world data across centers and test improvements that can rapidly be expanded across centers if deemed successful. Herein, we report preliminary progress from the Pancreas Cancer Canopy Cancer Collective (PC-CCC), the first oncology LHN, established to improve duration and quality of survival in PC.

MATERIALS/METHODS

In 2019, we established the PC-CCC with six care centers who engaged in a collaborative design process to create a set of improvement aims, change ideas, and outcome measures. Center team members receive training and coaching in collaborative quality improvement methods, applied to local improvement efforts. Eight more centers joined in 2021, and a shared Canopy outcomes database was built and implemented to inform center-specific and network-wide improvement efforts and allow the LHN to undertake research using real-world data. Current improvement efforts are focused on proactively screening new PC patients for: (1) Clinical trials, (2) pancreas enzymes, (3) palliative care needs, and (4) goals of care conversations.

RESULTS

Currently, 14 care centers are active participants in the PC-CCC LHN. Data on a total of 2,002 PC patients are available to date. At presentation to the care center, most patients are female (51%) and have biopsy proven PC (83.9%). Average age is 68 years, and presenting disease status is metastatic (14.5%), resectable (11.4%), locally advanced (10.9%), borderline resectable (8.1%), or not yet staged (40%). For those who received radiation, 75.8% received stereotactic body radiation therapy. Among patients whose chemotherapy regimen was documented, most received 5-fluorouracilbased treatment (52%). Descriptive follow up data (including treatment and outcomes) are being actively updated, to be reported at time of presentation.

CONCLUSION

Creation of a cancer LHN for PC is feasible and has set the stage for improving patient and provider outcomes through iterative community-building, continuous improvement, and sharing of data and multidisciplinary best practices. Additionally, the data obtained from the CCC database can rapidly inform the network how variation in clinical practice across centers can influence outcomes.

Promoting resilience in healthcare workers during the COVID-19 pandemic with a brief online intervention

INTRODUCTION

The psychological wellbeing of healthcare workers has been impacted by the high levels of stress many have experienced during the Coronavirus Disease 2019 (COVID-19) pandemic. This study aimed to examine the feasibility and acceptability of a brief online course focused on introducing evidence-based skills that could increase resilience and decreases emotional distress in healthcare workers during the pandemic.

MATERIALS AND METHODS

Employees of a large healthcare system completed a mental health survey at baseline, and then one month and two months after some employees participated in an online resilience-enhancement course consisting of three 12-19 min videos focused on mindfulness, mentalization, and self-compassion.

RESULTS

A total of 554 participants completed the baseline survey, endorsing moderate to high levels of emotional distress. Of those who completed all three assessments and participated in the course (n = 38), significant improvements in resilience and reductions in emotional distress were found one and two months later, in comparison to those who did not participate in the course (n = 110).

DISCUSSION

These findings suggest that a brief, online intervention can improve the mental health of healthcare workers during a crisis such as the COVID-19 pandemic.

POS0366 PRO-INFLAMMATORY EFFECTS OF HUMAN APATITE CRYSTALS EXTRACTED FROM PATIENTS SUFFERING FROM CALCIFIC TENDINOPATHY

Background:

Calcific tendonitis of the rotator cuff is due to carbonated apatite deposits in the shoulder tendons. During the evolution of the disease, an acute inflammatory episode may occur leading to the disappearance of the calcification. Although hydroxyapatite crystals-induced inflammation has been previously studied with synthetic crystals, no data are available with calcifications extracted from patients suffering from calcific tendinopathy. The objective of the study was to explore the inflammatory properties of human calcifications and the pathways involved.

Objectives:

The objective of the study was to explore the inflammatory properties of human calcifications and the pathways involved.

Methods:

Human calcifications were obtained from patients treated for their shoulder pain related to a calcific tendinopathy of the rotator cuff. Calcifications were extracted by ultrasound-guided lavage and aspiration as previously described [1]. Human calcifications and synthetic hydroxyapatite (sHA) were used in vitro to stimulate human monocytes and macrophages, the human myeloid cell line THP-1 and human tenocytes. The release of IL-1β, IL-6 and IL-8 by cells was quantified by ELISA. Gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR. NF-kB activation and NLRP3 involvement was assessed in THP-1 cells using a NF-kB inhibitor and a Caspase 1 inhibitor. The inflammatory properties were then assessed in vivo using a mouse air pouch model. The membrane thickness and infiltrate were assessed 6 and 24 hours after the injection of human calcifications or synthetic hydroxyapatite using hematoxylin and eosin staining. Macrophages, neutrophils and lymphocytes infiltrates were assessed by immunohistochemistry. Total RNA was extracted from the membranes and expression of IL-1β, IL-6 and TNFβ was quantified by PCR.

