Immigration Status and Breast Cancer Surgery Quality of Care Metrics: A Population-Level Analysis

INTRODUCTION

As immigrant women face challenges accessing health care, we hypothesized that immigration status would be associated with fewer women with breast cancer receiving surgery for curable disease, fewer undergoing breast conserving surgery (BCS), and longer wait time to surgery.

METHODS

A population-level retrospective cohort study, including women aged 18-70 years with Stage I-III breast cancer diagnosed between 2010 and 2016 in Ontario was conducted. Multivariable analysis was performed to assess odds of undergoing surgery, receiving BCS and wait time to surgery.

RESULTS

A total of 31,755 patients were included [26,253 (82.7%) Canadian-born and 5502 (17.3%) immigrant women]. Immigrant women were younger (mean age 51.6 vs. 56.1 years) and less often presented with Stage I/II disease (87.4% vs. 89.8%) (both p < .001). On multivariable analysis, there was no difference between immigrant women and Canadian-born women in odds of undergoing surgery [Stage I OR 0.93 (95% CI 0.79-1.11), Stage II 1.04 (0.89-1.22), Stage III 1.22 (0.94-1.57)], receiving BCS [Stage I 0.93 (0.82-1.05), Stage II 0.96 (0.86-1.07), Stage III 1.00 (0.83-1.22)], or wait time [Stage I 0.45 (-0.61-1.50), Stage II 0.33 (-0.86-1.52), Stage III 3.03 (-0.05-6.12)]. In exploratory analysis, new immigrants did not have surgery more than established immigrants (12.9% vs. 10.1%), and refugee women had longer wait time compared with economic-class immigrants (39.5 vs. 35.3 days).

CONCLUSIONS

We observed differences in measures of socioeconomic disadvantage and disease characteristics between immigrant and Canadian-born women with breast cancer. Upon adjusting for these factors, no differences emerged in rate of surgery, rate of BCS, and time to surgery. The lack of disparity suggests barriers to accessing basic components of breast cancer care may be mitigated by the universal healthcare system in Canada.

Evaluating the Association between the Implementation of the PoET (Prevention of Error-Based Transfers) Southwest Spread Project and Palliative Care Provision: A Quasi-Experimental Matched Cohort Study Using Population-Level Health Administrative Data

OBJECTIVES

The PoET (Prevention of Error-based Transfers) project seeks to align long-term care (LTC) home informed consent practices to existing legislation, thereby reducing consent-related error-based transfers to acute care. We sought to measure changes in resident-level palliative care provision after participating in the PoET Southwest Spread Project (PSSP), and to identify patient and LTC home characteristics associated with palliative care provision.

DESIGN

Quasi-experimental matched (1:1 ratio) cohort study design using linked population-based health administrative data.

SETTING

Sixty LTC homes (PSSP = 30; Control = 30) in Ontario, Canada, from November 2019 to December 2021.

METHODS

We matched 30 PSSP to 30 control homes and described incidence rates for resident-level palliative care provision (ie, physician palliative care encounters and palliative medication prescriptions) during the 7-month postimplementation period. We used generalized linear mixed models to evaluate the association between PSSP implementation and palliative care provision during the postimplementation period. We adjusted for resident-level characteristics (ie, age, sex, comorbidity status) and home-level characteristics (ie, rurality status, profit model, COVID-19 impact). We identified a decedent subcohort to measure palliative care provision patterns during the last 2 months of life.

RESULTS

We captured a matched cohort of 8894 residents (PSSP = 4103; Control = 4791). Incidence rates of palliative care encounters increased during the postimplementation period for PSSP (82.6 to 85.4 per 100 person-months) but not for control residents (68.8 to 65.3 per 100 person-months). After adjusting for key covariates, PSSP exposure was associated increased palliative care provision (incidence rate ratio 2.47, 95% CI 2.31-2.64) and palliative care medication prescription (1.16, 95% CI 1.12-1.20). Larger home size, certain health regions, and higher number of comorbidities were associated with increased physician palliative care encounters.

