Scientific advancements have led to more people living longer with metastatic breast cancer (MBC). Antibody-drug conjugates (ADCs) offer a promising treatment option, but currently approved ADCs are associated with significant side effects that can impact quality of life. Dose reductions may help mitigate these effects, yet little is known about real-world, patient-reported experiences with ADC dosing. We surveyed 170 individuals with MBC who had received ADC treatment to assess initial dosing, dose modifications, and barriers to supportive care. Most respondents (94.1%) began treatment with the recommended dosing frequency and 82.9% with the recommended dose. However, 35.3% reported dose reductions, primarily due to experienced or anticipated side effects. Open-ended responses underscored the burden of side effects: “If not for low dose, I don’t think I could go on.” Most participants (81.0%) reported oncologist-led efforts to manage side effects, and 73.0% used medications for symptom control. Financial barriers were common, with 43.5% reporting difficulty accessing supportive care. These findings highlight the need for patient-centered dosing strategies and improved access to supportive care.

Introduction:The Young Children's Participation in Environment Measure (YC-PEM) is an evidence-based and promising electronic patient-reported outcome (e-PRO) option to improve early intervention (EI) service quality, such as when designing the EI service plan. Aim:Establish the preliminary effectiveness of implementing the YC-PEM e-PRO and program-specific shared decision support tool option for EI service quality when designing a service plan. Methods:For this 2-arm pilot pragmatic trial with cluster randomization at the provider level, 76 caregivers enrolled and 57 caregivers (n = 29 intervention group; n = 28 control group) completed pre- and post-intervention measures. Intervention group caregivers completed the YC-PEM e-PRO and program-specific shared decision support tool and were compared to usual care on EI service quality indicators: (1) caregiver perceptions of family-centeredness, (2) caregiver activation for shared decision-making, (3) caregiver engagement in service design and implementation; and (4) service plan quality. Results:No significant group differences at baseline were noted. Pre-post EI service quality revealed no significant differences in the adjusted model (P > .05). However, intervention group families had higher rates participation-focused service plans (69.2%) versus controls (51.4%), most of which met state-level criteria for quality (84%). Conclusion:For EI service quality indicators, this intervention option demonstrated comparable performance to usual care. This finding suggests the intervention promoted high quality, participation-focused service planning despite no overall differences in EI service quality, warranting further testing of implementation factors and effectiveness in various service contexts.Trial Registration Number: NCT04562038.

Introduction Limited literature exists describing the processes associated with developing and refining data collection tools. Thus, there is little opportunity to share lessons learned and strategies to overcome challenges. In this manuscript, we share our process of developing and iterative refining a data collection tool called SSPOT (Sociotechnical Systems Prospective Observational Tool) with the intended use of conducting observations in clinical settings. Methods Using SEIPS 2.0 as a guide, we developed and iteratively refined a digital tool (within REDCap) that facilitates capture of observational data in (near) real time across 4 phases: Prototype Development and Refinement, Nonclinical Pilot Testing, Clinical Pilot Testing, and Inter-Observer Consistency. Results The resultant tool supports manual documentation of observational data associated with activities, personnel, and tools/technologies. Development took 99 h, including 71 h of observation and 28 h of debriefing over 9 weeks, of which approximately 4 h of pilot testing were in a non-clinical setting. The coffee shop served as a successful alternative sociotechnical system for pilot testing.Once development was completed, the tool was used in an adult and a pediatric ED for three observational studies that cumulatively collected data for 399.08 h. Discussion By sharing the iterative development process, we aim to inform future de novo observational data collection tool development efforts. We recommend that research teams: 1) gather a team with multiple perspectives including human factors 2) plan and budget accordingly (including time) for data collection tool development and refinement, 3) consider leveraging creative and easily-accessible non-clinical settings for testing prior to piloting in the clinical setting.

