Adeno-associated virus as a delivery vector for gene therapy of human diseases.

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

Death after High-Dose rAAV9 Gene Therapy in a Patient with Duchenne's Muscular Dystrophy.

We treated a 27-year-old patient with Duchenne's muscular dystrophy (DMD) with recombinant adeno-associated virus (rAAV) serotype 9 containing dSaCas9 (i.e., "dead" Staphylococcus aureus Cas9, in which the Cas9 nuclease activity has been inactivated) fused to VP64; this transgene was designed to up-regulate cortical dystrophin as a custom CRISPR-transactivator therapy. The dose of rAAV used was 1×1014 vector genomes per kilogram of body weight. Mild cardiac dysfunction and pericardial effusion developed, followed by acute respiratory distress syndrome (ARDS) and cardiac arrest 6 days after transgene treatment; the patient died 2 days later. A postmortem examination showed severe diffuse alveolar damage. Expression of transgene in the liver was minimal, and there was no evidence of AAV serotype 9 antibodies or effector T-cell reactivity in the organs. These findings indicate that an innate immune reaction caused ARDS in a patient with advanced DMD treated with high-dose rAAV gene therapy. (Funded by Cure Rare Disease.).

IL-13 induced inflammation increases DPP4 abundance but does not enhance MERS-CoV replication in airway epithelia.

BACKGROUND: Chronic pulmonary conditions such as asthma and COPD increase the risk of morbidity and mortality during infection with the Middle East respiratory syndrome coronavirus (MERS-CoV). We hypothesized that individuals with such comorbidities are more susceptible to MERS-CoV infection due to increased expression of its receptor, dipeptidyl peptidase 4 (DPP4). METHODS: We modeled chronic airway disease by treating primary human airway epithelia with the Th2 cytokine IL-13, examining how this impacted DPP4 protein levels along with MERS-CoV entry and replication. RESULTS: IL-13 exposure for 3 days led to increased DPP4 protein abundance, while a 21-day treatment increased DPP4 levels and caused goblet cell metaplasia. Surprisingly, despite this increase in receptor availability, MERS-CoV entry and replication were not significantly impacted by IL-13 treatment. CONCLUSIONS: Our results suggest that increased DPP4 abundance is likely not the primary mechanism leading to increased MERS severity in the setting of Th2 inflammation. Transcriptional profiling analysis highlighted the complexity of IL-13 induced changes in airway epithelia, including altered expression of genes involved in innate immunity, antiviral responses, and maintenance of the extracellular mucus barrier. These data suggest that additional factors likely interact with DPP4 abundance to determine MERS-CoV infection outcomes.

Video-Based Communication Assessment of Physician Error Disclosure Skills by Crowdsourced Laypeople and Patient Advocates Who Experienced Medical Harm: Reliability Assessment With Generalizability Theory.

BACKGROUND: Residents may benefit from simulated practice with personalized feedback to prepare for high-stakes disclosure conversations with patients after harmful errors and to meet American Council on Graduate Medical Education mandates. Ideally, feedback would come from patients who have experienced communication after medical harm, but medical researchers and leaders have found it difficult to reach this community, which has made this approach impractical at scale. The Video-Based Communication Assessment app is designed to engage crowdsourced laypeople to rate physician communication skills but has not been evaluated for use with medical harm scenarios. OBJECTIVE: We aimed to compare the reliability of 2 assessment groups (crowdsourced laypeople and patient advocates) in rating physician error disclosure communication skills using the Video-Based Communication Assessment app. METHODS: Internal medicine residents used the Video-Based Communication Assessment app; the case, which consisted of 3 sequential vignettes, depicted a delayed diagnosis of breast cancer. Panels of patient advocates who have experienced harmful medical error, either personally or through a family member, and crowdsourced laypeople used a 5-point scale to rate the residents' error disclosure communication skills (6 items) based on audiorecorded responses. Ratings were aggregated across items and vignettes to create a numerical communication score for each physician. We used analysis of variance, to compare stringency, and Pearson correlation between patient advocates and laypeople, to identify whether rank order would be preserved between groups. We used generalizability theory to examine the difference in assessment reliability between patient advocates and laypeople. RESULTS: Internal medicine residents (n=20) used the Video-Based Communication Assessment app. All patient advocates (n=8) and 42 of 59 crowdsourced laypeople who had been recruited provided complete, high-quality ratings. Patient advocates rated communication more stringently than crowdsourced laypeople (patient advocates: mean 3.19, SD 0.55; laypeople: mean 3.55, SD 0.40; P<.001), but patient advocates' and crowdsourced laypeople's ratings of physicians were highly correlated (r=0.82, P<.001). Reliability for 8 raters and 6 vignettes was acceptable (patient advocates: G coefficient 0.82; crowdsourced laypeople: G coefficient 0.65). Decision studies estimated that 12 crowdsourced layperson raters and 9 vignettes would yield an acceptable G coefficient of 0.75. CONCLUSIONS: Crowdsourced laypeople may represent a sustainable source of reliable assessments of physician error disclosure skills. For a simulated case involving delayed diagnosis of breast cancer, laypeople correctly identified high and low performers. However, at least 12 raters and 9 vignettes are required to ensure adequate reliability and future studies are warranted. Crowdsourced laypeople rate less stringently than raters who have experienced harm. Future research should examine the value of the Video-Based Communication Assessment app for formative assessment, summative assessment, and just-in-time coaching of error disclosure communication skills.