CONCLUSIONS AND IMPLICATIONS

By promoting correct informed consent practices in LTC, PSSP participation increased palliative care provision for PSSP LTC residents across all settings.

Evaluating the Association between the Implementation of the PoET Southwest Spread Project and Reductions in Acute Care Transfers from Long-Term Care: A Quasi-Experimental Matched Cohort Study Using Population-Level Health Administrative Data

OBJECTIVES

To measure changes in resident-level acute care transfer rates after the PoET Southwest Spread Project (PSSP), and to identify patient and long-term care (LTC) home characteristics associated with acute care transfers after program launch.

DESIGN

Quasi-experimental matched (1:1 ratio) cohort study design using linked population-based health administrative data.

SETTING

Sixty publicly funded LTC homes (PSSP = 30; control = 30) in Ontario, Canada, from November 2019 to December 2021.

METHODS

We matched 30 PSSP homes to 30 control homes with similar characteristics and described incidence rates for resident-level acute care transfers during the 7-month post-implementation period. We used generalized linear mixed models to evaluate the association between PSSP implementation and acute care transfers during the post-implementation period. We adjusted resident-level characteristics (ie, age, sex, comorbidity status) and home-level characteristics (ie, rurality status, profit model, COVID-19 impact). We identified a decedent sub-cohort to measure transfer patterns during the last 2 months of life.

RESULTS

A matched cohort of 8894 residents (PSSP = 4103; control = 4791) was captured. Incidence rates of transfers increased during the post-implementation period for both PSSP (78.8 to 80.9 transfers per 1000 person-months) and control residents (66.9 to 67.9 transfers per 1000 person-months). After adjusting for covariates of interest, PSSP exposure was associated with a reduction in acute care transfers during the post-implementation period after adjusting for covariates (incidence rate ratio, 0.73; 95% CI, 0.62-0.87; P = .0002). Older age and select health regions were associated with reduced transfers, whereas higher comorbidity status and higher COVID-19 outbreak days were associated with increases. Similar patterns persisted for transfers during the last 2 months of life.

CONCLUSIONS AND IMPLICATIONS

This study systematically evaluated the impact of an ethics-based health care intervention in LTC using health care utilization databases. PoET implementation is associated with reduced acute care transfer rates, especially in the last 2 months of life in LTC.

Validation of Parent-reported Gestational Age Categories for Children Less Than 6 Years of Age

BACKGROUND

Preterm birth is an important outcome or exposure in epidemiologic research. When administrative data on measured gestational age is not available, parent-reported gestational age can be obtained from questionnaires, which is subject to potential bias. To our knowledge, few studies have assessed the validity of parent-reported gestational age categories, including commonly defined categories of preterm birth.

METHODS

We used linked data from primarily healthy children <6 years of age in TARGet Kids! in Toronto, Canada, and ICES administrative healthcare data from April 2011 to March 2020. We assessed the criterion validity of questionnaire-based parent-reported gestational age by calculating sensitivity and specificity for term (≥37 weeks), late preterm (34-36 weeks), and moderately preterm (32-33 weeks) gestational age categories, using administrative healthcare records of gestational age as the criterion standard. We conducted subgroup analyses for various parent and socioeconomic factors that may influence recall.

RESULTS

Of the 4684 participants, 97.3% correctly classified the gestational age category according to administrative healthcare data. Parent-reported gestational age sensitivity ranged from 83.7% to 98.5% and specificity ranged from 88.3% to 99.8%, depending on category. For each subgroup characteristic, sensitivity and specificity were all ≥70%. Lower educational attainment, lower family income, father reporting, ≥1 year since birth, ≥2 children, lower parent age, and reported gestational diabetes and/or hypertension were associated with slightly lower sensitivity and/or specificity.

CONCLUSIONS

In this linked cohort, parent-reported gestational age categories had high accuracy. Criterion validity varied minimally among some parent and socioeconomic factors. Our findings can inform future quantitative bias analyses.