Results:

Human calcifications were able to induce a significant release of IL-1β when incubated with monocytes, macrophages and THP-1 only if they were first primed with LPS (lipopolysaccharide) for monocytes and macrophages or PMA (Phorbol 12-myristate 13-acetate) for THP-1. No IL-1β was detected in tenocytes’ supernatants. Stimulation of THP-1 by human calcifications led to similar levels of IL-1β when compared to synthetic hydroxyapatite although these levels were significantly inferior in monocytes and macrophages. IL-6 and IL-8 levels were not increased in the supernatants after crystal stimulation. Patient’s crystals enhanced mRNA expression of pro-IL-1β, as well as IL-18, NF-kB and TGFβ when IL-6 and TNFα expression were not. IL-1β production was reduced by the inhibition NF-kB as well as Caspase 1 indicating the role of NLRP3 inflammasome. In vivo, injection of human calcifications or synthetic hydroxyapatite in air pouch led to significant increase in membrane thickness with an infiltrate mainly composed of macrophages. Significant overexpression of IL-1β was only observed in the synthetic hydroxyapatite group.

Conclusion:

As synthetic hydroxyapatite, human calcifications were able to induce an inflammatory response resulting in the production of IL-1β after NF-kB activation and through NLRP3 inflammasome. In some experiments, IL-1β induction was lower with human calcifications compared to synthetic apatite. Differences in size, shape and protein content may explain this observation.

References:

[1]Darrieutort-Laffite C, Arnolfo P, Garraud T, Adrait A, Couté Y, Louarn G, et al. Rotator Cuff Tenocytes Differentiate into Hypertrophic Chondrocyte-Like Cells to Produce Calcium Deposits in an Alkaline Phosphatase-Dependent Manner. J Clin Med. 2019 Sep 26;8(10):1544. doi: 10.3390/jcm8101544.

Acknowledgements:

Fondation Arthritis, Recherche et Rhumatismes and French Society for Rheumatology for their financial support

Disclosure of Interests:

None declared

A randomized controlled clinical trial on the effect of acupuncture therapy in dairy cows affected by pyometra

Pyometra (PYO) is a reproductive disease characterized by the accumulation of purulent or mucopurulent material within the uterine lumen, in the presence of an active corpus luteum (CL). As the CL continues secreting progesterone, PYO would develop following endometritis. Due to prohibited use of artificial luteolytic hormones in US certified organic dairies, conventional therapies consisting of administration of prostaglandin F2α, are not applicable. The objective of this study was to evaluate the efficacy of two acupuncture procedures on the treatment of persistent CL in cows with PYO. We hypothesized that acupuncture would reduce CL diameter and serum progesterone (P4) concentrations, leading to regression of PYO. Holstein cows with PYO, at an USDA certified organic dairy farm in Northern Colorado, were enrolled in a randomized controlled clinical trial and assigned to 1 of 3 treatments: (1) control pyometra (CP; no treatment; n = 17); (2) electroacupuncture (EAP; n = 15); and (3) laser acupuncture (LAP; n = 15). Each cow received three 9-min (EAP) or 20-min (LAP) acupuncture sessions in alternate days. All study cows had blood samples collected for determination of serum progesterone concentration at d0, and at d2, d4, d11, d18, and d25 after first treatment. The ovaries were scanned by transrectal ultrasonography at -3d, d0, d2, d4, d11, and d18 to determine the diameter of the CL. The effect of treatment in the outcome variables was evaluated by ANOVA and by repeated measures analyses, accounting for baseline data (CL diameter and progesterone serum concentration). Average ± SE change in CL diameter from d0 to d18 were 0.94 ± 1.0 mm, 0 ± 1.0 mm, and - 0.33 ± 1.0 mm for CP, EAP, and LAP, respectively. The repeated measures analysis indicated no significant differences for CL diameter among groups. None of the study cows had serum progesterone values <1 ng/ml by the end of the monitoring period (d25) and average ± SE change from d0 to d25 were - 4.0 ± 1.97 ng/ml, -0.76 ± 2.1 ng/ml, and 3.24 ± 1.9 ng/ml for CP, EAP, and LAP, respectively. The repeated measures analysis indicated no significant differences for serum progesterone concentrations among groups. On farm cow records reviewed 150 d after treatment indicated that 2 cows in EAP and 1 cow in LAP conceived 38 d, 68 d, and 38 d, after treatment completion. In conclusion, acupuncture was not an effective treatment for persistent CL in cows with PYO, during the monitoring period.

