Abstract 354: Mucinous phenotype is associated with response to neoadjuvant chemotherapy in microsatellite instable resectable gastric cancer

Background: Epstein-Barr virus positivity (EBV+) and microsatellite instability (MSI-high) have been shown to be positive prognostic factors for long term survival in resectable gastric cancer (GC) in several studies. However, the benefit of perioperative treatment in patients with MSI-high tumors remains topic of discussion. Here, we present the clinicopathological outcome of patients with EBV+ and MSI-high GCs treated with surgery only in the Dutch D1/D2 trial, and treated with chemotherapy or chemoradiotherapy after preoperative chemotherapy and surgery in the CRITICS trial.

Patients and methods: EBV was determined in tumor tissue using EBV-encoded RNA in situ hybridization (EBER-ISH). PCR and/or immunohistochemistry were performed to determine MSI status. Results were correlated to histopathological response, morphological tumor characteristics and survival.

Results: In the Dutch D1/D2 trial 10.5% (47/447) of tumors were EBV+ and 10.5% (47/447) were MSI-high. In the CRITICS trial 5.5% (25/451) of tumors were EBV+ and 5.5% (25/451) were MSI-high tumors. In the Dutch D1/D2 trial, five-year overall survival probability was 51.1% for EBV+, 46.8% for MSI-high, and 42.5% for EBV-/MSS (P=0.19). In the CRITICS trial, five-year overall survival was 56.0% for EBV+, 47.3% for MSI-high, and 36.5% for EBV-/MSS (P=0.22). In the CRITICS trial, 3 (12.5%) MSI-high tumors showed moderate to complete histopathological response. Interestingly, all three showed a mucinous phenotype. Eight (36.4%) EBV+ and 114 (29.9%) EBV-/MSS tumors showed moderate to complete histopathological response. None of the EBV+ GCs showed mucinous differentiation.

Conclusions: The favorable outcome of GC patients with resectable EBV+ or MSI-high tumors compared to EBV-/MSS tumors remains after perioperative chemotherapy. In MSI-high tumors significant histopathological response to neoadjuvant chemotherapy was found only in those with a mucinous phenotype.

Citation Format: H.D. Biesma, A.T.T.D. Soeratram, K. Sikorska, I.A. Caspers, H.F. van Essen, J.M.P. Egthuijsen, A. Mookhoek, D.M. Hoek, W. Vos, H.W.M. van Laarhoven, M. Nordsmark, D.L. van der Peet, F.A.R.M. Warmerdam, M.M. Geenen, O.J.L. Loosveld, J.E.A. Portielje, M. Los, E. Meershoek - Klein Kranenbarg, H.H. Hartgrink, J. van Sandick, C.J.H. van de Velde, M. Verheij, A. Cats, B. Ylstra, N.C.T. van Grieken, On behalf of the CRITICS investigators. Mucinous phenotype is associated with response to neoadjuvant chemotherapy in microsatellite instable resectable gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 354.

Toxocara and Ascaris seropositivity among patients suspected of visceral and ocular larva migrans in the Netherlands: trends from 1998 to 2009

Toxocara canis, Toxocara cati and Ascaris suum are roundworms of dogs, cats and pigs, respectively, that can also infect humans. These zoonotic helminths have a worldwide distribution and are also endemic in the Netherlands. Infection with Toxocara sp. may result in visceral larva migrans (VLM) or ocular larva migrans (OLM) caused by the migrating larvae. Although A. suum has been reported to occasionally mature to the adult stage in humans, clinical cases of VLM suspected to be caused by A. suum have been described. Diagnosis of these helminth infections relies mainly on serology. Here we analyse the results from the Toxocara and Ascaris IgG-ELISA from a total of 2,838 serum samples from VLM and OLM suspected patients that were sent to our institution from 1998 to 2009. Results indicate that for each year the Ascaris seropositivity is significantly higher compared to the Toxocara seropositivity. Furthermore, while Toxocara seropositivity has decreased over time, the Ascaris seropositivity has not significantly changed for the past 12 years. The Ascaris and Toxocara seropositivity was also shown to increases with age and, while gender has no influence on the Ascaris seropositivity, males showed higher Toxocara seropositivity.

Prevalence of antibodies against Ascaris suum and its association with allergic manifestations in 4-year-old children in The Netherlands: the PIAMA birth cohort study

The association between helminth infections and childhood atopic diseases remains controversial. The majority of studies have been carried out in tropical areas, whereas less information is available from western countries with low intensity of helminth infections. In the Netherlands, the infection of pigs with Ascaris suum is very common, particularly on pig farms with outdoor facilities. This helminth can also infect humans, causing visceral larva migrans. This study aims at determining the prevalence of antibodies against A. suum and its association with allergic symptoms and sensitisation in a population of 4-year-old children living in The Netherlands. Blood samples from 629 children from the prospective birth cohort Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study were examined for Ascaris antibodies. Data on allergic symptoms and sensitisation were collected using questionnaires and radioallergosorbent tests (RAST). A total of 45 out of 629 (7%) were found to be Ascaris-seropositive. In addition, a positive association between Ascaris seropositivity and wheeze in the last year, doctor-diagnosed asthma and food and aero-allergen sensitisation was found. These results support the hypothesis that low-level or transient infection with helminths enhances allergic reactivity.

Co-operative learning processes of students: a longitudinal multilevel perspective

BACKGROUND

This article describes the outcomes of a longitudinal, multilevel observational study in which the relationship between the processes of co-operation and giving explanations was compared between classes trained in communication skills and classes that were untrained.

AIMS

This study examined the effects of training in basic communication skills on the processes of co-operation and giving explanation in co-operative groups. In particular, the study investigated: (a) How the processes of co-operation and giving explanations develop over time; (b) How the underlying processes of co-operation and giving explanations are related; (c) Which factors at the student and class level facilitate or hinder these processes.

SAMPLE

The study involved 192, Year 6 primary school children (mean age = 134.3 months) who worked in four-person, mixed ability, gender-balanced groups on a social studies unit of work for 12 weeks.

RESULTS

The students in the trained classes were more co-operative and gave more explanations to each other than their peers in the untrained classes. Giving solicited explanations could be traced back to co-operation and this process was enhanced by ability. In other words, the higher the individual ability levels of the students, the more co-operation was transformed into giving solicited explanations. Furthermore, over and above the effects of student ability, the higher the class' ability level, the more explanations the students gave.

CONCLUSION

The results of this study are useful in explaining why high-ability students benefit more from co-operative learning than low-ability students and why solicited explanations are more effective than unsolicited explanations. By opening the black box of co-operative learning, our analysis enables us to attribute the effects of co-operative learning to peer interactions with more able peers and this is promoted by class ability level. These factors have been mentioned in the literature as a possible explanation of 'contextual effects' but not investigated empirically.