Recent functional decline and outpatient follow-up after hospital discharge: a cohort study

BACKGROUND

Functional decline is common following acute hospitalization and is associated with hospital readmission, institutionalization, and mortality. People with functional decline may have difficulty accessing post-discharge medical care, even though early physician follow-up has the potential to prevent poor outcomes and is integral to high-quality transitional care. We sought to determine whether recent functional decline was associated with lower rates of post-discharge physician follow-up, and whether this association changed during the COVID-19 pandemic, given that both functional decline and COVID-19 may affect access to post-discharge care.

METHOD

We conducted a retrospective cohort study using health administrative data from Ontario, Canada. We included patients over 65 who were discharged from an acute care facility during March 1st, 2019 - January 31st, 2020 (pre-COVID-19 period), and March 1st, 2020 - January 31st, 2021 (COVID-19 period), and who were assessed for home care while in hospital. Patients with and without functional decline were compared. Our primary outcome was any physician follow-up visit within 7 days of discharge. We used propensity score weighting to compare outcomes between those with and without functional decline.

RESULTS

Our study included 21,771 (pre-COVID) and 17,248 (COVID) hospitalized patients, of whom 15,637 (71.8%) and 12,965 (75.2%) had recent functional decline. Pre-COVID, there was no difference in physician follow-up within 7 days of discharge (Functional decline 45.0% vs. No functional decline 44.0%; RR = 1.02, 95% CI 0.98-1.06). These results did not change in the COVID-19 period (Functional decline 51.1% vs. No functional decline 49.4%; RR = 1.03, 95% CI 0.99-1.08, Z-test for interaction p = 0.72). In the COVID-19 cohort, functional decline was associated with having a 7-day physician virtual visit (RR 1.15; 95% CI 1.08-1.24) and a 7-day physician home visit (RR 1.64; 95% CI 1.10-2.43).

CONCLUSIONS

Functional decline was not associated with reduced 7-day post-discharge physician follow-up in either the pre-COVID-19 or COVID-19 periods. In the COVID-19 period, functional decline was positively associated with 7-day virtual and home-visit follow-up.

Late preterm birth and growth trajectories during childhood: a linked retrospective cohort study

BACKGROUND

Evidence suggests that accelerated postnatal growth in children is detrimental for adult cardiovascular health. It is unclear whether children born late preterm (34-36 weeks) compared to full term (≥ 39 weeks), have different growth trajectories. Our objective was to evaluate the association between gestational age groups and growth trajectories of children born between 2006-2014 and followed to 2021 in Ontario, Canada.

METHODS

We conducted a retrospective cohort study of children from singleton births in TARGet Kids! primary care network with repeated measures of weight and height/length from birth to 14 years, who were linked to health administrative databases. Piecewise linear mixed models were used to model weight (kg/month) and height (cm/month) trajectories with knots at 3, 12, and 84 months. Analyses were conducted based on chronological age.

RESULTS

There were 4423 children included with a mean of 11 weight and height measures per child. The mean age at the last visit was 5.9 years (Standard Deviation: 3.1). Generally, the more preterm, the lower the mean value of weight and height until early adolescence. Differences in mean weight and height for very/moderate preterm and late preterm compared to full term were evident until 12 months of age. Weight trajectories were similar between children born late preterm and full term with small differences from 84-168 months (mean difference (MD) -0.04 kg/month, 95% CI -0.06, -0.03). Children born late preterm had faster height gain from 0-3 months (MD 0.70 cm/month, 95% CI 0.42, 0.97) and 3-12 months (MD 0.17 cm/month, 95% CI 0.11, 0.22).

CONCLUSIONS

Compared to full term, children born late preterm had lower average weight and height from birth to 14 years, had a slightly slower rate of weight gain after 84 months and a faster rate of height gain from 0-12 months. Follow-up is needed to determine if growth differences are associated with long-term disease risk.

Rates of Hospital-Based Care among Older Adults in the Community and Residential Care Facilities: A Repeated Cross-Sectional Study

OBJECTIVE

We examine annual rates of emergency department (ED) visits, hospital admissions, and alternate levels of care (ALC) days (ie, the number of days that an older adult remained in hospital when they could not be safely discharged to an appropriate setting in their community) among older adults.

DESIGN

Repeated cross-sectional study.

