MALTS: Matching After Learning to Stretch

We introduce a flexible framework that produces high-quality almost-exact matches for causal inference. Most prior work in matching uses ad-hoc distance metrics, often leading to poor quality matches, particularly when there are irrelevant covariates. In this work, we learn an interpretable distance metric for matching, which leads to substantially higher quality matches. The learned distance metric stretches the covariate space according to each covariate's contribution to outcome prediction: this stretching means that mismatches on important covariates carry a larger penalty than mismatches on irrelevant covariates. Our ability to learn flexible distance metrics leads to matches that are interpretable and useful for the estimation of conditional average treatment effects.Comment: 40 pages, 5 Tables, 12 Figure

Stratifying Intraductal Papillary Mucinous Neoplasms by Cyst Fluid Analysis: Present and Future

A significant proportion of patients with intraductal papillary mucinous neoplasms (IPMNs) undergo surgical resection in order to prevent or treat pancreatic cancer at the risk of significant perioperative morbidity. Efforts have been made to stratify the potential risk of malignancy based on the clinical and radiographic features of IPMN to delineate which cysts warrant resection versus observation. An analysis of the cyst fluid obtained by preoperative endoscopic examination appears to be correlative of cyst type and risk, whereas serum markers and radiographic findings have not yet reached a level of sensitivity or specificity that proves they are clinically meaningful. In this review, we investigate the current cyst fluid analysis studies and present those that have shown promise in effectively stratifying high-risk versus low-risk lesions. While new cyst fluid markers continue to be identified, additional efforts in testing panels and marker composites in conjunction with clinical algorithms have also shown promise in distinguishing dysplasia and the risk of malignancy. These should be tested prospectively in order to determine their role in guiding the surveillance of low-risk lesions and to evaluate the new markers detected by proteomics and genetic sequencing

Association of race and health insurance in treatment disparities of colon cancer: A retrospective analysis utilizing a national population database in the United States

Background Both health insurance status and race independently impact colon cancer (CC) care delivery and outcomes. The relative importance of these factors in explaining racial and insurance disparities is less clear, however. This study aimed to determine the association and interaction of race and insurance with CC treatment disparities. Study setting Retrospective cohort review of a prospective hospital-based database. Methods and findings In this cross-sectional study, patients diagnosed with stage I to III CC in the United States were identified from the National Cancer Database (NCDB; 2006 to 2016). Multivariable regression with generalized estimating equations (GEEs) were performed to evaluate the association of insurance and race/ethnicity with odds of receipt of surgery (stage I to III) and adjuvant chemotherapy (stage III), with an additional 2-way interaction term to evaluate for effect modification. Confounders included sex, age, median income, rurality, comorbidity, and nodes and margin status for the model for chemotherapy. Of 353,998 patients included, 73.8% (n = 261,349) were non-Hispanic White (NHW) and 11.7% (n = 41,511) were non-Hispanic Black (NHB). NHB patients were less likely to undergo resection [odds ratio (OR) 0.66, 95% confidence interval [CI] 0.61 to 0.72, p < 0.001] or to receive adjuvant chemotherapy [OR 0.83, 95% CI 0.78 to 0.87, p < 0.001] compared to NHW patients. NHB patients with private or Medicare insurance were less likely to undergo resection [OR 0.76, 95% CI 0.63 to 0.91, p = 0.004 (private insurance); OR 0.59, 95% CI 0.53 to 0.66, p < 0.001 (Medicare)] and to receive adjuvant chemotherapy [0.77, 95% CI 0.68 to 0.87, p < 0.001 (private insurance); OR 0.86, 95% CI 0.80 to 0.91, p < 0.001 (Medicare)] compared to similarly insured NHW patients. Although Hispanic patients with private and Medicare insurance were also less likely to undergo surgical resection, this was not the case with adjuvant chemotherapy. This study is mainly limited by the retrospective nature and by the variables provided in the dataset; granular details such as continuity or disruption of insurance coverage or specific chemotherapy agents or dosing cannot be assessed within NCDB. Conclusions This study suggests that racial disparities in receipt of treatment for CC persist even among patients with similar health insurance coverage and that different disparities exist for different racial/ethnic groups. Changes in health policy must therefore recognize that provision of insurance alone may not eliminate cancer treatment racial disparities.ECU ALS PLOS Institutional Account Progra

A Double Machine Learning Approach to Combining Experimental and Observational Data

Experimental and observational studies often lack validity due to untestable assumptions. We propose a double machine learning approach to combine experimental and observational studies, allowing practitioners to test for assumption violations and estimate treatment effects consistently. Our framework tests for violations of external validity and ignorability under milder assumptions. When only one assumption is violated, we provide semi-parametrically efficient treatment effect estimators. However, our no-free-lunch theorem highlights the necessity of accurately identifying the violated assumption for consistent treatment effect estimation. We demonstrate the applicability of our approach in three real-world case studies, highlighting its relevance for practical settings

