Single-center Outcomes After Liver Transplantation With SARS-CoV-2-Positive Donors: An Argument for Increased Utilization

Background

The COVID-19 pandemic has led to an increase in SARS-CoV-2-test positive potential organ donors. The benefits of life-saving liver transplantation (LT) must be balanced against the potential risk of donor-derived viral transmission. Although emerging evidence suggests that the use of COVID-19-positive donor organs may be safe, granular series thoroughly evaluating safety are still needed. Results of 29 consecutive LTs from COVID-19-positive donors at a single center are presented here.

Methods

A retrospective cohort study of LT recipients between April 2020 and December 2022 was conducted. Differences between recipients of COVID-19-positive (n = 29 total; 25 index, 4 redo) and COVID-19-negative (n = 472 total; 454 index, 18 redo) deceased donor liver grafts were compared.

Results

COVID-19-positive donors were significantly younger (P = 0.04) and had lower kidney donor profile indices (P = 0.04) than COVID-19-negative donors. Recipients of COVID-19-positive donor grafts were older (P = 0.04) but otherwise similar to recipients of negative donors. Donor SARS-CoV-2 infection status was not associated with a overall survival of recipients (hazard ratio, 1.11; 95% confidence interval, 0.24-5.04; P = 0.89). There were 3 deaths among recipients of liver grafts from COVID-19-positive donors. No death seemed virally mediated because there was no qualitative association with peri-LT antispike antibody titers, post-LT prophylaxis, or SARS-CoV-2 variants.

Conclusions

The utilization of liver grafts from COVID-19-positive donors was not associated with a decreased overall survival of recipients. There was no suggestion of viral transmission from donor to recipient. The results from this large single-center study suggest that COVID-19-positive donors may be used safely to expand the deceased donor pool.

Liver transplantation as an alternative for the treatment of intrahepatic cholangiocarcinoma: Past, present, and future directions

Intrahepatic cholangiocarcinoma (iCCA) is a rare biliary tract cancer with high mortality rate. Complete resection of the iCCA lesion is the first choice of treatment, with good prognosis after margin-negative resection. Unfortunately, only 12%-40% of patients are eligible for resection at presentation due to cirrhosis, portal hypertension, or large tumor size. Liver transplantation (LT) offers margin-negative iCCA extirpation for patients with unresectable tumors. Initially, iCCA was a contraindication for LT until size-based selection criteria were introduced to identify patients with satisfied post-LT outcomes. Recent studies have shown that tumor biology-based selection can yield high post-LT survival in patients with locally advanced iCCA. Another selection criterion is the tumor response to neoadjuvant therapy. Patients with response to neoadjuvant therapy have better outcomes after LT compared with those without tumor response to neoadjuvant therapy. Another index that helps predict the treatment outcome is the biomarker. Improved survival outcomes have also opened the door for living donor LT for iCCA. Patients undergoing LT for iCCA now have statistically similar survival rates as patients undergoing resection. The combination of surgery and locoregional and systemic therapies improves the prognosis of iCCA patients.

Update on the Screening, Diagnosis, and Management of Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a neoplasm of the biliary tract that has become increasingly prevalent throughout the world. Common risk factors for developing CCA include cirrhosis, primary sclerosing cholangitis, and trematode fluke infestation, although there are no set screening guidelines in high-risk groups. Lesions are typically identified via cross-sectional imaging and/or elevated serum carbohydrate antigen 19-9 levels, often followed by cytology or brushings with fluorescence in situ hybridization for confirmation. Treatments can vary among CCA subtypes but frequently involve systemic therapies such as gemcitabine and cisplatin with durvalumab or pembrolizumab. Targeted therapies may also be effective (eg, ivosidenib, pemigatinib, infigratinib, futibatinib) depending on the molecular alterations present. Resection is the most common surgical treatment for CCA, although liver transplantation is also an option in highly selected patients with liver-limited unresectable disease. Radiotherapy may also be a treatment option, as well as transarterial radioembolization (eg, yttrium-90), which is often utilized in combination with systemic therapy. Although patients with CCA have traditionally had a poor prognosis, recent advances in treatment, including new systemic therapies and increased utilization of liver transplantation, have improved expected survival. This article reviews screening modalities, pros and cons of diagnostic techniques, and therapies that are currently available to treat patients with CCA.

Bloodstream infections after solid organ transplantation: clinical epidemiology and antimicrobial resistance (2016-21)

Background

Solid organ transplant (SOT) recipients are at risk of bloodstream infections (BSIs) with MDR organisms (MDROs).

Objectives

To describe the epidemiology of BSI in the year after several types of SOT, as well as the prevalence of MDRO infections in this population.

Methods

We conducted a single-centre, retrospective study of kidney, liver, heart, and multi-organ transplantation patients. We examined BSIs ≤1 year from SOT and classified MDRO phenotypes for Staphylococcus aureus, enterococci, Enterobacterales, Pseudomonas aeruginosa and Candida spp. We compared BSI characteristics between SOT types and determined risk factors for 90 day mortality.

Results

We included 2293 patients [1251 (54.6%) kidney, 663 (28.9%) liver, 219 (9.6%) heart and 160 (7.0%) multi-organ transplant]. Overall, 8.5% of patients developed a BSI. BSIs were most common after multi-organ (23.1%) and liver (11.3%) transplantation (P < 0.001). Among 196 patients with BSI, 323 unique isolates were recovered, 147 (45.5%) of which were MDROs. MDROs were most common after liver transplant (53.4%). The most frequent MDROs were VRE (69.8% of enterococci) and ESBL-producing and carbapenem-resistant Enterobacterales (29.2% and 27.2% of Enterobacterales, respectively). Mortality after BSI was 9.7%; VRE was independently associated with mortality (adjusted OR 6.0, 95% CI 1.7-21.3).

Conclusions

BSI incidence after SOT was 8.5%, with a high proportion of MDROs (45.5%), especially after liver transplantation. These data, in conjunction with local antimicrobial resistance patterns and prescribing practices, may help guide empirical antimicrobial selection and stewardship practices after SOT.