RNPS1 inhibits excessive tumor necrosis factor/tumor necrosis factor receptor signaling to support hematopoiesis in mice.

Null mutations of spliceosome components or cofactors are homozygous lethal in eukaryotes, but viable hypomorphic mutations provide an opportunity to understand the physiological impact of individual splicing proteins. We describe a viable missense allele (F181I) of Rnps1 encoding an essential regulator of splicing and nonsense-mediated decay (NMD), identified in a mouse genetic screen for altered immune cell development. Homozygous mice displayed a stem cell­intrinsic defect in hematopoiesis of all lineages due to excessive apoptosis induced by tumor necrosis factor (TNF)­dependent death signaling. Numerous transcript splice variants containing retained introns and skipped exons were detected at elevated frequencies in Rnps1F181I/F181I splenic CD8+ T cells and hematopoietic stem cells (HSCs), but NMD appeared normal. Strikingly, Tnf knockout rescued all hematopoietic cells to normal or near-normal levels in Rnps1F181I/F181I mice and dramatically reduced intron retention in Rnps1F181I/F181I CD8+ T cells and HSCs. Thus, RNPS1 is necessary for accurate splicing, without which disinhibited TNF signaling triggers hematopoietic cell death.

TRPV4 mutations causing mixed neuropathy and skeletal phenotypes result in severe gain of function.

OBJECTIVE: Distinct dominant mutations in the calcium-permeable ion channel TRPV4 (transient receptor potential vanilloid 4) typically cause nonoverlapping diseases of either the neuromuscular or skeletal systems. However, accumulating evidence suggests that some patients develop mixed phenotypes that include elements of both neuromuscular and skeletal disease. We sought to define the genetic and clinical features of these patients. METHODS: We report a 2-year-old with a novel R616G mutation in TRPV4 with a severe neuropathy phenotype and bilateral vocal cord paralysis. Interestingly, a different substitution at the same residue, R616Q, has been reported in families with isolated skeletal dysplasia. To gain insight into clinical features and potential genetic determinants of mixed phenotypes, we perform in-depth analysis of previously reported patients along with functional and structural assessment of selected mutations. RESULTS: We describe a wide range of neuromuscular and skeletal manifestations and highlight specific mutations that are more frequently associated with overlap syndromes. We find that mutations causing severe, mixed phenotypes have an earlier age of onset and result in more marked elevations of intracellular calcium, increased cytotoxicity, and reduced sensitivity to TRPV4 antagonism. Structural analysis of the two mutations with the most dramatic gain of ion channel function suggests that these mutants likely cause constitutive channel opening through disruption of the TRPV4 S5 transmembrane domain. INTERPRETATION: These findings demonstrate that the degree of baseline calcium elevation correlates with development of mixed phenotypes and sensitivity to pharmacologic channel inhibition, observations that will be critical for the design of future clinical trials for TRPV4 channelopathies.