SETTING AND PARTICIPANTS

Linked, individual-level health system administrative data on community-dwelling persons, home care recipients, residents of assisted living facilities, and residents of nursing homes aged 65 years and older in Ontario, Canada, from January 1, 2013, to December 31, 2019.

METHODS

We calculated rates of ED visits, hospital admissions, and ALC days per 1000 individuals per older adult population per year. We used a generalized linear model with a gaussian distribution, log link, and year fixed effects to obtain rate ratios.

RESULTS

There were 1,655,656 older adults in the community, 237,574 home care recipients, 42,600 older adults in assisted living facilities, and 94,055 older adults in nursing homes in 2013; there were 2,129,690 older adults in the community, 281,028 home care recipients, 56,975 older adults in assisted living facilities, and 95,925 older adults in nursing homes in 2019. Residents of assisted living facilities had the highest rates of ED visits (1260.692019 vs 1174.912013), hospital admissions (482.632019 vs 480.192013), and ALC days (1905.572019 vs 1443.032013) per 1000 individuals. Residents of assisted living facilities also had significantly higher rates of ED visits [rate ratio (RR) 3.30, 95% CI 3.20, 3.41), hospital admissions (RR 6.24, 95% CI 6.01, 6.47), and ALC days (RR 25.68, 95% CI 23.27, 28.35) relative to community-dwelling older adults.

CONCLUSIONS AND IMPLICATIONS

The disproportionate use of ED visits, hospital admissions, and ALC days among residents of assisted living facilities may be attributed to the characteristics of the population and fragmented licensing and regulation of the sector, including variable models of care. The implementation of interdisciplinary, after-hours, team-based approaches to home and primary care in assisted living facilities may reduce the potentially avoidable use of ED visits, hospital admissions, and ALC days among this population and optimize resource allocation in health care systems.

Clinical Comorbidities and Transitions Between Care Settings Among Residents of Assisted Living Facilities: A Repeated Cross-Sectional Study

OBJECTIVE

We investigate the changes in the sociodemographic characteristics, clinical comorbidities, and transitions between care settings among residents of assisted living facilities.

DESIGN

Repeated cross-sectional study.

SETTING AND PARTICIPANTS

Linked, individual-level health system administrative data on residents of assisted living facilities in Ontario, Canada, from January 1, 2013, to December 31, 2019.

METHODS

Counts and proportions were calculated to describe the sociodemographic characteristics and clinical comorbidities. Relative changes and trend tests were calculated to quantify the longitudinal changes in the characteristics of residents of assisted living facilities between 2013 and 2019. A Sankey plot was graphed to display transitions between different care settings (ie, hospital admission, nursing home admission, died, or remained in the assisted living facility) each year from 2013 to 2019.

RESULTS

There was a 34% relative increase in the resident population size of assisted living facilities (56,9752019 vs 42,6002013). These older adults had a mean age of 87 years, and women accounted for nearly two-thirds of the population across all years. The 5 clinical comorbidities that had the highest relative increases were renal disease (24.3%), other mental health conditions (16.8%), cardiac arrhythmias (9.6%), diabetes (8.5%), and cancer (6.9%). Nearly 20% of the original cohort from 2013 remained in an assisted living facility at the end of 2019, and approximately 10% of that cohort transitioned to a nursing home in any year from 2013 to 2019.

CONCLUSIONS AND IMPLICATIONS

Residents of assisted living facilities are an important older adult population that has progressively increased in clinical complexity within less than a decade. Clinicians and policy makers should advocate for the implementation of on-site medical care that is aligned with the needs of these older adults.

Did the Long-Term Care Physician Workforce Change During the Pandemic? Describing MRP Trends in Ontario, Canada

OBJECTIVES

To examine the practice patterns and trends of long-term care (LTC) physicians between 2019 and 2021 in Ontario, Canada.

DESIGN

Population-level descriptive time trend study.

SETTING AND PARTICIPANTS

Most responsible physicians (MRPs) of LTC residents of publicly funded LTC homes in Ontario, Canada, from September 2019 to December 2021.

