In vivo effects of cell seeding technique in an ex vivo regional gene therapy model for bone regeneration.

When delivering cells on a scaffold to treat a bone defect, the cell seeding technique determines the number and distribution of cells within a scaffold, however the optimal technique has not been established. This study investigated if human adipose-derived stem cells (ASCs) transduced with a lentiviral vector to overexpress bone morphogenetic protein 2 (BMP-2) and loaded on a scaffold using dynamic orbital shaker could reduce the total cell dose required to heal a critical sized bone defect when compared with static seeding. Human ASCs were loaded onto a collagen/biphasic ceramic scaffold using static loading and dynamic orbital shaker techniques, compared with our labs standard loading technique, and implanted into femoral defects of nude rats. Both a low dose and standard dose of transduced cells were evaluated. Outcomes investigated included BMP-2 production, radiographic healing, micro-computerized tomography, histologic assessment, and biomechanical torsional testing. BMP-2 production was higher in the orbital shaker cohort compared with the static seeding cohort. No statistically significant differences were noted in radiographic, histomorphometric, and biomechanical outcomes between the low-dose static and dynamic seeding groups, however the standard-dose static seeding cohort had superior biomechanical properties. The standard-dose 5 million cell dose standard loading cohort had superior maximum torque and torsional stiffness on biomechanical testing. The use of orbital shaker technique was labor intensive and did not provide equivalent biomechanical results with the use of fewer cells.

Translational and Therapeutic Evaluation of RAS-GTP Inhibition by RMC-6236 in RAS-Driven Cancers.

RAS-driven cancers comprise up to 30% of human cancers. RMC-6236 is a RAS(ON) multi-selective noncovalent inhibitor of the active, GTP-bound state of both mutant and wild-type variants of canonical RAS isoforms with broad therapeutic potential for the aforementioned unmet medical need. RMC-6236 exhibited potent anticancer activity across RAS-addicted cell lines, particularly those harboring mutations at codon 12 of KRAS. Notably, oral administration of RMC-6236 was tolerated in vivo and drove profound tumor regressions across multiple tumor types in a mouse clinical trial with KRASG12X xenograft models. Translational PK/efficacy and PK/PD modeling predicted that daily doses of 100 mg and 300 mg would achieve tumor control and objective responses, respectively, in patients with RAS-driven tumors. Consistent with this, we describe here objective responses in two patients (at 300 mg daily) with advanced KRASG12X lung and pancreatic adenocarcinoma, respectively, demonstrating the initial activity of RMC-6236 in an ongoing phase I/Ib clinical trial (NCT05379985). SIGNIFICANCE: The discovery of RMC-6236 enables the first-ever therapeutic evaluation of targeted and concurrent inhibition of canonical mutant and wild-type RAS-GTP in RAS-driven cancers. We demonstrate that broad-spectrum RAS-GTP inhibition is tolerable at exposures that induce profound tumor regressions in preclinical models of, and in patients with, such tumors.

Tumor-selective activity of RAS-GTP inhibition in pancreatic cancer.

Broad-spectrum RAS inhibition holds the potential to benefit roughly a quarter of human cancer patients whose tumors are driven by RAS mutations1,2. RMC-7977 is a highly selective inhibitor of the active GTP-bound forms of KRAS, HRAS, and NRAS, with affinity for both mutant and wild type (WT) variants (RAS(ON) multi-selective)3. As >90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS4, we assessed the therapeutic potential of the RAS(ON) multi-selective inhibitor RMC-7977 in a comprehensive range of PDAC models. We observed broad and pronounced anti-tumor activity across models following direct RAS inhibition at exposures that were well-tolerated in vivo. Pharmacological analyses revealed divergent responses to RMC-7977 in tumor versus normal tissues. Treated tumors exhibited waves of apoptosis along with sustained proliferative arrest whereas normal tissues underwent only transient decreases in proliferation, with no evidence of apoptosis. In the autochthonous KPC model, RMC-7977 treatment resulted in a profound extension of survival followed by on-treatment relapse. Analysis of relapsed tumors identified Myc copy number gain as a prevalent candidate resistance mechanism, which could be overcome by combinatorial TEAD inhibition in vitro. Together, these data establish a strong preclinical rationale for the use of broad-spectrum RAS-GTP inhibition in the setting of PDAC and identify a promising candidate combination therapeutic regimen to overcome monotherapy resistance.