Effects of Reduced Nicotine Content Cigarettes on Fractional Exhaled Nitric Oxide and Self-Reported Respiratory Health Outcomes Among Smokers With Psychiatric Conditions or Socioeconomic Disadvantage.

INTRODUCTION: This study examined whether exposure to reduced-nicotine-content cigarettes (RNCCs) for 12 weeks alters respiratory health using Fractional Exhaled Nitric Oxide (FeNO), a validated biomarker of respiratory epithelial health, and the Respiratory Health Questionnaire (RHQ), a subject-rated questionnaire on respiratory symptoms. Participants were 747 adult daily smokers enrolled in three double-blind, randomized clinical trials evaluating effects of cigarette nicotine content (0.4, 2.4, 15.8 mg nicotine/g tobacco) in people with affective disorders, opioid use disorder (OUD), or socioeconomic disadvantage. AIMS AND METHODS: FeNO levels and RHQ ratings were collected at baseline and Weeks 6 and 12 following randomization. Multiple regression was used to assess associations of FeNO and RHQ with smoking characteristics. Mixed-model repeated-measures ANOVA was used to evaluate the effects of nicotine content on FeNO and RHQ outcomes over the 12-week study period. RESULTS: FeNO levels but not RHQ ratings varied inversely with smoking characteristics at baseline (Ps < 0.0001) in smokers with affective disorders and socioeconomic disadvantage but less so in those with OUD. Participants with affective disorders and socioeconomic disadvantage, but not those with OUD, who were assigned to RNCCs had higher FeNO levels at Week 12 than those assigned to the 15.8 mg/g dose [F(2,423) = 4.51, p = .01, Cohen's d = 0.21]. No significant dose-related changes in RHQ scores were identified. CONCLUSIONS: Use of RNCCs across a 12-week period attenuates smoking-related reductions in FeNO levels in smokers with affective disorders and socioeconomic disadvantage although not those with OUD. FeNO changes were not accompanied by changes in respiratory-health ratings. TRIAL REGISTRATION: Inclusion and exclusion criteria for the sample and experimental manipulation of the nicotine content of assigned cigarettes are registered: NCT02232737, NCT02250664, NCT02250534. The FeNO measure reported in this manuscript is an exploratory outcome that was not registered. IMPLICATIONS: Should a reduced nicotine content standard be implemented; these results suggest that reduced nicotine content in cigarettes will not exacerbate and instead may attenuate smoking-related decreases in FeNO. This is significant as NO is an important component in maintaining a healthy respiratory system and necessary to defend against infection. Furthermore, the results of the current study demonstrate that the adoption of the reduced nicotine content standard may result in beneficial impacts on respiratory epithelial health among vulnerable populations that are disproportionally affected by the adverse health outcomes precipitated by combustible tobacco use.

Calcium flux control by Pacs1-Wdr37 promotes lymphocyte quiescence and lymphoproliferative diseases.

Endoplasmic reticulum (ER) calcium (Ca2+ ) stores are critical to proteostasis, intracellular signaling, and cellular bioenergetics. Through forward genetic screening in mice, we identified two members of a new complex, Pacs1 and Wdr37, which are required for normal ER Ca2+ handling in lymphocytes. Deletion of Pacs1 or Wdr37 caused peripheral lymphopenia that was linked to blunted Ca2+ release from the ER after antigen receptor stimulation. Pacs1-deficient cells showed diminished inositol triphosphate receptor expression together with increased ER and oxidative stress. Mature Pacs1-/- B cells proliferated and died in vivo under lymphocyte replete conditions, indicating spontaneous loss of cellular quiescence. Disruption of Pacs1-Wdr37 did not diminish adaptive immune responses, but potently suppressed lymphoproliferative disease models by forcing loss of quiescence. Thus, Pacs1-Wdr37 plays a critical role in stabilizing lymphocyte populations through ER Ca2+ handling and presents a new target for lymphoproliferative disease therapy.

Long-Term Impacts Faced by Patients and Families After Harmful Healthcare Events.