METHODS

We examined the number of MRPs in publicly regulated Ontario LTC homes before and during the COVID-19 pandemic using population-level administrative databases. Characteristics of MRPs and practice patterns were generated at baseline and across distinct time periods of the pandemic in descriptive tables. We created a Sankey diagram to visualize MRP practice changes over time.

RESULTS

More than one-quarter of pre-pandemic MRPs were no longer MRPs by the end of 2021, although most continued to practice in non-LTC settings. There was a decrease from 1444 to 1266 MRPs over time. Other characteristics of MRPs remained stable over the pandemic time periods. At baseline, LTC physicians were MRP for an average of 57.3 residents. By the end of 2021, this caseload decreased to 53.3 residents per MRP. MRPs increasingly billed monthly management compensation fees over the fee-for-service model across the pandemic time periods. The number of MRPs working in an LTC home shifted to fewer MRPs per home.

CONCLUSIONS AND IMPLICATIONS

MRP demographic characteristics did not change over the course of the pandemic. The observed shifts in practice patterns showed a reduction in the overall LTC MRP workforce, who delivered care to fewer residents on average in LTC homes with fewer colleagues to rely on. Future work can study how changes to LTC MRPs' practice patterns impact physician coverage, access and continuity of care, and health services and quality outcomes among residents.

Patient reported symptom burden amongst immigrant and Canadian long-term resident women undergoing breast cancer surgery

PURPOSE

Immigrants are susceptible to marginalization due to social isolation, economic disadvantage and systemic bias. Our goal was to compare symptom burden between immigrant and long-term resident women undergoing breast cancer surgery in Ontario, Canada.

METHODS

A population-level retrospective cohort-study using administrative databases was conducted. Women who underwent surgery for newly diagnosed breast cancer and were treated at regional cancer centers between 2010 and 2016 were included. The primary outcome was a moderate or severe (≥ 4) symptom score on the Edmonton Symptom Assessment System Scale (ESAS).

RESULTS

There were 12,250 (87.2%) long-term Canadian residents and 1,806(12.8%) immigrants. Immigrants were younger (mean age 53 vs. 61 years); had a higher proportion residing in a lowest income quintile neighbourhood (22.2% vs 15.4%); were less often on a primary-care physician roster (83.7% vs. 90.4%); and were less often diagnosed with Stage I/II disease (80.9% vs. 84.6%) (all p < 0.01). The proportion of women with scores ≥ 4 was significantly higher amongst immigrant women for 7/9 symptom categories; with the largest differences for depression (24.9% vs. 20.2%, p < 0.01) and pain (28.0% vs. 22.4%, p < 0.01). On multivariable regression analysis, immigration status was associated with scores ≥ 4 for pain (OR 1.13, 95% CI 1.02-1.23). There was an association between moderate/severe pain and region of origin, but not length of stay in Canada or immigration class.

CONCLUSIONS

This is the first study comparing symptom burden amongst immigrant and non-immigrant women with breast cancer at a population-level. Immigrant women with breast cancer undergoing surgery were found to have a higher burden of pain.

Abstract P4-03-28: Patient Reported Symptom Burden Amongst Immigrant and Canadian Long-Term Resident Women Undergoing Breast Cancer Surgery