Abstract CT065: A Phase I clinical trial: Use of 4-demethyl-4-cholesteryl- oxycarbonyl-penclomedine (DM-CHOC-PEN) plus radiation as treatments for cancers involving the CNS

Purpose: 4-Demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) is a poly-chlorinated pyridine cholesteryl carbonate with a MOA via bis-alkylation of DNA @ N7-guanine and N4-cytosine that has completed Phase II studies [AACR, #CT129, 2017] in subjects with cancers involving the CNS. Four (4) subjects in the Phase I/II trials required surgery for persistent CNS lesions following DM-CHOC-PEN therapy with 39-98.8 mg/m2 of drug. DM-CHOC-PEN was identified in samples from all 4-subjects - 90-212 ng/g tumor. Thus, the drug penetrates the CNS and tumors and is available to act as a radiosensitizer; the latter has been supported with in vitro studies [AACR, #4746, 2017]. The current presentation reviews Phase I clinical data that supports the safety, dose-tolerance and use for DM-CHOC-PEN plus radiation in subjects with cancers involving the CNS - IND 68,876.

Patients & Methods: DM-CHOC-PEN was administered as a 3-hr IV infusion once to subjects with advanced cancer involving the CNS. A single dose (39 mg/m2 to 98.7 mg/m2 in escalating Phase I scheme) was administered once 3-weeks prior to receiving stereotaxic radio-surgery (SRS), gamma knife or whole brain irradiation (WBRT) therapy. Radiation was administered in doses of 15-30 Gy depending on the size and number of lesions.

Results: Thirteen (13) subjects with cancer involving the CNS have been treated to date with DM-CHOC-PEN (6-NSCLC, 1-breast, 1-melanoma, 2-GBM & 3-sarcomas). Subjects received 39, 50, 70, 86.8 or 98.7 mg/m2 and 15-30 Gy of radiation. The drug/radiation combination was well tolerated. One (1) subject with NSCLC did develop vasogenic edema and tumor necrosis which resolved and the subject is in complete remission 42+ mos. A second subject with a recurrent GBM with confusion progressed - Gr-3. Ten (10) of the thirteen (13) subjects have had objective results (OS 8-54+ mos.) Bioavailability for DM-CHOC-PEN revealed a rebound phenomenon @ ~ 50 hours post-infusion with a T-release of 26.7 h. The same phenomenon was observed with RBCs (estimation using Monolix 3.2). DM-CHOC-PEN was detected bound to RBCs for 3-days (after 70 mg/m2) and was also detected in the urine (Cmax=17.5 µg/mL) until day 15. The AUC was linear for all doses. Pre-clinical radiosensitization in vitro studies [AACR #1917, 2017] support the present trial study result. Photon induced charge transfer reactions with DM-CHOC-PEN will be discussed as a MOA.

Conclusion: Data is presented that documents effectiveness and safety of DM-CHOC-PEN plus radiation as therapy for subjects with cancers involving the CNS. Observations during Phase I/II clinical trials with DM-CHOC-PEN alone supported the drug’s persistent presence in human tumors after systemic administration and possible positive effects on response to subsequent radiation. Complete data on subject responses and observed toxicities will be presented. Supported by - NCI/SBIR grants - R43 CA213545-02 and NIH NIGMS 1 U54 GM104940 - the latter funds the Louisiana Clinical and Translational Science Center.

Citation Format: RS Weiner, T Mahmood, Lee Roy Morgan, K. Harris, A. Baghian, SJ DiBiase, P. Friedlander, ML Ware, R. Kawauchi, J. Herman, M. Bhandari. A Phase I clinical trial: Use of 4-demethyl-4-cholesteryl- oxycarbonyl-penclomedine (DM-CHOC-PEN) plus radiation as treatments for cancers involving the CNS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT065.