Molecular profiling in the management of hepatocellular carcinoma

PURPOSE OF REVIEW

The purpose of this review is to both summarize the current knowledge of hepatocellular carcinoma molecular biology and to suggest a framework in which to prospectively translate this knowledge into patient care. This is timely as recent guidelines recommend increased use of these technologies to advance personalized liver cancer care.

RECENT FINDINGS

The main themes covered here address germline and somatic genetic alterations recently discovered in hepatocellular carcinoma, largely owing to next generation sequencing technologies, and nascent efforts to translate these into contemporary practice.

SUMMARY

Early efforts of translating molecular profiling to hepatocellular carcinoma care demonstrate a growing number of potentially actionable alterations. Still lacking are a consensus on what biomarkers and technologies to adopt, at what scale and cost, and how to integrate them most effectively into care.

Modern Outcomes After Liver Retransplantation: A Single-center Experience

BACKGROUND

The need for liver retransplantation (reLT) has increased proportionally with greater numbers of liver transplants (LTs) performed, use of marginal donors, degree of recipient preoperative liver dysfunction, and longer survival after LT. However, outcomes following reLT have been historically regarded as poor.

METHODS

To evaluate reLT in modern recipients, we retrospectively examined our single-center experience. Analysis included 1268 patients undergoing single LT and 68 patients undergoing reLT from January 2008 to December 2021.

RESULTS

Pre-LT mechanical ventilation, body mass index at LT, donor-recipient ABO incompatibility, early acute rejection, and length of hospitalization were associated with increased risk of needing reLT following index transplant. Overall and graft survival outcomes in the reLT cohort were equivalent to those after single LT. Mortality after reLT was associated with Kidney Donor Profile Index, national organ sharing at reLT, and LT donor death by anoxia and blood urea nitrogen levels. Survival after reLT was independent of the interval between initial LT and reLT, intraoperative packed red blood cell use, cold ischemia time, and preoperative mechanical ventilation, all previously linked to worse outcomes.

CONCLUSIONS

These data suggest that reLT is currently a safer option for patients with liver graft failure, with comparable outcomes to primary LT.

Progress in Combined Liver-lung Transplantation at a Single Center

Combined liver-lung transplantation is an uncommon, although vital, procedure for patients with simultaneous end-stage lung and liver disease. The utility of lung-liver transplant has been questioned because of initial poor survival outcomes, particularly when compared with liver-alone transplant recipients.

Methods

A single-center, retrospective review of the medical records of 19 adult lung-liver transplant recipients was conducted, comparing early recipients (2009-2014) with a recent cohort (2015-2021). Patients were also compared with the center's single lung or liver transplant recipients.

Results

Recent lung-liver recipients were older (P = 0.004), had a higher body mass index (P = 0.03), and were less likely to have ascites (P = 0.02), reflecting changes in the etiologies of lung and liver disease. Liver cold ischemia time was longer in the modern cohort (P = 0.004), and patients had a longer posttransplant length of hospitalization (P = 0.048). Overall survival was not statistically different between the 2 eras studied (P = 0.61), although 1-y survival was higher in the more recent group (90.9% versus 62.5%). Overall survival after lung-liver transplant was equivalent to lung-alone recipients and was significantly lower than liver-alone recipients (5-y survival: 52%, 51%, and 75%, respectively). Lung-liver recipient mortality was primarily driven by deaths within 6 mo of transplant due to infection and sepsis. Graft failure was not significantly different (liver: P = 0.06; lung: P = 0.74).

Conclusions

The severity of illness in lung-liver recipients combined with the infrequency of the procedure supports its continued use. However, particular attention should be paid to patient selection, immunosuppression, and prophylaxis against infection to ensure proper utilization of scarce donor organs.

Hydrodynamics of the fast-start caridoid escape response in Antarctic krill, Euphausia superba

Krill are shrimp-like crustaceans with a high degree of mobility and variety of documented swimming behaviors. The caridoid escape response, a fast-start mechanism unique to crustaceans, occurs when the animal performs a series of rapid abdominal flexions and tail flipping that results in powerful backward strokes. The current results quantify the animal kinematics and three-dimensional flow field around a free-swimming Euphausia superba as it performs the caridoid escape maneuver. The specimen performs a single abdominal flexion-tail flip combination that leads to an acceleration over a 42 ms interval allowing it to reach a maximum speed of 57.0 cm/s (17.3 body lengths/s). The krill's tail flipping during the abdominal closure is a significant contributor to the thrust generation during the maneuver. The krill sheds a complex chain of vortex rings in its wake due to the viscous flow effects while the organism accelerates. The vortex ring structure reveals a strong suction flow in the wake, which suggests that the pressure distribution and form drag play a role in the force balance for this maneuver. Antarctic krill typically swim in a low to intermediate Reynolds number (Re) regime where viscous forces are significant, but as shown by this analysis, its high maneuverability allows it to quickly change its body angle and swimming speed.

Immune Checkpoint Inhibitors for Solid Tumors in the Adjuvant Setting: Current Progress, Future Directions, and Role in Transplant Oncology

The rationale for administering immune checkpoint inhibitors (ICIs) in the adjuvant setting is to eradicate micro-metastases and, ultimately, prolong survival. Thus far, clinical trials have demonstrated that 1-year adjuvant courses of ICIs reduce the risk of recurrence in melanoma, urothelial cancer, renal cell carcinoma, non-small cell lung cancer, and esophageal and gastroesophageal junction cancers. Overall survival benefit has been shown in melanoma while survival data are still not mature in other malignancies. Emerging data also show the feasibility of utilizing ICIs in the peri-transplant setting for hepatobiliary malignancies. While ICIs are generally well-tolerated, the development of chronic immune-related adverse events, typically endocrinopathies or neurotoxicities, as well as delayed immune-related adverse events, warrants further scrutiny regarding the optimal duration of adjuvant therapy and requires a thorough risk-benefit determination. The advent of blood-based, dynamic biomarkers such as circulating tumor DNA (ctDNA) can help detect minimal residual disease and identify the subset of patients who would likely benefit from adjuvant treatment. In addition, the characterization of tumor-infiltrating lymphocytes, neutrophil-to-lymphocyte ratio, and ctDNA-adjusted blood tumor mutation burden (bTMB) has also shown promise in predicting response to immunotherapy. Until additional, prospective studies delineate the magnitude of overall survival benefit and validate the use of predictive biomarkers, a tailored, patient-centered approach to adjuvant ICIs that includes extensive patient counseling on potentially irreversible adverse effects should be routinely incorporated into clinical practice.