Background: Disparities in breast cancer outcomes are well documented, with a burgeoning body of literature shedding light on the influence of multiple factors. Much of the literature comes from the US, with the current situation in Canada less well understood. Canada’s universal health care system may mitigate some, but unlikely all differences. First generation immigrants compromise 21.9% of the Canadian population. Differences in breast cancer screening rates and stage at diagnosis have been demonstrated between immigrant and non-immigrant Canadian women. However, breast cancer outcomes in the Canadian immigrant population have not been well studied. Patient reported outcomes are one such set of outcomes and crucial in understanding the patient experience. The purpose of this study is to compare symptom burden and trajectories between immigrant and Canadian long-term resident women with breast cancer undergoing breast cancer surgery in Ontario. Methods: A population-level retrospective cohort-study using linked Ontario administrative databases was constructed. Women &gt;18 years of age with newly diagnosed breast cancer between 2010-2016 undergoing surgery at a regional cancer center were included. Baseline variables including immigration status, age, stage, comorbidity and income quintile were collected. The proportion of patients reporting moderate/severe Edmonton Symptom Assessment System Scale (ESAS) scores for each of 9 individual symptom categories over time was collected. Multivariable logistic regression models using generalized estimating equations with exchangeable correlation structure to account for repeated measures were constructed to assess the probability of a moderate/severe score for each of the individual ESAS symptom categories. Results: The cohort included 14,056 women, of which 12,250 (87.2%) were categorized as long-term Canadian residents and 1,806 (12.8%) as immigrants. Immigrant women had a younger mean age of diagnosis (53 vs. 61 years), were more likely to reside in a lowest income quintile neighbourhood (22.2% vs 15.4%), were less likely to be on a primary care physician roster within the last 2 years (83.7% vs. 90.4%) and were less often diagnosed with Stage I/II disease (80.9% vs. 84.6%) (all p&lt; 0.0001). The proportion of women reporting moderate/severe scores was significantly higher amongst immigrant women for 7/9 symptom categories (anxiety, depression, drowsiness, nausea, pain, shortness of breath and well-being) with the largest difference observed for depression (13.1% vs 10.8%, p&lt; 0.0001) and pain (14.8% vs. 12.0%, p&lt; 0.0001). Comparing symptom trajectories, differences between groups were most pronounced within the first 12 months, though for depression and pain, statistically significant differences also existed at 36 months. On multivariable regression analysis, immigration status was persistently associated with higher proportion of moderate/severe score for pain only (OR 1.12, 95% CI 1.02-1.23). Immigration status was associated with a protective effect for anxiety (OR 0.86, 95% CI 0.78-0.94), drowsiness (OR 0.81, 95% CI 0.73-0.89) and tiredness (OR 0.86, 95% CI 0.79-0.94). Conclusions: To our knowledge, this is the first study comparing symptom burden amongst immigrant and non-immigrant Canadian women with breast cancer at a population-level. Immigrant women undergoing breast cancer surgery were found to have a higher burden of symptoms across most categories, and for depression and pain this difference was found to persist even at 3-years. However, the higher burden of symptoms in many categories seemed to be explained by factors such as younger age and more advanced disease. Adjusting for other factors, immigrant women with breast cancer reported more pain, indicating a need for better symptom management in this population.

Citation Format: Elena Parvez, Megan M. Chu, David Kirkwood, Aristithes Doumouras, Jessica Bogach. Patient Reported Symptom Burden Amongst Immigrant and Canadian Long-Term Resident Women Undergoing Breast Cancer Surgery. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-03-28.

Examining the immediate and ongoing impact of the COVID-19 pandemic on population-based estimates of dementia: a population-based time series analysis in Ontario, Canada

OBJECTIVES

Population-based chronic disease surveillance systems were likely disrupted by the COVID-19 pandemic. The objective of this study was to examine the immediate and ongoing impact of the COVID-19 pandemic on the claims-based incidence of dementia.

METHODS

We conducted a population-based time series analysis from January 2015 to December 2021 in Ontario, Canada. We calculated the monthly claims-based incidence of dementia using a validated case ascertainment algorithm drawing from routinely collected health administrative data. We used autoregressive linear models to compare the claims-based incidence of dementia during the COVID-19 period (2020-2021) to the expected incidence had the pandemic not occurred, controlling for seasonality and secular trends. We examined incidence by source of ascertainment and across strata of sex, age, community size and number of health conditions.

RESULTS

The monthly claims-based incidence of dementia dropped from a 2019 average of 11.9 per 10 000 to 8.5 per 10 000 in April 2020 (32.6% lower than expected). The incidence returned to expected levels by late 2020. Across the COVID-19 period there were a cumulative 2990 (95% CI 2109 to 3704) fewer cases of dementia observed than expected, equivalent to 1.05 months of new cases. Despite the overall recovery, ascertainment rates continued to be lower than expected among individuals aged 65-74 years and in large urban areas. Ascertainment rates were higher than expected in hospital and among individuals with 11 or more health conditions.