e12738 Background: Patient decision making is understudied and seldom focused on those diagnosed with cancer. This NCI-supported knowledge acquisition study sought to characterize patient knowledge of those newly diagnosed with breast cancer and examine how it informs decision making. Methods: We recruited participants in the US, > 18 years, within three months of a breast cancer diagnosis to participate in 1-hour semi-structured interviews on Zoom with compensation. An interview guide was developed to elicit patient knowledge state, as well as acquisition and sources regarding diagnosis and next steps. Interviews were audio-recorded, transcribed, and analyzed using Braun and Clarke’s (2006) thematic analysis of qualitative data. Results: We interviewed 26 female participants with a mean age of 51. Approximately 54% (n = 14), 31% (n = 8), and 4% (n = 1) were White, Black, and Asian, respectively and 4% (n = 1) were Hispanic. Below, we highlight a selection of themes. Diagnosis and next steps: Patients reported inconsistent experiences of receiving their diagnosis. Eighteen patients received a report via MyChart with follow-up communication from a provider (n = 5) on a timeline of hours to days, or not at all. Only some patients reported receipt of an explanation from their provider. Patients often sought clarification through external resources (e.g. Google, Reddit, TikTok, Instagram, Facebook patient communities, survivors in their networks). Four participants used AI to help understand their pathology reports, medical terminology, treatment options, and next steps. Roles of clinical care team: Some patients demonstrated incomplete understanding of the structure of their care team. Half (n = 14) used the term “doctor” to refer to either the primary care provider or oncologist (without clarity to what role). Only a few patients mentioned having a patient navigator and, when prompted, some patients reported that they either did not have one or that they did not know. Second opinion: Some patients did not talk about seeking a second opinion (suggesting they did not), while others reported feeling empowered to do so (n = 9), influenced by their social network and embodied knowledge, yet another reported discomfort associated with doing so. Conclusions: During the diagnostic phase, patients report lack of support in acquiring credible foundational knowledge. Findings suggest that patient-driven knowledge acquisition is an active and iterative process that begins at diagnosis, not at treatment selection. Specifically, patients continuously assess what they know, do not know, and how to fill the gaps. Highlighted by the variability in reported patient experiences in both receiving and seeking information, many report inconsistent support. Implications include that without effective information transmission, patients may not have decision making agency.

e13085 Background: Metastatic breast cancer (MBC) involves complex treatment plans, as patients and their oncologists must balance extending life with maintaining quality of life, within a landscape of rapidly increasing therapeutic options. Shared Decision-making (SDM), a collaborative approach between clinician and patient, underscores the importance of patient engagement in their treatment decisions. This patient-led study examined the relationship between seeing a breast specialist and perceptions of shared decision-making for people with MBC. Methods: We collected data using a self-administered survey developed by the Patient-Centered Dosing Initiative, a patient-led nonprofit working to bring real-life experience into cancer treatment decisions. Eligible participants were aged ≥18 years, US residents, with a self-reported history of MBC. Participants were asked whether their primary oncologist treated exclusively breast cancer patients (yes/no/I don’t know). They also rated their level of agreement on a 6-point (0 to 5) scale using the validated 9-item SDM-Q-9 instrument. We calculated the median (Med) and standard deviation (SD) of the summed SDM score (Min:0, Max: 45) and of individual SDM-Q-9 items (Min: 0, Max: 5), where higher scores indicated having a greater sense of SDM. We used Mann-Whitney U tests to compare medians between respondents who saw a breast specialist and those who did not. P values less than 0.05 were considered statistically significant. Results: There were 501 respondents with MBC with complete survey data. Participants had a mean age of 55 and 62.9% (n = 315) reported seeing a breast specialist. The overall median summed SDM-Q-9 was 40 (SD:15.2) and was statistically different (p = 0.043) between respondents who saw a breast specialist (Med: 42, SD: 15.7) and those who did not (Med: 37, SD: 14.2). For the specific SDM item “My doctor and I selected a treatment option together,” respondents who saw a breast specialist had significantly higher median SDM scores (Med: 5.0, SD: 1.6) than those who did not (Med: 4.0, SD: 1.5), (p = 0.011). For the SDM item “My doctor precisely explained the advantages and disadvantages of treatment options,” respondents who saw a breast specialist had significantly higher median SDM scores (Med: 5.0, SD: 1.4) than those who did not (Med: 4.0, SD: 1.4), (p = 0.008). Conclusions: Patients with MBC reported high levels of shared decision-making overall; however, patients treated by breast specialists reported significantly greater overall shared decision-making. The differences across several subdomains indicate that patients seeing breast specialists may be more involved in treatment selection and communication about treatment trade-offs. These differences identify potential system-level targets across different types of oncology practices to improve patient-centered, preference-concordant care in MBC.