Concurrent inhibition of oncogenic and wild-type RAS-GTP for cancer therapy.

RAS oncogenes (collectively NRAS, HRAS and especially KRAS) are among the most frequently mutated genes in cancer, with common driver mutations occurring at codons 12, 13 and 611. Small molecule inhibitors of the KRAS(G12C) oncoprotein have demonstrated clinical efficacy in patients with multiple cancer types and have led to regulatory approvals for the treatment of non-small cell lung cancer2,3. Nevertheless, KRASG12C mutations account for only around 15% of KRAS-mutated cancers4,5, and there are no approved KRAS inhibitors for the majority of patients with tumours containing other common KRAS mutations. Here we describe RMC-7977, a reversible, tri-complex RAS inhibitor with broad-spectrum activity for the active state of both mutant and wild-type KRAS, NRAS and HRAS variants (a RAS(ON) multi-selective inhibitor). Preclinically, RMC-7977 demonstrated potent activity against RAS-addicted tumours carrying various RAS genotypes, particularly against cancer models with KRAS codon 12 mutations (KRASG12X). Treatment with RMC-7977 led to tumour regression and was well tolerated in diverse RAS-addicted preclinical cancer models. Additionally, RMC-7977 inhibited the growth of KRASG12C cancer models that are resistant to KRAS(G12C) inhibitors owing to restoration of RAS pathway signalling. Thus, RAS(ON) multi-selective inhibitors can target multiple oncogenic and wild-type RAS isoforms and have the potential to treat a wide range of RAS-addicted cancers with high unmet clinical need. A related RAS(ON) multi-selective inhibitor, RMC-6236, is currently under clinical evaluation in patients with KRAS-mutant solid tumours (ClinicalTrials.gov identifier: NCT05379985).

Single center utilization and post-transplant outcomes of thoracoabdominal normothermic regional perfusion deceased cardiac donor organs.

INTRODUCTION: Thoracoabdominal normothermic regional perfusion (TA-NRP) following cardiac death is an emerging multivisceral organ procurement technique. Recent national studies on outcomes of presumptive TA-NRP-procured organs are limited by potential misclassification since TA-NRP is not differentiated from donation after cardiac death (DCD) in registry data. METHODS: We studied 22 donors whose designees consented to TA-NRP and organ procurement performed at our institution between January 20, 2020 and July 3, 2022. We identified these donors in SRTR to describe organ utilization and recipient outcomes and compared them to recipients of traditional DCD (tDCD) and donation after brain death (DBD) organs during the same timeframe. RESULTS: All 22 donors progressed to cardiac arrest and underwent TA-NRP followed by heart, lung, kidney, and/or liver procurement. Median donor age was 41 years, 55% had anoxic brain injury, 45% were hypertensive, 0% were diabetic, and median kidney donor profile index was 40%. TA-NRP utilization was high across all organ types (88%-100%), with a higher percentage of kidneys procured via TA-NRP compared to tDCD (88% vs. 72%, p = .02). Recipient and graft survival ranged from 89% to 100% and were comparable to tDCD and DBD recipients (p ≥ .2). Delayed graft function was lower for kidneys procured from TA-NRP compared to tDCD donors (27% vs. 44%, p = .045). CONCLUSION: Procurement from TA-NRP donors yielded high organ utilization, with outcomes comparable to tDCD and DBD recipients across organ types. Further large-scale study of TA-NRP donors, facilitated by its capture in the national registry, will be critical to fully understand its impact as an organ procurement technique.