Intrahepatic cholangiocarcinoma: The role of liver transplantation, adjunctive treatments, and prognostic biomarkers

Intrahepatic cholangiocarcinoma (iCCA) is a primary epithelial cell malignancy of the liver with rising incidence rate globally. Its insidious presentation, heterogeneous and aggressive biology, and recalcitrance to current therapies results in unacceptably high morbidity and mortality. This has spurred research efforts in the last decade to better characterize it molecularly with translation to improved diagnostic tools and treatments. Much of this has been driven by patient advocacy. This has renewed interest in orthotopic liver transplantation (LT) with adjunctive therapies for iCCA, which was historically disparaged due to poor recipient outcomes and donor organ scarcity. However, the optimal use of LT as a treatment for iCCA care remains unclear. Here, we review the epidemiology of iCCA, the history of LT as a treatment modality, alternative approaches to iCCA local control, the evidence for peri-operative systemic therapies, and the potential roles of biomarkers and targeted agents. In doing so, we hope to prioritize areas for continued research and identify areas where multidisciplinary care can improve outcomes.

Pancreatic cancer evolution and heterogeneity: integrating omics and clinical data

Pancreatic ductal adenocarcinoma (PDAC), already among the deadliest epithelial malignancies, is rising in both incidence and contribution to overall cancer deaths. Decades of research have improved our understanding of PDAC carcinogenesis, including characterizing germline predisposition, the cell of origin, precursor lesions, the sequence of genetic alterations, including simple and structural alterations, transcriptional changes and subtypes, tumour heterogeneity, metastatic progression and the tumour microenvironment. These fundamental advances inform contemporary translational efforts in primary prevention, screening and early detection, multidisciplinary management and survivorship, as prospective clinical trials begin to adopt molecular-based selection criteria to guide targeted therapies. Genomic and transcriptomic data on PDAC were also included in the international pan-cancer analysis of approximately 2,600 cancers, a milestone in cancer research that allows further insight through comparison with other tumour types. Thus, this is an ideal time to review our current knowledge of PDAC evolution and heterogeneity, gained from the study of preclinical models and patient biospecimens, and to propose a model of PDAC evolution that takes into consideration findings from varied sources, with a particular focus on the genomics of human PDAC.

Impact of Research Training on Performance in General Surgery Residency

INTRODUCTION

It is common for North American surgical trainees to interrupt clinical training to complete 2 or more years of research training. The impact of this practice on surgical aptitudes is unknown. The University of Toronto has large general surgery and surgeon scientist training programs. We compared the examination scores of general surgery residents in continuous clinical training with those of residents whose training was interrupted by research.

METHODS

We collected anonymized scores obtained at written and oral annual in-training examinations by general surgery residents at the University of Toronto from 2011 to 2016, inclusive. The written exam assessed knowledge, while the oral exam assessed judgment. Residents were dichotomized into continuous versus non-continuous clinical training streams. We compared performance prior to, during, and following divergence for research training both within and between the 2 groups.

RESULTS

At the junior resident level, future enrollment in research training was associated with higher examination performance (P_written = .003). Annual scores plateaued during research training, while scores of residents who continued in continuous clinical training improved year over year (P_written = .009). Non-continuous stream resident exam scores remained stagnant after 1 year then improved in the second year after return to clinical training (P_written = .00007). Scores obtained in the final year of residency training did not significantly differ between residents who underwent continuous versus non-continuous clinical training. Results from written and oral exams trended concordantly.

CONCLUSIONS

We demonstrate that interruption of clinical training for 2 or more years of research is associated with a stagnation of performance on annual in-training examinations assessing both knowledge and judgment. This phenomenon is followed by an eventual catching-up after at least 2 years return to full-time clinical training. This may inform residency program curriculum design.

Decreased graft loss following implementation of the kidney allocation score (KAS)

BACKGROUND

The Kidney Allocation System (KAS) was developed to improve equity and utility in organ allocation. We examine the effect of this change on kidney graft distribution and survival.

METHODS

UNOS data was used to identify first-time adult recipients of a deceased donor kidney-alone transplant pre-KAS (Jan 2012-Dec 2014, n = 26,612) and post-KAS (Jan 2015-Dec 2017, n = 30,701), as well as grafts recovered Jan 2012-Jun 2019.

RESULTS

Post-KAS, kidneys were more likely to experience cold ischemia time >24 h (20.0% vs. 18.8%, p < 0.001) and experienced more delayed graft function, though competing risks modeling demonstrated a lower hazard of graft loss post-KAS, HR 0.90 (95% CI 0.84-0.97, p = 0.007). Post-policy, KDPI >85% kidneys were more likely to be shared regionally (37% vs. 14%), and more likely to be discarded (60.6% vs. 54.9%) after the policy change. KDPI >85% graft and patient survival did not change.

CONCLUSIONS

Implementation of the KAS has increased sharing of high-KDPI kidneys and has decreased the hazard of graft loss without an impact on patient survival.

Author Correction: Transcription phenotypes of pancreatic cancer are driven by genomic events during tumor evolution

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1-3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10-18.

Transcription phenotypes of pancreatic cancer are driven by genomic events during tumor evolution

Pancreatic adenocarcinoma presents as a spectrum of a highly aggressive disease in patients. The basis of this disease heterogeneity has proved difficult to resolve due to poor tumor cellularity and extensive genomic instability. To address this, a dataset of whole genomes and transcriptomes was generated from purified epithelium of primary and metastatic tumors. Transcriptome analysis demonstrated that molecular subtypes are a product of a gene expression continuum driven by a mixture of intratumoral subpopulations, which was confirmed by single-cell analysis. Integrated whole-genome analysis uncovered that molecular subtypes are linked to specific copy number aberrations in genes such as mutant KRAS and GATA6. By mapping tumor genetic histories, tetraploidization emerged as a key mutational process behind these events. Taken together, these data support the premise that the constellation of genomic aberrations in the tumor gives rise to the molecular subtype, and that disease heterogeneity is due to ongoing genomic instability during progression.