Background: HER2+ targeted treatment for metastatic breast cancer (MBC) is one of the first successes of targeted therapy for advanced cancer, with some patients having years of disease control without any evidence of active disease progression. This has led to unanswered questions of how long HER2 targeted therapies should be continued. We aimed to characterize patient experience with anti-HER2 drugs, particularly in those with sustained disease stability. Methods: We developed a questionnaire comprised of closed- and open-ended questions to elicit experiences of patients diagnosed with HER2+ MBC. Particular attention was directed at whether patients considered stopping or pausing HER2-targeting treatment after achieving no evidence of disease (NED) and the associated decision making process. We administered the questionnaire online via outreach to MBC patients through social media and nonprofit digital newsletters. Results: A total of 124 people in the United States responded, 82 (66%) were diagnosed with de novo MBC and 42 (34%) were originally diagnosed with early-stage. Following initial use of a taxane +/- carboplatin + trastuzumab +/- pertuzumab, continued trastuzumab +/- pertuzumab was the most common treatment regimen among the surveyed. At least 95 (76%) had experienced =/>1 year of progression-free disease after starting treatment and 65 (52%) were NED at time of response. Eighty-five (68%) had reached NED after a median time on treatment of 6 months; among these patients, 45% stated they had either discussed or thought about discussing with their oncologist the possibility of stopping HER2-targeting treatment. Level of education was shown to be significantly associated with considering HER2 treatment termination, with more years post high school education corresponding with greater likelihood of having that discussion. In 32% (12/38) of cases, the discussion was initiated by the oncologist. Of these, 7 patients (18%) decided to terminate treatment. Among respondents who had considered stopping treatment, the most common reason given was side effects, followed by emotional toll of continuous treatment. Patients who achieved NED status reported that the lack of evidence for safety was the chief reason to continue treatment despite questioning its need. Many patients reported quality of life (QoL) challenges, including debilitating side effects (e.g. severe itch) and impact to their financial wellbeing. Patients’ descriptions of their decision making processes ranged from “Since it's working we won't switch” to “…it was a matter of not killing myself over enduring the pain & itch” with most reporting that they made the decision together with their oncologist, although some reported that just the oncologist (11%) or just the patient (13%) made the decision. Conclusion: Nearly half of surveyed patients who achieved NED considered stopping HER2-targeting treatment. However, the range of responses regarding the decision making process highlights a problem space in need of research attention to better characterize barriers and facilitators associated with decision and patient-oncologist communication. We found that more educated patients were more likely to question continued HER2 treatment and that their clinicians were more likely to engage in these complex conversations. These findings indicate the potential for a treatment gap between subsets of patients that is not based on treatment efficacy nor QoL. There is a need for clinicians to be prepared for complex conversations with a high level of uncertainty and to conduct them in a way that is comprehendible to all patients to support shared decision making. Conversations about potential risks to staying on treatment or going off treatment are deserved by all patients, even if we have to wait for prospective studies, such as the ongoing Stop-HER2 (NCT05721248) and Free-HER (NCT05959291), to provide more definitive levels of these risks for the MBC population. Citation Format: Martha Carlson, Guy R. Adami, Maryam B. Lustberg, Tahniat Nadeem, Elizabeth Lerner Papautsky. Characterizing Patient Experience and Decision Making Associated with Considering Stopping or Pausing HER2-targeted Treatment for MBC Population Using a Questionnaire [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-05-18.