Longitudinal Lower Airway Microbial Signatures of Acute Cellular Rejection in Lung Transplantation.

Rationale: Acute cellular rejection (ACR) after lung transplantation is a leading risk factor for chronic lung allograft dysfunction. Prior studies have demonstrated dynamic microbial changes occurring within the allograft and gut that influence local adaptive and innate immune responses. However, the lung microbiome's overall impact on ACR risk remains poorly understood. Objective: To evaluate whether temporal changes in microbial signatures were associated with the development of ACR. Methods: We performed cross-sectional and longitudinal analyses (joint modeling of longitudinal and time-to-event data and trajectory comparisons) of 16S rRNA gene sequencing results derived from lung transplant recipient lower airway samples collected at multiple timepoints. Measurements and Main Results: Among 103 lung transplant recipients, 25 (24.3%) developed ACR. In comparing samples acquired one month after transplant, subjects who never developed ACR demonstrated lower airway enrichment with several oral commensals (e.g., Prevotella and Veillonella spp.) compared to those with current or future (beyond one month) ACR. However, a subgroup analysis of those who developed ACR beyond one month revealed delayed enrichment with oral commensals occurring at the time of ACR diagnosis compared to baseline, when enrichment with more traditionally pathogenic taxa was present. In longitudinal models, dynamic changes in alpha diversity (characterized by an initial decrease and a subsequent increase) and in the taxonomic trajectories of numerous oral commensals were more commonly observed in subjects with ACR. Conclusion: Dynamic changes in the lower airway microbiota are associated with the development of ACR, supporting its potential role as a useful biomarker or in ACR pathogenesis.

Wilms' tumor 1 (WT1) antigen is overexpressed in Kaposi Sarcoma and is regulated by KSHV vFLIP.

In people living with HIV, Kaposi Sarcoma (KS), a vascular neoplasm caused by KS herpesvirus (KSHV/HHV-8), remains one of the most common malignancies worldwide. Individuals living with HIV, receiving otherwise effective antiretroviral therapy, may present with extensive disease requiring chemotherapy. Hence, new therapeutic approaches are needed. The Wilms' tumor 1 (WT1) protein is overexpressed and associated with poor prognosis in several hematologic and solid malignancies and has shown promise as an immunotherapeutic target. We found that WT1 was overexpressed in >90% of a total 333 KS biopsies, as determined by immunohistochemistry and image analysis. Our largest cohort from ACTG, consisting of 294 cases was further analyzed demonstrating higher WT1 expression was associated with more advanced histopathologic subtypes. There was a positive correlation between the proportion of infected cells within KS tissues, assessed by expression of the KSHV-encoded latency-associated nuclear antigen (LANA), and WT1 positivity. Areas with high WT1 expression showed sparse T-cell infiltrates, consistent with an immune evasive tumor microenvironment. We show that major oncogenic isoforms of WT1 are overexpressed in primary KS tissue and observed WT1 upregulation upon de novo infection of endothelial cells with KSHV. KSHV latent viral FLICE-inhibitory protein (vFLIP) upregulated total and major isoforms of WT1, but upregulation was not seen after expression of mutant vFLIP that is unable to bind IKKÆ´ and induce NFκB. siRNA targeting of WT1 in latent KSHV infection resulted in decreased total cell number and pAKT, BCL2 and LANA protein expression. Finally, we show that ESK-1, a T cell receptor-like monoclonal antibody that recognizes WT1 peptides presented on MHC HLA-A0201, demonstrates increased binding to endothelial cells after KSHV infection or induction of vFLIP expression. We propose that oncogenic isoforms of WT1 are upregulated by KSHV to promote tumorigenesis and immunotherapy directed against WT1 may be an approach for KS treatment.

Applying deep learning to segmentation of murine lung tumors in pre-clinical micro-computed tomography.