Integration of Genomic and Transcriptional Features in Pancreatic Cancer Reveals Increased Cell Cycle Progression in Metastases

We integrated clinical, genomic, and transcriptomic data from 224 primaries and 95 metastases from 289 patients to characterize progression of pancreatic ductal adenocarcinoma (PDAC). Driver gene alterations and mutational and expression-based signatures were preserved, with truncations, inversions, and translocations most conserved. Cell cycle progression (CCP) increased with sequential inactivation of tumor suppressors, yet remained higher in metastases, perhaps driven by cell cycle regulatory gene variants. Half of the cases were hypoxic by expression markers, overlapping with molecular subtypes. Paired tumor heterogeneity showed cancer cell migration by Halstedian progression. Multiple PDACs arising synchronously and metachronously in the same pancreas were actually intra-parenchymal metastases, not independent primary tumors. Established clinical co-variates dominated survival analyses, although CCP and hypoxia may inform clinical practice.

Reflex Testing for Germline BRCA1, BRCA2, PALB2, and ATM Mutations in Pancreatic Cancer: Mutation Prevalence and Clinical Outcomes From Two Canadian Research Registries

Purpose

We investigated the translational value of reflex testing for germline mutations in four homology-directed DNA repair predisposition genes ( BRCA1, BRCA2, PALB2, and ATM) in consecutive patients with pancreatic adenocarcinoma.

Methods

One hundred fifty patients with French-Canadian (FC) ancestry were evaluated for founder mutations, and 114 patients were subsequently assessed by full gene sequencing and multiplex ligation-dependent probe amplification for nonfounder mutations. Two hundred thirty-six patients unselected for ancestry were also assessed for mutations by full gene sequencing.

Results

The FC founder mutation prevalence among the 150 patients was 5.3% (95% CI, 2.6% to 10.3%), and the nonfounder mutation prevalence across the four genes among the 114 patients tested was 2.6% (95% CI, 0.6% to 7.8%). In the case series unselected for ancestry, 10.0% (95% CI, 2.7% to 26.4%) of patients reporting Ashkenazi Jewish (AJ) ancestry carried an AJ founder mutation, with no nonfounder mutations identified. The mutation prevalence among patients without FC/AJ ancestry was 4.9% (95% CI, 2.6% to 8.8%). Mutations were more frequent in patients diagnosed at ≤ 50 years of age ( P = .03) and in patients with either two or more first- or second-degree relatives with pancreas, breast, ovarian or prostate cancer, or one such relative and a second primary of one of these cancer types ( P < .001). BRCA1, BRCA2, and PALB2 carriers with late-stage (III or IV) disease had an overall survival advantage ( P = .049), particularly if treated with platinum-based chemotherapies ( P = .030).

Conclusion

Considering these results, we recommend reflex founder mutation testing of patients with FC/AJ ancestry and full gene sequencing of patients who are ≤ 50 years or meet the identified family history criteria. Reflex testing of all incident patients for these four genes may become justified as full gene sequencing costs decline.

Mutations in Mitochondrial DNA From Pancreatic Ductal Adenocarcinomas Associate With Survival Times of Patients and Accumulate as Tumors Progress

Somatic mutations have been found in the mitochondria in different types of cancer cells, but it is not clear whether these affect tumorigenesis or tumor progression. We analyzed mitochondrial genomes of 268 early-stage, resected pancreatic ductal adenocarcinoma tissues and paired non-tumor tissues. We defined a mitochondrial somatic mutation (mtSNV) as a position where the difference in heteroplasmy fraction between tumor and normal sample was ≥0.2. Our analysis identified 304 mtSNVs, with at least 1 mtSNV in 61% (164 of 268) of tumor samples. The noncoding control region had the greatest proportion of mtSNVs (60 of 304 mutations); this region contains sites that regulate mitochondrial DNA transcription and replication. Frequently mutated genes included ND5, RNR2, and CO1, plus 29 mutations in transfer RNA genes. mtSNVs in 2 separate mitochondrial genes (ND4 and ND6) were associated with shorter overall survival time. This association appeared to depend on the level of mtSNV heteroplasmy. Non-random co-occurrence between mtSNVs and mutations in nuclear genes indicates interactions between nuclear and mitochondrial DNA. In an analysis of primary tumors and metastases from 6 patients, we found tumors to accumulate mitochondrial mutational mutations as they progress.

Exome-Wide Association Study of Pancreatic Cancer Risk

We conducted a case-control exome-wide association study to discover germline variants in coding regions that affect risk for pancreatic cancer, combining data from 5 studies. We analyzed exome and genome sequencing data from 437 patients with pancreatic cancer (cases) and 1922 individuals not known to have cancer (controls). In the primary analysis, BRCA2 had the strongest enrichment for rare inactivating variants (17/437 cases vs 3/1922 controls) (P = 3.27x10-6; exome-wide statistical significance threshold P < 2.5x10-6). Cases had more rare inactivating variants in DNA repair genes than controls, even after excluding 13 genes known to predispose to pancreatic cancer (adjusted odds ratio, 1.35; P = .045). At the suggestive threshold (P < .001), 6 genes were enriched for rare damaging variants (UHMK1, AP1G2, DNTA, CHST6, FGFR3, and EPHA1) and 7 genes had associations with pancreatic cancer risk, based on the sequence-kernel association test. We confirmed variants in BRCA2 as the most common high-penetrant genetic factor associated with pancreatic cancer and we also identified candidate pancreatic cancer genes. Large collaborations and novel approaches are needed to overcome the genetic heterogeneity of pancreatic cancer predisposition.