Towards a quantum theory of de Sitter space

We describe progress towards constructing a quantum theory of de Sitter space in four dimensions. In particular we indicate how both particle states and Schwarzschild de Sitter black holes can arise as excitations in a theory of a finite number of fermionic oscillators. The results about particle states depend on a conjecture about algebras of Grassmann variables, which we state, but do not prove.Comment: JHEP3 LaTex - 19 page

Estimating Trustworthy and Safe Optimal Treatment Regimes

Recent statistical and reinforcement learning methods have significantly advanced patient care strategies. However, these approaches face substantial challenges in high-stakes contexts, including missing data, inherent stochasticity, and the critical requirements for interpretability and patient safety. Our work operationalizes a safe and interpretable framework to identify optimal treatment regimes. This approach involves matching patients with similar medical and pharmacological characteristics, allowing us to construct an optimal policy via interpolation. We perform a comprehensive simulation study to demonstrate the framework's ability to identify optimal policies even in complex settings. Ultimately, we operationalize our approach to study regimes for treating seizures in critically ill patients. Our findings strongly support personalized treatment strategies based on a patient's medical history and pharmacological features. Notably, we identify that reducing medication doses for patients with mild and brief seizure episodes while adopting aggressive treatment for patients in intensive care unit experiencing intense seizures leads to more favorable outcomes

Noniatrogenic Medial Patellar Dislocations: Case Series and International Patellofemoral Study Group Experience

Background: Most patellar dislocations occur in a lateral direction because of a summed lateral force vector and predisposing anatomic risk factors. Medial patellar instability is rare and is a well-recognized iatrogenic complication of an overly aggressive lateral retinacular release. Noniatrogenic medial patellar dislocations are rare. The management of these injuries is not well described. Purpose: To describe the experience of the International Patellofemoral Study Group with patients with noniatrogenic medial patellar dislocation. Study design: Case series; Level of evidence, 4. Methods: Members of the International Patellofemoral Study Group (N = 64) were surveyed between October 2018 and April 2019. This group was chosen because of its wide referral base and interest in patellar instability. Specialists who had encountered a patient with medial patellar instability were sent a questionnaire inquiring about details of the case, including patient demographics, medical history, level of athletic competition, injury characteristics, and treatment. Cases were confirmed by physical examination records and, in some cases, with findings on advanced radiographic imaging. Results: The survey response rate was 73% (47/64). Three of the 47 specialists (6.4%) reported they had seen a case of noniatrogenic medial patellar dislocation, for a total of 6 cases. Four cases were described as recurrent medial dislocations in the setting of hypermobile Ehlers-Danlos syndrome; 2 were treated nonoperatively, 1 underwent lateral patellofemoral ligament reconstruction, and 1 underwent derotational osteotomies. Two medial-sided patellar dislocations in collegiate athletes were sports-related injuries that required surgical debridement but no ligamentous reconstruction. None of the patients had persistent or recurrent instability at the time of their most recent follow-up. Conclusion: Noniatrogenic medial patellar dislocations are extremely rare. This case review suggests that the treatment of first-time medial patellar instability in patients without known risk factors should follow the same principles as the treatment of lateral instability with no known risk factors, which is nonoperative management. For patients with documented risk factors and recurrence, surgery to address the risk factors may be appropriate

Differences in receipt of multimodality therapy by race,insurance status, and socioeconomic disadvantage in patientswith resected pancreatic cancer

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Background and Methods:Racial and socioeconomic disparities in receipt ofadjuvant chemotherapy affect patients with pancreatic cancer. However, differencesin receipt of neoadjuvant chemotherapy among patients undergoing resection arenot well�understood. A retrospective cross�sectional cohort of patients withresected AJCC Stage I/II pancreatic ductal adenocarcinoma was identified fromthe National Cancer Database (2014–2017). Outcomes included receipt ofneoadjuvant versus adjuvant chemotherapy, or receipt of either, defined asmultimodality therapy and were assessed by univariate and multivariate analysis.Results:Of 19 588 patients, 5098 (26%) received neoadjuvant chemotherapy, 9624(49.1%) received adjuvant chemotherapy only, and 4757 (24.3%) received nochemotherapy. On multivariable analysis, Black patients had lower odds ofneoadjuvant chemotherapy compared to White patients (OR: 0.80, 95% CI:0.67–0.97) but no differences in receipt of multimodality therapy (OR: 0.89, 95%CI: 0.77–1.03). Patients with Medicaid or no insurance, low educational attainment,or low median income had significantly lower odds of receiving neoadjuvantchemotherapy or multimodality therapy.Conclusions:Racial and socioeconomic disparities persist in receipt of neoadjuvantand multimodality therapy in patients with resected pancreatic adenocarcinoma.Discussion:Policy and interventional implementations are needed to bridge thecontinued socioeconomic and racial disparity gap in pancreatic cancer care.ECU/Wiley Open Access Publishing Agreemen