Lung cancer remains a leading cause of cancer-related death, but scientists have made great strides in developing new treatments recently, partly owing to the use of genetically engineered mouse models (GEMMs). GEMM tumors represent a translational model that recapitulates human disease better than implanted models because tumors develop spontaneously in the lungs. However, detection of these tumors relies on in vivo imaging tools, specifically micro-Computed Tomography (micro-CT or µCT), and image analysis can be laborious with high inter-user variability. Here we present a deep learning model trained to perform fully automated segmentation of lung tumors without the interference of other soft tissues. Trained and tested on 100 3D µCT images (18,662 slices) that were manually segmented, the model demonstrated a high correlation to manual segmentations on the testing data (r2=0.99, DSC=0.78) and on an independent dataset (n = 12 3D scans or 2328 2D slices, r2=0.97, DSC=0.73). In a comparison against manual segmentation performed by multiple analysts, the model (r2=0.98, DSC=0.78) performed within inter-reader variability (r2=0.79, DSC=0.69) and close to intra-reader variability (r2=0.99, DSC=0.82), all while completing 5+ hours of manual segmentations in 1 minute. Finally, when applied to a real-world longitudinal study (n = 55 mice), the model successfully detected tumor progression over time and the differences in tumor burden between groups induced with different virus titers, aligning well with more traditional analysis methods. In conclusion, we have developed a deep learning model which can perform fast, accurate, and fully automated segmentation of µCT scans of murine lung tumors.

Double-Barrel Vascularized Free Fibula Flap for Reconstruction of Sternal Nonunion with Bone Defect: A Case Report.

CASE: Given the rare incidence of sternal nonunion after traumatic injury, literature describing the management of posttraumatic sternal reconstruction is limited. We present a case of a 54-year-old man with a history of traumatic chest wall injury with multiple unsuccessful attempts at sternal repair who presented with chronic sternal nonunion and persistent bone defect. Sternal reconstruction using a vascularized double-barrel free fibula flap with rigid fixation in multiple planes was performed, with confirmed bony union at 6 months. CONCLUSION: This novel approach to sternal nonunion management allowed effective bridging of posttraumatic sternal bone defects while facilitating osseous integration and long-term stabilization.

Tumor-selective effects of active RAS inhibition in pancreatic ductal adenocarcinoma.

Broad-spectrum RAS inhibition holds the potential to benefit roughly a quarter of human cancer patients whose tumors are driven by RAS mutations. However, the impact of inhibiting RAS functions in normal tissues is not known. RMC-7977 is a highly selective inhibitor of the active (GTP-bound) forms of KRAS, HRAS, and NRAS, with affinity for both mutant and wild type (WT) variants. As >90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS, we assessed the therapeutic potential of RMC-7977 in a comprehensive range of PDAC models, including human and murine cell lines, human patient-derived organoids, human PDAC explants, subcutaneous and orthotopic cell-line or patient derived xenografts, syngeneic allografts, and genetically engineered mouse models. We observed broad and pronounced anti-tumor activity across these models following direct RAS inhibition at doses and concentrations that were well-tolerated in vivo. Pharmacological analyses revealed divergent responses to RMC-7977 in tumor versus normal tissues. Treated tumors exhibited waves of apoptosis along with sustained proliferative arrest whereas normal tissues underwent only transient decreases in proliferation, with no evidence of apoptosis. Together, these data establish a strong preclinical rationale for the use of broad-spectrum RAS inhibition in the setting of PDAC.

Digital spatial profiling to predict recurrence in grade 3 stage I lung adenocarcinoma.