Genomics-Driven Precision Medicine for Advanced Pancreatic Cancer: Early Results from the COMPASS Trial

Purpose: To perform real-time whole genome sequencing (WGS) and RNA sequencing (RNASeq) of advanced pancreatic ductal adenocarcinoma (PDAC) to identify predictive mutational and transcriptional features for better treatment selection.Experimental Design: Patients with advanced PDAC were prospectively recruited prior to first-line combination chemotherapy. Fresh tumor tissue was acquired by image-guided percutaneous core biopsy for WGS and RNASeq. Laser capture microdissection was performed for all cases. Primary endpoint was feasibility to report WGS results prior to first disease assessment CT scan at 8 weeks. The main secondary endpoint was discovery of patient subsets with predictive mutational and transcriptional signatures.Results: Sixty-three patients underwent a tumor biopsy between December 2015 and June 2017. WGS and RNASeq were successful in 62 (98%) and 60 (95%), respectively. Genomic results were reported at a median of 35 days (range, 19-52 days) from biopsy, meeting the primary feasibility endpoint. Objective responses to first-line chemotherapy were significantly better in patients with the classical PDAC RNA subtype compared with those with the basal-like subtype (P = 0.004). The best progression-free survival was observed in those with classical subtype treated with m-FOLFIRINOX. GATA6 expression in tumor measured by RNA in situ hybridization was found to be a robust surrogate biomarker for differentiating classical and basal-like PDAC subtypes. Potentially actionable genetic alterations were found in 30% of patients.Conclusions: Prospective genomic profiling of advanced PDAC is feasible, and our early data indicate that chemotherapy response differs among patients with different genomic/transcriptomic subtypes. Clin Cancer Res; 24(6); 1344-54. ©2017 AACR.

Next generation sequencing of pancreatic ductal adenocarcinoma: right or wrong?

Pancreatic ductal adenocarcinoma (PDAC) has the highest mortality rate of all epithelial malignancies and a paradoxically rising incidence rate. Clinical translation of next generation sequencing (NGS) of tumour and germline samples may ameliorate outcomes by identifying prognostic and predictive genomic and transcriptomic features in appreciable fractions of patients, facilitating enrolment in biomarker-matched trials. Areas covered: The literature on precision oncology is reviewed. It is found that outcomes may be improved across various malignancies, and it is suggested that current issues of adequate tissue acquisition, turnaround times, analytic expertise and clinical trial accessibility may lessen as experience accrues. Also reviewed are PDAC genomic and transcriptomic NGS studies, emphasizing discoveries of promising biomarkers, though these require validation, and the fraction of patients that will benefit from these outside of the research setting is currently unknown. Expert commentary: Clinical use of NGS with PDAC should be used in investigational contexts in centers with multidisciplinary expertise in cancer sequencing and pancreatic cancer management. Biomarker directed studies will improve our understanding of actionable genomic variation in PDAC, and improve outcomes for this challenging disease.

Association of Distinct Mutational Signatures With Correlates of Increased Immune Activity in Pancreatic Ductal Adenocarcinoma

IMPORTANCE

Outcomes for patients with pancreatic ductal adenocarcinoma (PDAC) remain poor. Advances in next-generation sequencing provide a route to therapeutic approaches, and integrating DNA and RNA analysis with clinicopathologic data may be a crucial step toward personalized treatment strategies for this disease.

OBJECTIVE

To classify PDAC according to distinct mutational processes, and explore their clinical significance.

DESIGN, SETTING, AND PARTICIPANTS

We performed a retrospective cohort study of resected PDAC, using cases collected between 2008 and 2015 as part of the International Cancer Genome Consortium. The discovery cohort comprised 160 PDAC cases from 154 patients (148 primary; 12 metastases) that underwent tumor enrichment prior to whole-genome and RNA sequencing. The replication cohort comprised 95 primary PDAC cases that underwent whole-genome sequencing and expression microarray on bulk biospecimens.

MAIN OUTCOMES AND MEASURES

Somatic mutations accumulate from sequence-specific processes creating signatures detectable by DNA sequencing. Using nonnegative matrix factorization, we measured the contribution of each signature to carcinogenesis, and used hierarchical clustering to subtype each cohort. We examined expression of antitumor immunity genes across subtypes to uncover biomarkers predictive of response to systemic therapies.

RESULTS

The discovery cohort was 53% male (n = 79) and had a median age of 67 (interquartile range, 58-74) years. The replication cohort was 50% male (n = 48) and had a median age of 68 (interquartile range, 60-75) years. Five predominant mutational subtypes were identified that clustered PDAC into 4 major subtypes: age related, double-strand break repair, mismatch repair, and 1 with unknown etiology (signature 8). These were replicated and validated. Signatures were faithfully propagated from primaries to matched metastases, implying their stability during carcinogenesis. Twelve of 27 (45%) double-strand break repair cases lacked germline or somatic events in canonical homologous recombination genes-BRCA1, BRCA2, or PALB2. Double-strand break repair and mismatch repair subtypes were associated with increased expression of antitumor immunity, including activation of CD8-positive T lymphocytes (GZMA and PRF1) and overexpression of regulatory molecules (cytotoxic T-lymphocyte antigen 4, programmed cell death 1, and indolamine 2,3-dioxygenase 1), corresponding to higher frequency of somatic mutations and tumor-specific neoantigens.

CONCLUSIONS AND RELEVANCE

Signature-based subtyping may guide personalized therapy of PDAC in the context of biomarker-driven prospective trials.

Molecular Events in the Natural History of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest epithelial malignancies. Improvements in our understanding of PDAC carcinogenesis will hopefully improve its detection, management, and outcomes, as has been achieved with other malignancies. Here we review the literature on the natural history of PDAC, including its cell of origin, the initiating somatic mutational events, pathways deranged in the mature tumor, its biological heterogeneity, and the relationship of the primary tumor with metastases. We also suggest areas for further research and highlight translatable findings that are beginning to make clinical inroads.

Abstract A23: Rare variants in the FAT1 gene may predispose to familial colorectal cancer

Introduction: Population- and family-based studies suggest germline predisposition in up to 35% of colorectal cancer (CRC) cases. Known genetic factors, including three highly penetrant Mendelian cancer syndromes and approximately 45 low penetrant alleles, account for less than 15% of all CRC and only a small proportion of early onset CRC. Identifying the genes responsible for the “missing” CRC predisposition will inform prevention and management.