Abstract CT119: Early phase I clinical trial results for 4-demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) plus radiation in cancers involving the CNS

Purpose:4-Demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) is a poly-chlorinated pyridine cholesteryl carbonate with a mechanism of action (MOA) via bis-alkylation of DNA @ N7-guanine and N4-cytosine that has completed Phase I/II studies [AACR, 58, #CT129, 2017] in subjects with cancers involving the CNS. Four (4) subjects in the Phase I/II trials required surgery for persistent CNS lesions following DM-CHOC-PEN therapy and DM-CHOC-PEN was identified in samples from all 4-subjects - 90-212 ng/g tumor [subjects had been treated with 39-98.8 mg/m2 of drug]. Thus, the drug penetrates the CNS and concentrates in tumors. It is available, therefore, to act as a radiosensitizer as demonstrated in in vitro studies [AACR, 58, #4746, 2017]. The current presentation reviews Phase I clinical data that supports the safety, dose-tolerance, and use of DM-CHOC-PEN with radiation in subjects with cancers involving the CNS - IND 68,876.

Patients & Methods: DM-CHOC-PEN was administered as a 3-hr IV infusion once every 21 days to subjects with advanced cancer involving the CNS. A single dose was administered prior to standard radiation therapy. The dose was escalated from 39 mg/m2 to 98.7 mg/m2 I.X1, then 3-weeks later the subject received stereotaxic radio-surgery (SRS) or whole brain irradiation (WBRT). Total radiation administered was 15-30 Gy depending on the size and number of lesions.

Results: Nine (9) subjects with cancer involving the CNS have been treated to date - (6-NSCLC, 1-breast, 1-melanoma & 1-sarcoma). Subjects received 39, 55, 70, 86.8 or 98.7 mg/m2 followed by 15-30 Gy of radiation. The drug/radiation combination was well tolerated. One (1) subject with NSCLC developed vasogenic edema and tumor necrosis which resolved; that subject is in complete remission 31+ mos. Six out of nine subjects have had objective responses (OS 4 - 42+ mos.) Bioavailability for DM-CHOC-PEN revealed a rebound phenomenon @ ~ 50 hours post-infusion with a T-release of 26.7 h. The same phenomenon was observed with RBCs (estimation using Monolix 3.2). DM-CHOC-PEN was detected bound to RBCs for 3-days (after 70 mg/m2); DM-CHOC-PEN was also detected in the urine (Cmax=17.5 µg/mL) until day 15. The AUC was linear for all doses. Pre-clinical in vitro studies supported the clinical data: NSCLC cells treated with DM-CHOC-PEN (0.1 -1.0 µg/mL) demonstrated 50 & 100% cytotoxicity @ 0.4 & 1.0 µg/mL. For radiation alone (6, 9 &12 Gy) - cell kill was 20 & 65% @ 6 & 12 Gy [100% kill was not observed at this dose range]; for DM-CHOC-PEN (0.25 µg/mL) plus radiation (6-12 Gy) - cell kill was 80 & 100% @ 6 & 12 Gy. Photon induced charge transfer reactions with DM-CHOC-PEN will be discussed.

Conclusion: Preliminary data is presented that supports enhanced cytotoxicity and safety of DM-CHOC-PEN plus radiation as therapy for subjects with cancers involving the CNS. Observations during Phase I/II clinical trials with DM-CHOC-PEN alone support the drug's persistent presence in human tumors after systemic administration and possible positive effects on response to subsequent radiation. Complete data on subject responses and observed toxicities will be presented. Supported by - NCI/SBIR grants - R43 CA213545-01 and NIH NIGMS 1 U54 GM104940 - the latter funds the Louisiana Clinical and Translational Science Center.

Citation Format: LR Morgan, T Mahmood, R S. Weiner, R Kawauchi, M Bhandari, K Devisitty, J Herman, R Summe, ML Ware, P Friedlander, AH Rodgers. Early phase I clinical trial results for 4-demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) plus radiation in cancers involving the CNS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT119.

The Edinburgh visual gait score - The minimal clinically important difference

OBJECTIVE

The primary aim was to define the minimal clinically important difference (MCID) of the Edinburgh Visual Gait Score (EVGS) using correlations with the Gross Motor Function Classification System (GMFCS) and the Functional Assessment Questionnaire (FAQ). The secondary aim was to confirm the numerical value of the MCID in the Gait Profile Score (GPS).