OBJECTIVE: Early-stage lung adenocarcinoma is treated with local therapy alone, although patients with grade 3 stage I lung adenocarcinoma have a 50% 5-year recurrence rate. Our objective is to determine if analysis of the tumor microenvironment can create a predictive model for recurrence. METHODS: Thirty-four patients with grade 3 stage I lung adenocarcinoma underwent surgical resection. Digital spatial profiling was used to perform genomic (n = 31) and proteomic (n = 34) analyses of pancytokeratin positive and negative tumor cells. K-means clustering was performed on the top 50 differential genes and top 20 differential proteins, with Kaplan-Meier recurrence curves based on patient clustering. External validation of high-expression genes was performed with Kaplan-Meier plotter. RESULTS: There were no significant clinicopathologic differences between patients who did (n = 14) and did not (n = 20) have recurrence. Median time to recurrence was 806 days; median follow-up with no recurrence was 2897 days. K-means clustering of pancytokeratin positive genes resulted in a model with a Kaplan-Meier curve with concordance index of 0.75. K-means clustering for pancytokeratin negative genes was less successful at differentiating recurrence (concordance index 0.6). Genes upregulated or downregulated for recurrence were externally validated using available public databases. Proteomic data did not reach statistical significance but did internally validate the genomic data described. CONCLUSIONS: Genomic difference in lung adenocarcinoma may be able to predict risk of recurrence. After further validation, stratifying patients by this risk may help guide who will benefit from adjuvant therapy.

Breastfeeding and Antepartum Breast Milk Expression (BABE): A Randomized Control Trial Utilizing an Electric Breast Pump and its Effect on Postpartum Breastfeeding.

Objective: To evaluate the effect of antenatal breast milk expression (ABE) on exclusive breastfeeding. Materials and Methods: A randomized control study was performed with the primary outcome being formula use during the postpartum hospital stay. Secondary outcomes were the exclusive breastfeeding rate at 6 months postpartum and peripartum safety outcomes. Participants included multiparous and nulliparous patients who planned to breastfeed. Exclusion criteria included exclusively breastfeeding in prior pregnancies for greater than 6 months, medical contraindications for breastfeeding, multiple gestation, history of preterm delivery, or any contraindication to vaginal delivery. ABE group participants were instructed to pump for 20 minutes, three times daily, starting at 37 weeks of gestation. Results: Three-hundred four participants from two clinics were enrolled. There was no significant difference in formula use during hospital admission (odds ratio [OR] 0.64, 95% confidence interval [CI] 0.34-1.22) or in exclusive breastfeeding at 6 months postpartum (OR 0.66, 95% CI 0.34-1.29). Colostrum use was more prevalent in the ABE group (OR 5.31, 95% CI 2.63-10.76). ABE participants were more likely to present in spontaneous labor (OR 2.09, 95% CI 1.05-4.14). Conclusion: ABE did not significantly improve exclusive breastfeeding rates, but safely provides women opportunities to become familiar with breastfeeding before delivery and can provide readily available colostrum. There was no negative secondary safety outcome related to ABE identified. Prenatal care providers can consider recommending ABE to patients with minimal to no experience with breastfeeding.

The Intersection of Race and Sex: A New Perspective Into Diversity Trends in Orthopaedic Surgery.

INTRODUCTION: Studies on diversity in orthopaedic surgery have exclusively examined challenges from a race or sex perspective. This study examines trends in the diversity of entering orthopaedic surgery residents from the intersection of race and sex. METHODS: The American Association of Medical Colleges was queried for individuals entering orthopaedic surgery residencies in the United States from 2001 to 2020. Deidentified data on self-reported sex and race were collected. Proportions by the intersection of sex and race were calculated for 5-year intervals. RESULTS: From 2001 to 2020, most of the new female residents identified as White (mean, 71.0%). The average proportion of White female residents was lower in 2016 to 2020 than in 2001 to 2005 (71.0% vs. 73.2%) but higher than that in 2011 to 2015 (66.8%). The 2016 to 2020 average was lower than that of 2001 to 2005 for those who identified as Asian (11.7% vs. 14.9%), Black (4.1% vs. 4.8%), Hispanic (3.0% vs. 4.4%), and American Indian/Alaska Native (0.0% vs. 1.5%). Most of the new male orthopaedic surgery residents from 2001 to 2020 identified as White (mean, 74.1%), but the average decreased across every 5-year interval from 2001 to 2005 (76.1%) to 2016 to 2020 (71.1%). The 2016 to 2020 average was lower than that of 2001 to 2005 for those who identified as Asian (12.2% vs. 13.6%), Black (3.5% vs. 4.2%), Hispanic (3.0% vs. 3.4%), American Indian/Alaska Native (0.0% vs. 0.6%), and Native Hawaiian/Other Pacific Islander (0.1% vs. 0.3%). In 2020, White male residents made up to 54.2% of new residents. White female residents were the second highest group represented (12.1%). CONCLUSION: Increases in representation were observed for some subgroups of new orthopaedic surgery residents from 2001 to 2020. Although the proportion of both White female and male residents decreased by 11.5% during the 20-year study period, these individuals still made up most of the trainees in 2020. These results underscore the need for conversations and recruitment practices to take into consideration the intersectionality of identities.