Methods: Our discovery cohort were selected to enrich for likely heritable susceptibility and consisted of 127 CRC cases from 86 pedigrees selected from Canadian and Australian CRC Family Registries (CCFRs) that met the Familial Colorectal Cancer Type X definition (satisfy Amsterdam I Criteria and lack other features of known cancer syndromes). Germline DNA from multiple CRC–affected individuals per pedigree underwent whole exome sequencing. The two replication cohorts were composed of pedigrees with multiple generations affected by CRC, one an Australian cohort of 166 families from which multiple affected and unaffected members were genotyped for rare (&lt;0.01 MAF) germline likely deleterious variants in FAT1, the other a Polish cohort of 496 probands that underwent targeted next generation sequencing of FAT1. Alignment and variant calling followed the Genome Analysis Tool Kit “best practices”, and ANNOVAR was used for functional effect, allele frequency and intolerance score annotations. Variant filtering and statistical analysis were done in R (version 3.0). A hemizygous transgenic mouse model of our top genetic candidate was developed and exposed to intra-peritoneal azoxymethane (AOM) to induce colonic dysplasia. Necropsies were performed at 6 months of age, and the colons underwent gross and histologic inspection. This work was supported by grant UM1 CA167551 from the National Cancer Institute (NCI) to the Colon Cancer Family Registry.

Outcomes: Using filter-based approaches in our discovery cohort, we identified rare, non-silent variants in FAT1 that co-segregated with CRC in Ontario (Canadian), Newfoundland (Canadian) and Australian pedigrees, including one stopgain variant that was found in all 4 affected of one Ontario pedigree and in 2 of 6 unaffected. Somatic loss of heterozygosity of FAT1 was seen in available FFPE tumors from 3 Ontario and 4 Australian pedigrees by either Sanger sequencing or microarray. Modified segregation analysis of genotyped multi-case families from the Australian CCFR demonstrated an overall increased risk for CRC in FAT1 carriers (HR 1.44, 95%CI 1.05-1.97), with greater hazard ratios (&gt;2.5) for individual FAT1 variants identified in sufficient numbers of families. Deep sequencing in 496 Polish probands identified 4 additional rare truncating FAT1 variants. Using the ExAC database as controls, variant-level association analyses of the Polish cohort cases revealed two strongly predisposing FAT1 rare missense variants, namely c.T9440G (OR 7.53, 95%CI 4.1-12.8, Fisher's exact test, q &lt; 0.05 by false discovery rates) and c.G3067A (OR 10.8, 95%CI 3.3-26.8, q &lt; 0.05). Gene-level association testing was also significant for increased CRC risk when considering all rare, non-silent FAT1 variants (OR 2.2, 95%CI 1.8-2.6, q &lt; 0.05). 30 FAT1 hemizygous and 28 wild type mice on a CD1 background, balanced for sex and weight, did not show differences in number or greatest size of aberrant crypts, adenoma or adenocarcinoma.

Conclusions: We have shown that rare germline variants in FAT1 may predispose to CRC. Discovery of such causal genes and associated pathways will improve our understanding of early onset CRC for both familial and sporadic cases. Stratifying CRC risk by familial susceptibility genes should foster tailored, cost-effective primary and secondary prevention strategies.

Citation Format: Ashton A. Connor, Jordan Lerner-Ellis, Mohammad R. Akbari, Cezary Cybulski, J Lubinski, Caroline Badouel, Helen McNeill, James G. Dowty, Mark Clendenning, Daniel D. Buchanan. Rare variants in the FAT1 gene may predispose to familial colorectal cancer. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A23.

A renewed model of pancreatic cancer evolution based on genomic rearrangement patterns

Pancreatic cancer, a highly aggressive tumour type with uniformly poor prognosis, exemplifies the classically held view of stepwise cancer development. The current model of tumorigenesis, based on analyses of precursor lesions, termed pancreatic intraepithelial neoplasm (PanINs) lesions, makes two predictions: first, that pancreatic cancer develops through a particular sequence of genetic alterations (KRAS, followed by CDKN2A, then TP53 and SMAD4); and second, that the evolutionary trajectory of pancreatic cancer progression is gradual because each alteration is acquired independently. A shortcoming of this model is that clonally expanded precursor lesions do not always belong to the tumour lineage, indicating that the evolutionary trajectory of the tumour lineage and precursor lesions can be divergent. This prevailing model of tumorigenesis has contributed to the clinical notion that pancreatic cancer evolves slowly and presents at a late stage. However, the propensity for this disease to rapidly metastasize and the inability to improve patient outcomes, despite efforts aimed at early detection, suggest that pancreatic cancer progression is not gradual. Here, using newly developed informatics tools, we tracked changes in DNA copy number and their associated rearrangements in tumour-enriched genomes and found that pancreatic cancer tumorigenesis is neither gradual nor follows the accepted mutation order. Two-thirds of tumours harbour complex rearrangement patterns associated with mitotic errors, consistent with punctuated equilibrium as the principal evolutionary trajectory. In a subset of cases, the consequence of such errors is the simultaneous, rather than sequential, knockout of canonical preneoplastic genetic drivers that are likely to set-off invasive cancer growth. These findings challenge the current progression model of pancreatic cancer and provide insights into the mutational processes that give rise to these aggressive tumours.

Genetic testing for Lynch syndrome in the province of Ontario

BACKGROUND

In November 2001, genetic testing for Lynch syndrome (LS) was introduced by the Ministry of Health and Long-Term Care (MOH) in Ontario for individuals at high risk for LS cancers according to either tumor immunohistochemistry staining or their family history. This article describes the outcomes of the program and makes recommendations for improving it and informing other public health care programs.

METHODS

Subjects were referred for molecular testing of the mismatch repair (MMR) genes MutL homolog 1, MutS homolog 2, and MutS homolog 6 if they met 1 of 7 MOH criteria. Testing was conducted from January 2001 to March 2015 at the Molecular Diagnostic Laboratory of Mount Sinai Hospital in Toronto.