BACKGROUND: Patients and families report experiencing a multitude of harms from medical errors resulting in physical, emotional, and financial hardships. Little is known about the duration and nature of these harms and the type of support needed to promote patient and family healing after such events. We sought to describe the long-term impacts (LTIs) reported by patients and family members who experienced harmful medical events 5 or more years ago. METHODS: We performed a content analysis on 32 interviews originally conducted with 72 patients or family members about their views of the factors contributing to their self-reported harmful event. Interviews selected occurred 5 or more years after the harmful event and were grouped by time since event, 5 to 9 years (22 interviews) or 10 or more years (10 interviews) for analysis. We analyzed these interviews targeting spontaneous references of ongoing impacts experienced by the participants. RESULTS: Participants collectively described the following four LTIs: psychological, social/behavioral, physical, and financial. Most cited psychological impacts with half-reporting ongoing anger and vivid memories. More than half reported ongoing physical impacts and one-third experienced ongoing financial impacts. Long-term social and behavioral impacts such as alterations in lifestyle, self-identity, and healthcare seeking behaviors were the most highly reported. CONCLUSIONS: These patients and families experienced many profound LTIs after their harmful medical event. For some, these impacts evolved into secondary harms ongoing 10 years and more after the event. Our results draw attention to the persistent impacts patients and families may experience long after harmful events and the need for future research to understand and support affected patients and families.

Encouraging Patients to Speak up About Problems in Cancer Care.

OBJECTIVES: Many patients with cancer believe that something has gone wrong in their care but are reluctant to speak up. This pilot study sought to evaluate the impact of an intervention of active outreach to patients undergoing cancer treatment, wherein patients were encouraged to speak up if they had concerns about their care and to describe the types of concerns patients reported. METHODS: Patients receiving cancer care at two sites were randomly assigned to an intervention or control group. Intervention patients received a brochure encouraging them to speak up about any concerns and an outreach telephone call during which the interviewer explicitly asked about concerns. Participants in both groups received baseline and follow-up questionnaires assessing their perceptions of their care and whether anything had "gone wrong" and provided ratings of health care providers' communication and responsiveness. Qualitative content coding was used to categorize patient-reported concerns collected through the baseline and follow-up questionnaires (both groups) and during telephone outreach (intervention patients only). The primary outcome was the number of patients reporting a concern about their care. Communication and responsiveness ratings for intervention and control group patients were compared using t tests. RESULTS: Of the 60 patients in the intervention group, 34 (56.7%) reported at least one problem or concern, compared with 16 (29.1%) of the 55 patients in the control group (P = 0.003). The telephone outreach in particular resulted in more than half of those reached reporting a new concern (55.3%). We detected no impact of the intervention on patients' ratings of communication or support for speaking up. CONCLUSIONS: Patients in this study reported a variety of concerns in response to active outreach, demonstrating that active outreach to patients can provide healthcare teams and systems the opportunity to offer a real-time response to the patient, identify where system improvements are needed, and implement policies, procedures, or programs to prevent recurrences.

Single-Stage Adipofascial Turnover Flap as an Alternate Option for Large Nasal Defects Usually Requiring Two-Stage Forehead Flap.

BACKGROUND: Large nasal defects involving the tip, ala, and/or columella with denuded cartilage have traditionally required a two-stage forehead flap. As many Mohs patients are presenting older with increased medical comorbidities, a single-stage adipofascial turnover flap with a full-thickness skin graft was developed by the senior author as an alternative method. The authors hypothesize that the adipofascial turnover flap would have similar success rates and cost less than the forehead flap. METHODS: A retrospective review of all patients in the senior author's practice who underwent either a forehead flap or adipofascial turnover flap between January of 2016 and February of 2019 was conducted. The two groups were compared regarding success, complications, and cost. RESULTS: There were seven forehead flap patients and 11 patients with adipofascial turnover flaps. Overall complications were three of seven (43 percent) for the forehead flap group and one of 11 (9 percent) for the adipofascial turnover flap group. There was one mortality, one revision for asymmetry, and one with airflow obstruction in the forehead group. The adipofascial turnover flap group had one partial skin graft loss that healed with local wound care only. There were no flap failures in either group, and the cost savings averaged over $22,000 in the adipofascial turnover flap group. CONCLUSIONS: The single-stage adipofascial turnover flap with full-thickness skin grafting is a safe, reliable, and less expensive alternate to the forehead flap. The forehead flap will remain a workhorse in nasal reconstruction, but multiple operations increase cost and may contribute to higher complication rates. The adipofascial turnover flap appears to be an efficacious and reasonable option compared with the forehead flap.