Association between Endometriosis and Surgical Complications among Benign Hysterectomies.

STUDY OBJECTIVE: To investigate the effect of endometriosis on perioperative outcomes in patients undergoing hysterectomy for benign disease. DESIGN: A retrospective cohort study. SETTING: The American College of Surgeons National Surgical Quality Improvement Program database. PATIENTS: A total of 127 556 hysterectomies performed for benign gynecologic indications INTERVENTIONS: Differences in the primary outcomes were compared between patients with and without endometriosis after adjustment for group differences in covariates using inverse probability of treatment weighting approach. MEASURES AND MAIN RESULTS: Of the 127 556 hysterectomies identified, 19 618 (15.4%) had a diagnosis of endometriosis. Patients with endometriosis were younger with a lower prevalence of chronic comorbidities but had higher rates of concurrent pelvic inflammatory disease and previous abdominal operations. The incidence of postoperative complications was higher in patients with endometriosis (9.9% vs 8.1%; odds ratio [OR], 1.25; 95% confidence interval [CI], 1.17-1.34). The incidence of 30-day mortality (0.1% vs 0.03%; OR, 1.98; 95% CI, 0.69-5.65) and reoperations (1.50% vs 1.36%; OR, 1.18; 95% CI, 0.98-1.42) were not different in patients with and without endometriosis. CONCLUSION: Postoperative complications are more likely in hysterectomies involving endometriosis than those without endometriosis, likely owing to anatomic distortion incurring increased surgical complexity. Patients and surgeons should be aware of the increased risk of complications and plan for mitigating these increased risks before and during surgery for suspected endometriosis.

Protocol for the development of guidance for collaborator and partner engagement in health care evidence syntheses.

BACKGROUND: Involving collaborators and partners in research may increase relevance and uptake, while reducing health and social inequities. Collaborators and partners include people and groups interested in health research: health care providers, patients and caregivers, payers of health research, payers of health services, publishers, policymakers, researchers, product makers, program managers, and the public. Evidence syntheses inform decisions about health care services, treatments, and practice, which ultimately affect health outcomes. Our objectives are to: A. Identify, map, and synthesize qualitative and quantitative findings related to engagement in evidence syntheses B. Explore how engagement in evidence synthesis promotes health equity C. Develop equity-oriented guidance on methods for conducting, evaluating, and reporting engagement in evidence syntheses METHODS: Our diverse, international team will develop guidance for engagement with collaborators and partners throughout multiple sequential steps using an integrated knowledge translation approach: 1. Reviews. We will co-produce 1 scoping review, 3 systematic reviews and 1 evidence map focusing on (a) methods, (b) barriers and facilitators, (c) conflict of interest considerations, (d) impacts, and (e) equity considerations of engagement in evidence synthesis. 2. Methods study, interviews, and survey. We will contextualise the findings of step 1 by assessing a sample of evidence syntheses reporting on engagement with collaborators and partners and through conducting interviews with collaborators and partners who have been involved in producing evidence syntheses. We will use these findings to develop draft guidance checklists and will assess agreement with each item through an international survey. 3. CONSENSUS: The guidance checklists will be co-produced and finalised at a consensus meeting with collaborators and partners. 4. DISSEMINATION: We will develop a dissemination plan with our collaborators and partners and work collaboratively to improve adoption of our guidance by key organizations. CONCLUSION: Our international team will develop guidance for collaborator and partner engagement in health care evidence syntheses. Incorporating partnership values and expectations may result in better uptake, potentially reducing health inequities.