RESULTS

A total of 1452 subjects were tested. Of the 662 subjects referred for testing because their tumor was immunodeficient for 1 or more of the MMR genes, 251 (37.9%) carried a germline mutation. In addition, 597 subjects were tested for a known family mutation, and 298 (49.9%) were positive; 189 of these 298 subjects (63.4%) were affected with cancer at the time of testing. An additional 193 subjects were referred because of a family history of LS, and 34 of these (17.6%) had a mutation identified.

CONCLUSIONS

These results indicate that the provincial criteria are useful in identifying LS carriers after an MMR-deficient tumor is identified. Placing greater emphasis on testing unaffected relatives in families with a known mutation may identify more unaffected carriers and facilitate primary prevention in those individuals. Cancer 2016;122:1672-9. © 2016 American Cancer Society.

Central, But Not Peripheral, Circulating Tumor Cells are Prognostic in Patients Undergoing Resection of Colorectal Cancer Liver Metastases

BACKGROUND

Colorectal cancer liver metastases (CRLMs) are potentially curable with resection, but most patients recur and succumb to their disease. Clinical covariates do not account for all outcomes. Circulating tumor cells (CTCs) are prognostic in the primary and metastatic settings of breast, prostate and colorectal cancer (CRC), and evolving evidence supports their role in CRLMs. Our objective was to determine whether CTCs in peripheral (PV) and hepatic venous (HV) compartments are associated with disease-free survival (DFS) and overall survival (OS) post-CRLM resection.

METHODS

CTCs were measured by CellSearch assay from intraoperative HV and PV samples from 63 patients who underwent CRLM resection from June 2007 to August 2012 at a single center. DFS and OS were primary endpoints.

RESULTS

HV CTCs > 3 were associated with shorter DFS and OS, but not PV CTCs, although no significant difference was found between CTC measurements in the two compartments. By univariate analysis, CRC stage and site, CRLM recurrence, and hepatic capsule invasion were also associated with OS, but only HV CTCs and CRC site were significant by multivariate Cox. Only HV CTCs were associated with DFS by multivariate analysis. Cases with elevated HV CTCs had hepatic vein invasion and lymph node metastases, and were younger with larger tumors.

CONCLUSIONS

Elevated HV CTCs are prognostic for DFS and OS following CRLM resection. Clinicopathologic features associated with HV CTCs are identifiable preoperatively and should be considered in CRLM surgical decision making. We found no evidence that PV CTCs are prognostic in this setting.

Abstract A1-17: Genomic analysis of metachronous pancreatic ductal adenocarcinoma

Background: Improving outcomes for pancreatic ductal adenocarcinoma (PDAC) requires more complete understanding of pancreatic carcinogenesis, including tumor heterogeneity and mutational evolution. Such studies in PDAC are hampered by presentation at advanced stages and rarely operable recurrences. We present a case of metachronous PDAC managed by serial resections and interrogated by whole genome sequencing of all three lesions.

Methods: Tumors underwent either laser capture microscopy or flow cytometry of fresh frozen tissue. Germline DNA was obtained from normal tissue. Genomic DNA was isolated, and sequencing libraries were prepared. Whole genome sequencing was performed on the Illumina HiSeq2500 system. Pipeline analysis included quality control, alignment to the reference genome (hg19), variant calling and annotation. Structural variants were called by the union of two tools, DELLY and CREST. Copy number variants were called using an in-house tool. Single nucleotide polymorphisms and short insertions and deletions were identified by the intersection of two tools, Strelka and MuTect, and annotated using ANNOVAR. All structural, copy number and non-silent variants were manually reviewed in the Integrated Genome Viewer. Secondary analyses were done in R. Representative sections of the three tumors also underwent formalin fixation, paraffin embedding, sectioning at five micron thickness and hematoxylin and eosin staining for microscopic analysis.

Results: The first tumor was located in the head of the pancreas and resected by Whipple operation, the second and third in the body and tail, respectively, and resected by completion pancreatectomy 14 months later. The patient received chemotherapy in the interim.

Histologically, all 3 tumors were moderately differentiated adenocarcinomas with focal mucinous areas and extensive lymphovascular and perineural invasion. There were no distinguishing morphological features.

For the 3 lesions, we achieved average sequence coverage of 52.3x, 54.3x, and 70.7x, respectively.

A total of 69 structural variants and 62 copy number variants were identified, with concordance of 75% and 92% in all three lesions.

A total of 61 non-silent exonic variants were identified, with concordance of 33% in all three lesions. A KRAS (NM_004985) c.G34C missense and TP53 (NM_001126115) c.G418A missense were present in all three, whereas a SMAD4 (NM_005359) c.118delC frameshift was present in only the second and third tumors.

Hierarchical clustering by non-silent variants, copy number variants, and an intersect of all variants showed the tumors in the head and tail to be more closely related to one another than to the body lesion, whereas clustering by structural variants showed little difference between the three.

Conclusions: The highly similar structural and copy number profiles across the three lesions suggests that these tumors arose from a common precursor, and that large chromosomal changes occurred early in its mutational evolution.

The poor concordance of simple somatic mutations imply that these evolved gradually and are responsible for tumor heterogeneity and possibly acquired phenotypes, include therapeutic resistance.

This study also demonstrates that isolated, intra-parenchymal metastases (as opposed to de novo tumors within a “field defect”) are possible with PDAC, which has been suggested in case reports but never definitively proven, further implying that these patients may benefit from re-operation despite disease relapse.

Further analysis will include mathematical modeling of mutation rates and validation in three additional metachronous cases identified in our biospecimen repository and in specimens obtained by our rapid autopsy program.

Citation Format: Ashton A. Connor, Michelle Chan-Seng-Yue, Robert E. Denroche, Ayelet Borgida, Sheng-Ben Liang, Faiyaz Notta, Lincoln Stein, Michael H. Roehrl, John McPherson, Steven Gallinger. Genomic analysis of metachronous pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr A1-17.