METHOD

The EVGS and GPS scores for 151 patients with diplegic cerebral palsy (GMFCS Levels I-III) were retrospectively identified from a database held at the study centre. One-hundred and forty-one patients had FAQ data available.

RESULTS

The EVGS and GPS correlated with increasing GMFCS level (p<0.001) and FAQ score (p<0.001). A gradient of 3.8 (2.9-4.7) for the EVGS and 2.9 (2.1-3.7) for the GPS corresponded to a one-level change in GMFCS level. A gradient of 1.9 (1.3-2.4) for EVGS and 1.5 (1.1-2.0) for GPS corresponded to a one-point change in FAQ.

CONCLUSIONS

The authors propose an MCID value of 2.4 for the EVGS; representing the improvement in gait score after surgery that is likely to reflect a clinical improvement in function. This MCID is closely related to other studies defining post-operative improvements in kinematic data (GPS) and may offer guidance to post-surgical changes that might reasonably be expected to either improve or prevent deteriorating function.

A cohort study of tibialis anterior tendon shortening in combination with calf muscle lengthening in spastic equinus in cerebral palsy

The aim of this study was to evaluate the outcome of combined tibialis anterior tendon shortening (TATS) and calf muscle-tendon lengthening (CMTL) in spastic equinus. Prospectively collected data was analysed in 26 patients with hemiplegic (n=13) and diplegic (n=13) cerebral palsy (CP) (GMFCS level I or II, 14 males, 12 females, age range 10-35 years; mean 16.8 years). All patients had pre-operative 3D gait analysis and a further analysis at a mean of 17.1 months (±5.6months) after surgery. None was lost to follow-up. Twenty-eight combined TATS and CMTL were undertaken and 19 patients had additional synchronous multilevel surgery. At follow-up 79% of patients had improved foot positioning at initial contact, whilst 68% reported improved fitting or reduced requirement of orthotic support. Statistically significant improvements were seen in the Movement Analysis Profile for ankle dorsi-/plantarflexion (4.15°, p=0.032), maximum ankle dorsiflexion during swing phase (11.68°, p<0.001), and Edinburgh Visual Gait Score (EVGS) (4.85, p=0.014). Diplegic patients had a greater improvement in the EVGS than hemiplegics (6.27 -vs- 2.21, p=0.024). The originators of combined TATS and CMTL showed that it improved foot positioning during gait. The present study has independently confirmed favourable outcomes in a similar patient population and added additional outcome measures, the EVGS, foot positioning at initial contact, and maximum ankle dorsiflexion during swing phase. Study limitations include short term follow-up in a heterogeneous population and that 19 patients had additional surgery. TATS combined with CMTL is a recommended option for spastic equinus in ambulatory patients with CP.

Using a goal attainment scale in the evaluation of outcomes in patients with diplegic cerebral palsy

A goal attainment scale (GAS) was used to evaluate outcomes of surgical and non-surgical interventions to improve gait in 45 children with diplegic cerebral palsy. Personal goals were recorded during pre-intervention gait analysis in two groups. Twenty children underwent orthopaedic surgery (Group 1) and 25 children received a non-operative intervention (Group 2). Children and/or their carers were contacted post-intervention by telephone to complete a GAS questionnaire, rating the achievement of goals on a 5-point scale. The goals were similar in both groups. The composite GAS was transformed into a standardised measure (T-score) for each patient. Both groups on average achieved their goals (mean T-score for Group 2 was 56.3, versus 47.1 for Group 1). The difference between these two means was significant (p=0.010). Additionally, 16 children had undergone a follow-up gait analysis during the study period, but the relationship between their Gait Profile Score and GAS was not statistically significant. Both surgical and non-surgical interventions enabled children to achieve their goals, although Group 1 reported higher achievements. The GAS reflects patient's/parent's/carer's aspirations and may be as relevant as post-intervention kinematic or kinetic outcomes.

Development of recombinant stable house dust mite allergen Der p 3 molecules for component-resolved diagnosis and specific immunotherapy

BACKGROUND

The allergen Der p 3 is underrepresented in house dust mite (HDM) extracts probably due to autolysis. Recombinant stable molecule of the allergen is thus needed to improve the diagnosis of allergy and the safety and efficacy of immunotherapy.

OBJECTIVE

The current study reports the immunological characterization of two recombinant molecules of the HDM allergen Der p 3 as useful tools for diagnosis and immunotherapy.