Biodistribution of lentiviral transduced adipose-derived stem cells for "ex-vivo" regional gene therapy for bone repair.

Ex-vivo gene therapy has been shown to be an effective method for treating bone defects in pre-clinical models. As gene therapy is explored as a potential treatment option in humans, an assessment of the safety profile becomes an important next step. The purpose of this study was to evaluate the biodistribution of viral particles at the defect site and various internal organs in a rat femoral defect model after implantation of human ASCs transduced with lentivirus (LV) with two-step transcriptional activation (TSTA) of bone morphogenetic protein-2 (LV-TSTA-BMP-2). Animals were sacrificed at 4-, 14-, 56-, and 84-days post implantation. The defects were treated with either a standard dose (SD) of 5 million cells or a high dose (HD) of 15 million cells to simulate a supratherapeutic dose. Treatment groups included (1) SD LV-TSTA-BMP-2 (2) HD LV-TSTA-BMP-2, (3) SD LV-TSTA-GFP (4) HD LV-TSTA-GFP and (5) SD nontransduced cells. The viral load at the defect site and ten organs was assessed at each timepoint. Histology of all organs, ipsilateral tibia, and femur were evaluated at each timepoint. There were nearly undetectable levels of LV-TSTA-BMP-2 transduced cells at the defect site at 84-days and no pathologic changes in any organ at all timepoints. In conclusion, human ASCs transduced with a lentiviral vector were both safe and effective in treating critical size bone defects in a pre-clinical model. These results suggest that regional gene therapy using lentiviral vector to treat bone defects has the potential to be a safe and effective treatment in humans.

Prolonged Ischemia Increases Complications Among High- and Low-Volume Centers in Lung Transplantation.

BACKGROUND: The effect of prolonged allograft ischemic time on lung transplant outcomes remains controversial, with most studies associating it with increased mortality, but this effect is partly mitigated by center volume. This study sought to evaluate the mechanism of these findings and clarify the impact of ischemic time on short-term outcomes in a national sample. METHODS: Data on lung transplants (January 2010-Janary 2017) were extracted from the Scientific Registry of Transplant Recipients database. Ischemic time was dichotomized as prolonged ischemic time (PIT) or no PIT (N-PIT) at 6 hours. High-volume centers were defined as the top quintile. The primary outcome was 30-day, 1-year, and 3-year mortality; secondary outcomes included in-hospital complications and 72-hour oxygenation. RESULTS: Among 11,809 records, there were significant differences between PIT and N-PIT recipients by demographics, lung allocation score, and donor organ metrics. In a 1:1 propensity score-matched cohort (n = 6422), PIT recipients had reduced survival compared with N-PIT at 3 years (66.5% vs 68.8%, P = .031). On multivariable analysis, this effect persisted among low-volume but not high-volume centers. PIT recipients were more likely to require reintubation, prolonged (>5 days) mechanical ventilation, hemodialysis, longer stay, and acute rejection (all P < .01). Except for reintubation, these disparities were present at both high- and low-volume centers independently. Ischemic time had no effect on 72-hour oxygenation. CONCLUSIONS: PIT remains associated with higher rates of postoperative complications and reduced short-term survival. While center volume ameliorated the survival impact, this was not achieved by reducing postoperative complications. Further research is warranted before broadening ischemic time thresholds among low-volume centers.