Abstract B2-57: Genomic analysis of metachronous pancreatic ductal adenocarcinoma

Background: Improving outcomes for pancreatic ductal adenocarcinoma (PDAC) requires more complete understanding of pancreatic carcinogenesis, including tumor heterogeneity and mutational evolution. Such studies in PDAC are hampered by presentation at advanced stages and rarely operable recurrences. We present a case of metachronous PDAC managed by serial resections and interrogated by whole genome sequencing of all three lesions.

Methods: Tumors underwent either laser capture microscopy or flow cytometry of fresh frozen tissue. Germline DNA was obtained from normal tissue. Genomic DNA was isolated, and sequencing libraries were prepared. Whole genome sequencing was performed on the Illumina HiSeq2500 system. Pipeline analysis included quality control, alignment to the reference genome (hg19), variant calling and annotation. Structural variants were called by the union of two tools, DELLY and CREST. Copy number variants were called using an in-house tool. Single nucleotide polymorphisms and short insertions and deletions were identified by the intersection of two tools, Strelka and MuTect, and annotated using ANNOVAR. All structural, copy number and non-silent variants were manually reviewed in the Integrated Genome Viewer. Secondary analyses were done in R. Representative sections of the three tumors also underwent formalin fixation, paraffin embedding, sectioning at five micron thickness and hematoxylin and eosin staining for microscopic analysis.

Results: The first tumor was located in the head of the pancreas and resected by Whipple operation, the second and third in the body and tail, respectively, and resected by completion pancreatectomy 14 months later. The patient received chemotherapy in the interim.

Histologically, all 3 tumors were moderately differentiated adenocarcinomas with focal mucinous areas and extensive lymphovascular and perineural invasion. There were no distinguishing morphological features.

For the 3 lesions, we achieved average sequence coverage of 52.3x, 54.3x, and 70.7x, respectively.

A total of 69 structural variants and 62 copy number variants were identified, with concordance of 75% and 92% in all three lesions.

A total of 61 non-silent exonic variants were identified, with concordance of 33% in all three lesions. A KRAS (NM_004985) c.G34C missense and TP53 (NM_001126115) c.G418A missense were present in all three, whereas a SMAD4 (NM_005359) c.118delC frameshift was present in only the second and third tumors.

Hierarchical clustering by non-silent variants, copy number variants, and an intersect of all variants showed the tumors in the head and tail to be more closely related to one another than to the body lesion, whereas clustering by structural variants showed little difference between the three.

Conclusions: The highly similar structural and copy number profiles across the three lesions suggests that these tumors arose from a common precursor, and that large chromosomal changes occurred early in its mutational evolution.

The poor concordance of simple somatic mutations imply that these evolved gradually and are responsible for tumor heterogeneity and possibly acquired phenotypes, include therapeutic resistance.

This study also demonstrates that isolated, intra-parenchymal metastases (as opposed to de novo tumors within a “field defect”) are possible with PDAC, which has been suggested in case reports but never definitively proven, further implying that these patients may benefit from re-operation despite disease relapse.

Further analysis will include mathematical modeling of mutation rates and validation in three additional metachronous cases identified in our biospecimen repository and in specimens obtained by our rapid autopsy program.

Citation Format: Ashton A. Connor, Michelle Chan-Seng-Yue, Robert E. Denroche, Ayelet Borgida, Sheng-Ben Liang, Faiyaz Notta, Lincoln Stein, Michael H. Roehrl, John McPherson, Steven Gallinger. Genomic analysis of metachronous pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Computational and Systems Biology of Cancer; Feb 8-11 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 2):Abstract nr B2-57.

Hereditary Pancreatic Cancer Syndromes

Despite decades of scientific and clinical research, pancreatic ductal adenocarcinoma (PDAC) remains a lethal malignancy. The clinical and pathologic features of PDAC, specifically the known environmental and genetic risk factors, are reviewed here with special emphasis on the hereditary pancreatic cancer (HPC) syndromes. For these latter conditions, strategies are described for their identification, for primary and secondary prevention in unaffected carriers, and for disease management in affected carriers. Nascent steps have been made toward personalized medicine based on the rational use of screening, tumor subtyping, and targeted therapies; these have been guided by growing knowledge of HPC syndromes in PDAC.

Prevalence of germline mutations in cancer predisposition genes in patients with pancreatic cancer

BACKGROUND & AIMS

We investigated the prevalence of germline mutations in APC, ATM, BRCA1, BRCA2, CDKN2A, MLH1, MSH2, MSH6, PALB2, PMS2, PRSS1, STK11, and TP53 in patients with pancreatic cancer.

METHODS

The Ontario Pancreas Cancer Study enrolls consenting participants with pancreatic cancer from a province-wide electronic pathology database; 708 probands were enrolled from April 2003 through August 2012. To improve the precision of BRCA2 prevalence estimates, 290 probands were selected from 3 strata, based on family history of breast and/or ovarian cancer, pancreatic cancer, or neither. Germline DNA was analyzed by next-generation sequencing using a custom multiple-gene panel. Mutation prevalence estimates were calculated from the sample for the entire cohort.

RESULTS

Eleven pathogenic mutations were identified: 3 in ATM, 1 in BRCA1, 2 in BRCA2, 1 in MLH1, 2 in MSH2, 1 in MSH6, and 1 in TP53. The prevalence of mutations in all 13 genes was 3.8% (95% confidence interval, 2.1%-5.6%). Carrier status was associated significantly with breast cancer in the proband or first-degree relative (P < .01), and with colorectal cancer in the proband or first-degree relative (P < .01), but not family history of pancreatic cancer, age at diagnosis, or stage at diagnosis. Of patients with a personal or family history of breast and colorectal cancer, 10.7% (95% confidence interval, 4.4%-17.0%) and 11.1% (95% confidence interval, 3.0%-19.1%) carried pathogenic mutations, respectively.

CONCLUSIONS

A small but clinically important proportion of pancreatic cancer is associated with mutations in known predisposition genes. The heterogeneity of mutations identified in this study shows the value of using a multiple-gene panel in pancreatic cancer.