CONCLUSIONS

The claims-based incidence of dementia recovered to expected levels by late 2020, suggesting minimal long-term changes to population-based dementia surveillance. Continued monitoring of claims-based incidence is necessary to determine whether the lower than expected incidence among individuals aged 65-74 and in large urban areas, and higher than expected incidence among individuals with 11 or more health conditions, is transitory.

MIBI-TOF: A multiplexed imaging platform relates cellular phenotypes and tissue structure

Understanding tissue structure and function requires tools that quantify the expression of multiple proteins while preserving spatial information. Here, we describe MIBI-TOF (multiplexed ion beam imaging by time of flight), an instrument that uses bright ion sources and orthogonal time-of-flight mass spectrometry to image metal-tagged antibodies at subcellular resolution in clinical tissue sections. We demonstrate quantitative, full periodic table coverage across a five-log dynamic range, imaging 36 labeled antibodies simultaneously with histochemical stains and endogenous elements. We image fields of view up to 800 μm × 800 μm at resolutions down to 260 nm with sensitivities approaching single-molecule detection. We leverage these properties to interrogate intrapatient heterogeneity in tumor organization in triple-negative breast cancer, revealing regional variability in tumor cell phenotypes in contrast to a structured immune response. Given its versatility and sample back-compatibility, MIBI-TOF is positioned to leverage existing annotated, archival tissue cohorts to explore emerging questions in cancer, immunology, and neurobiology.

Depth profiling of sterically-stabilised polystyrene nanoparticles using laser ablation/ionisation mass spectrometric methods

An aerodynamic lens has been used to introduce polystyrene nanoparticles into an apparatus that combines laser vaporisation with mass spectrometric measurements of ion intensity. The particles have a mean diameter of 129 nm and are sterically-stabilised with poly(ethylene glycol) which coats the surface to a depth of approximately 5 nm. Measurements have been made at wavelengths of 266, 355, and 523 nm, and over a range of laser powers. The results provide clear evidence that depth profiling can be achieved by changing the wavelength of the ablating radiation, but that changes in power at a single wavelength have little influence on the range of ions observed. At 523 nm the mass spectra are predominantly derived from surface-bound material, whilst at 266 nm the dominant contribution is from ions related to the polystyrene core of the particles. It is proposed that these differences in behaviour can be equated with existing models of the laser ablation process.

The effect of stem geometry on stresses within the distal cement mantle in total hip replacement

Cement-stem debonding is one of the most common reasons for failure in Total Hip Replacement (THR). Four similar THR prostheses design configurations were investigated with reference to the influence of mechanical stress occurring in a cement mantle of differing thicknesses and potentially affecting clinical performance. Non-linear finite element analysis was performed on constant cement mantle thicknesses of 1, 2, and 4 millimetres. The results obtained indicate stress levels within the cement mantle decrease with increasing cement mantle thickness. The prosthesis distal tip is shown to have particular significance. Truncation of the distal tip hemisphere to a flat profile for the fixation of a centralizer increases the cement stresses.

The floristics of Sand Forest in northern KwaZulu-Natal, South Africa

We use multivariate analyses (ordination and classification) to assess both the floristic uniqueness of the woody vegeation of Sand Forest in relation to a range of other forest types in the region, and the range of variation within Sand Forest. Two broad Sand Forest subtypes and related Ecotonal Forests are described and grouped under the term Tropical Dry Forest, distinct from all evergreen forests in South Africa. Sand Forest, a dry semi-deciduous type in northeastern KwaZulu-Natals defined by the presence of the canopy dominant Cleistanthus schlechteri as well as Hymenocardia ulmoides, Psydrax fragrantissima, Croton pseudopulchellus and  Drypetes arguta. Sand Forests form a cohesive group in both DCA and TWINSPAN analyses, with similar composition of canopy dominants at sampled sites. This implies that ecological funcioning is similar across the geographical range in northeastern KwaZulu-Natal. However, turnover of subdominant species between recognisable Sand Forest types emphasizes the need to conserve the full range of extant forests.