Adenosine monophosphate deaminase 3 null mutation causes reduction of naive T cells in mouse peripheral blood.

Adenosine monophosphate deaminase 3 (Ampd3) encodes the erythrocyte isoform of the adenosine monophosphate (AMP) deaminase gene family. Mutations in this gene have been reported in humans, leading to autosomal-recessive erythrocyte AMP deaminase deficiency. However, the mutation is considered clinically asymptomatic. Using N-ethyl-N-nitrosourea mutagenesis to find mutations that affect peripheral lymphocyte populations, we identified 5 Ampd3 mutations (Ampd3guangdong, Ampd3carson, Ampd3penasco, Ampd3taos, and Ampd3commanche) that strongly correlated with a reduction in naive CD4+ T and naive CD8+ T-cell populations. Causation was confirmed by targeted ablation of Ampd3. Knockout mice had reduced frequencies of CD62LhiCD44lo CD4+ naive and CD8+ naive T cells. Interestingly, these phenotypes were restricted to T cells circulating in peripheral blood and were not seen in T cells from secondary lymphoid organs (lymph nodes and spleen). We found that reduction of naive T cells in the peripheral blood of Ampd3-/- mice was caused by T-cell-extrinsic factor(s), which we hypothesize to be elevated levels of adenosine triphosphate released by Ampd3-deficient erythrocytes. These findings provide an example in which disruption of an erythrocyte-specific protein can affect the physiological status of lymphocytes in peripheral blood.

A Sustainable and Scalable Multidisciplinary Airway Teaching Mission: The Operation Airway 10-Year Experience.

OBJECTIVE: To address whether a multidisciplinary team of pediatric otolaryngologists, anesthesiologists, pediatric intensivists, speech-language pathologists, and nurses can achieve safe and sustainable surgical outcomes in low-resourced settings when conducting a pediatric airway surgical teaching mission that features a program of progressive autonomy. STUDY DESIGN: Consecutive case series with chart review. SETTING: This study reviews 14 consecutive missions from 2010 to 2019 in Ecuador, El Salvador, and the Dominican Republic. METHODS: Demographic data, diagnostic and operative details, and operative outcomes were collected. A country's program met graduation criteria if its multidisciplinary team developed the ability to autonomously manage the preoperative huddle, operating room discussion and setup, operative procedure, and postoperative multidisciplinary pediatric intensive care unit and floor care decision making. This was assessed by direct observation and assessment of surgical outcomes. RESULTS: A total of 135 procedures were performed on 90 patients in Ecuador (n = 24), the Dominican Republic (n = 51), and El Salvador (n = 39). Five patients required transport to the United States to receive quaternary-level care. Thirty-six laryngotracheal reconstructions were completed: 6 single-stage, 12 one-and-a-half-stage, and 18 double-stage cases. We achieved a decannulation rate of 82%. Two programs (Ecuador and the Dominican Republic) met graduation criteria and have become self-sufficient. No mortalities were recorded. CONCLUSION: This is the largest longitudinal description of an airway reconstruction teaching mission in low- and middle-income countries. Airway reconstruction can be safe and effective in low-resourced settings with a thoughtful multidisciplinary team led by local champions.

Delivery of hepato-pancreato-biliary surgery during the COVID-19 pandemic: an European-African Hepato-Pancreato-Biliary Association (E-AHPBA) cross-sectional survey.

BACKGROUND: The extent of the COVID-19 pandemic and the resulting response has varied globally. The European and African Hepato-Pancreato-Biliary Association (E-AHPBA), the premier representative body for practicing HPB surgeons in Europe and Africa, conducted this survey to assess the impact of COVID-19 on HPB surgery. METHODS: An online survey was disseminated to all E-AHPBA members to assess the effects of the pandemic on unit capacity, management of HPB cancers, use of COVID-19 screening and other aspects of service delivery. RESULTS: Overall, 145 (25%) members responded. Most units, particularly in COVID-high countries (>100,000 cases) reported insufficient critical care capacity and reduced HPB operating sessions compared to COVID-low countries. Delayed access to cancer surgery necessitated alternatives including increased neoadjuvant chemotherapy for pancreatic cancer and colorectal liver metastases, and locoregional treatments for hepatocellular carcinoma. Other aspects of service delivery including COVID-19 screening and personal protective equipment varied between units and countries. CONCLUSION: This study demonstrates that the COVID-19 pandemic has had a profound adverse impact on the delivery of HPB cancer care across the continents of Europe and Africa. The findings illustrate the need for safe resumption of cancer surgery in a "new" normal world with screening of patients and staff for COVID-19.