METHODS

Recombinant mature (rDer p 3) and immature (proDer p 3) Der p 3 and their corresponding S196A mutants were produced in Pichia pastoris and purified. The stability, IgE-binding capacity and allergenicity of the different proteins were analysed and compared with those of the major mite allergen Der p 1 used as a reference. Additionally, the immunogenicity of the different allergens was evaluated in a murine model of Der p 3 sensitization.

RESULTS

Compared to the IgE reactivity to recombinant and natural Der p 3 (nDer p 3), the mean IgE binding of patient's sera to rDer p 3-S196A (50%) was higher. The poorly binding to nDer p 3 or rDer p 3 was due to autolysis of the allergen. Contrary to Der p 3, proDer p 3 displayed very weak IgE reactivity, as measured by sandwich ELISA and competitive inhibition, rat basophil leukaemia degranulation and human basophil activation assays. Moreover, proDer p 3 induced a TH 1-biased immune response that prevented allergic response in mice but retained Der p 3-specific T-cell reactivity.

CONCLUSION

rDer p 3-S196A should be used for the diagnosis of HDM allergy elicited by Der p 3, and proDer p 3 may represent a hypoallergen of Der p 3.

The relationship between the Edinburgh Visual Gait Score, the Gait Profile Score and GMFCS levels I-III

OBJECTIVE

To determine the relationship between the Edinburgh Visual Gait Score (EVGS) and the Gait Profile Score (GPS).

METHOD

Three dimensional gait data and EVGS scores from 151 diplegic children (Gross Motor Function Classification System (GMFCS) levels I-III) were used for analysis.

RESULTS

The EVGS correlated strongly with GPS (r=0.816). There was a significant difference in both gait scores between each level of the GMFCS.

CONCLUSIONS

The strong correlation of GPS with EVGS implies that any advantages of using GPS can also be applied to centres without 3-dimensional gait analysis facilities if the EVGS is used.

Recurrent varicose veins: causes and neovascularisation. A 17-year experience

AIM

The aim of the paper was to determine the causes of varicose vein recurrence and, when neovascularisation is suspected, to confirm or exclude its presence and to establish its contribution to the recurrence of varicose veins.

METHODS

A retrospective analysis of a set of 217 legs reoperated in our department over a period of 17 years with a two-year prospective histological and histochemical (nestin) analysis of resected veins.

RESULTS

Reflux as a cause of varicose vein recurrence was identified in 93% of the limbs. It was most commonly found in the area of the saphenofemoral junction, followed by the area of the saphenopopliteal junction. Reflux in the perforating veins was almost invariably linked to that in the saphenofemoral junction or saphenopopliteal junction; an isolated damage to the perforating veins was only present in three limbs. Histological and histochemical analysis was performed for the samples of eleven veins in which neovascularisation was suspected based on preoperative duplex ultrasonography evaluation. Neovascularisation was confirmed in none of these veins and none of them was the cause of recurrence.

CONCLUSION

The major cause of varicose vein recurrence is a reflux left unresolved during the primary surgery, particularly in the area of the saphenofemoral junction. A less common cause is progression of the disease and the occurrence of a new reflux. Neovascularisation is of no importance for the recurrence of varicose veins.

Estimating surface NO2 and SO2 mixing ratios from fast-response total column observations and potential application to geostationary missions

Total-column nitrogen dioxide (NO₂) data collected by a ground-based sun-tracking spectrometer system (Pandora) and an photolytic-converter-based in-situ instrument collocated at NASA's Langley Research Center in Hampton, Virginia were analyzed to study the relationship between total-column and surface NO₂ measurements. The measurements span more than a year and cover all seasons. Surface mixing ratios are estimated via application of a planetary boundary-layer (PBL) height correction factor. This PBL correction factor effectively corrects for boundary-layer variability throughout the day, and accounts for up to ≈75 % of the variability between the NO₂ data sets. Previous studies have made monthly and seasonal comparisons of column/surface data, which has shown generally good agreement over these long average times. In the current analysis comparisons of column densities averaged over 90 s and 1 h are made. Applicability of this technique to sulfur dioxide (SO₂) is briefly explored. The SO₂ correlation is improved by excluding conditions where surface levels are considered background. The analysis is extended to data from the July 2011 DISCOVER-AQ mission over the greater Baltimore, MD area to examine the method's performance in more-polluted urban conditions where NO₂ concentrations are typically much higher.