Tissue-specific disruption of Kbtbd2 uncovers adipocyte-intrinsic and -extrinsic features of the teeny lipodystrophy syndrome.

Loss of KBTBD2 in all tissues causes the teeny phenotype, characterized by insulin resistance with late failure of insulin production, severe hyperglycemia/diabetes, lipodystrophy, hepatosteatosis, and growth retardation. KBTBD2 maintains insulin sensitivity in adipocytes by restricting the abundance of p85α. However, the possible physiological contribution or contributions of KBTBD2 have not yet been examined in other tissues. Here we show that mice with an adipocyte-specific knockout of Kbtbd2 accumulate p85α in white and brown adipose tissues, causing insulin resistance, moderate rather than severe hyperglycemia, sustained hyperinsulinemia without late failure of insulin production, and lipodystrophy leading to ectopic lipid accumulation in the liver. Adipocyte-extrinsic insulin resistance was observed in liver and muscle. None of these abnormalities were observed in liver- or muscle-specific Kbtbd2 knockout mice. Mice with Kbtbd2 knockout in adipocytes, liver, and muscle all showed normal growth, suggesting that KBTBD2 may be necessary to ensure IGF1 signaling in other tissues, notably bone. While much of the teeny phenotype results from loss of KBTBD2 in adipocytes, some features are adipocyte-extrinsic.

Essential requirement for nicastrin in marginal zone and B-1 B cell development.

γ-secretase is an intramembrane protease complex that catalyzes the proteolytic cleavage of amyloid precursor protein and Notch. Impaired γ-secretase function is associated with the development of Alzheimer's disease and familial acne inversa in humans. In a forward genetic screen of mice with N-ethyl-N-nitrosourea-induced mutations for defects in adaptive immunity, we identified animals within a single pedigree exhibiting both hypopigmentation of the fur and diminished T cell-independent (TI) antibody responses. The causative mutation was in Ncstn, an essential gene encoding the protein nicastrin (NCSTN), a member of the γ-secretase complex that functions to recruit substrates for proteolysis. The missense mutation severely limits the glycosylation of NCSTN to its mature form and impairs the integrity of the γ-secretase complex as well as its catalytic activity toward its substrate Notch, a critical regulator of B cell and T cell development. Strikingly, however, this missense mutation affects B cell development but not thymocyte or T cell development. The Ncstn allele uncovered in these studies reveals an essential requirement for NCSTN during the type 2 transitional-marginal zone precursor stage and peritoneal B-1 B cell development, the TI antibody response, fur pigmentation, and intestinal homeostasis in mice.

Communicating with patients about diagnostic errors in breast cancer care: Providers' attitudes, experiences, and advice.

OBJECTIVE: To gain understanding of breast cancer care providers' attitudes regarding communicating with patients about diagnostic errors, to inform interventions to improve patient- provider discussions. METHODS: Focus groups were held in three U.S. states involving 41 breast cancer care providers from a variety of specialties. Discussions focused on providers' experiences with potential errors in breast cancer diagnosis, communication with patients following three hypothetical diagnostic vignettes, and suggestions for how and why diagnostic errors in breast cancer care should be communicated. Transcripts were qualitatively analyzed. RESULTS: Providers were more willing to inform breast cancer patients of a diagnostic error when they felt it would be helpful, when they felt responsible for the error, when they were less concerned about litigation, and when the patient asked directly. CONCLUSIONS: Breast cancer care providers experience several challenges when considering whether to inform a patient about diagnostic errors. A better understanding of patients' preferences for open communication, combined with customized tools and training, could increase clinicians' comfort with these difficult discussions. PRACTICE IMPLICATIONS: Providers gave suggestions to facilitate discussions about diagnostic errors when these events occur, including themes of education, honesty, and optimism.