OBJECTIVE:To examine patient-provider nutrition conversations at initial prenatal visits. DESIGN:Convergent mixed methods observational study. SETTING:Two large metropolitan clinics in the midwestern United States. PARTICIPANTS:Sixteen providers and 20 racially diverse pregnant women. METHODS:Guided by the Systems Engineering Initiative for Patient Safety (SEIPS) 2.0 model, we observed and audio-recorded initial prenatal visits with obstetric providers. Patients completed post-visit surveys and interviews, and providers completed post-visit interviews. Finally, we sent a practice-wide electronic survey to all providers. We completed quantitative data analysis for descriptive statistics of observation and survey results. We completed qualitative thematic analysis of visit and interview transcripts and combined and categorized results into components of the SEIPS 2.0 model. RESULTS:We identified multiple dynamic and interacting factors relevant to the work system and processes in the SEIPS 2.0 model in patient-provider conversations about nutrition. Although nutrition was covered in all visits, most conversations were provider-centered and covered basic, general recommendations related to a limited number of topics. Few individualized collaborative discussions that addressed contextual factors occurred. CONCLUSION:Finding ways to incorporate and address contextual factors into patient-centered conversations about nutrition is vital to optimize the dietary habits of women, especially those from vulnerable populations. To do this, multidisciplinary teams that include nurse practitioners, nurses, obstetricians, and registered dietitians who can address the multiple social determinants of health that affect dietary choices are needed.

Abstract Introduction A notable shift has occurred in medical relationships, placing greater emphasis on the role of patients within the healthcare system. A nascent body of literature in the US captures the experiences of patients following a diagnosis, but this is lacking in Nigeria. We used Systems Engineering Initiative for Patient Safety (SEIPS 2.0) as a theoretical framework from the discipline of human factors that serves as a guide for characterizing complex sociotechnical systems comprised of factors, work processes, and outcomes - with the patient and clinicians at the center. We specifically focused on the patient work network, which refers to individuals and communities that play role in supporting patient work. The objective of this study was to elicit the experiences of Nigerian breast cancer patients and healthcare providers by qualitative interviews and characterize productive and counterproductive activities of the patient work network. Methods The study was approved by the IRB. We used snowball sampling and social media to recruit Nigerian breast cancer patients and health care providers with experience treating breast cancer. One researcher conducted interviews that lasted 30–60 min using teleconferencing technology and an interview guide developed for this study. Questions for both patients and healthcare providers covered topics such as patient response to diagnosis, barriers and facilitators to care including people and communities within the patient’s network. We calculated descriptive statistics for demographics. Using thematic analysis, we carried out the analysis in the following stages: data review, category coding and data extraction, and synthesis and integration of findings. Results We interviewed 18 female patients (29-67 yrs old) and 6 healthcare providers (31-42 yrs old; 3 males). Twelve patients received treatment in urban areas and 6 in rural. Four patients had a bachelor's degree. Healthcare providers included primary, specialty, palliative, treatment, diagnostic care. We highlight a subset of the dataset with focus on productive versus unproductive work conducted by family and by religious community, with unproductive defined as potentially having negative impact on the patient and their experience (Table 1). Providers stated that patients who receive family support exhibit better health outcomes compared to those who do not. Providers shared that religious community can perpetuate patient denial in their diagnosis. Both patients and providers discussed an inclination towards seeking traditional care. Despite recognizing the challenges and pressures faced by patients, providers lacked in-depth understanding of the specific experiences patients encountered. Conclusion Our findings highlight the role of family and religious community in conducting activities that are both productive and unproductive facilitating productive activities and its influence on the decision-making process of patients. Alternatively, both family and religious community engage in activities counterproductive to the patient and their illness. Findings emphasize the importance of comprehensive support systems, education, and targeted interventions to improve the experiences and outcomes of Nigerian breast cancer patients. Effective strategies should address cultural beliefs, empower patients to make informed decisions, and enhance provider knowledge regarding the unique challenges faced by patients within the identified barriers. Table. Productive versus unproductive work conducted by family and by religious community Citation Format: Blessing Nwachukwu, Elizabeth Papautsky. Capturing Experiences: Navigating Breast Cancer Treatment of Nigerian Patients and Healthcare Providers Using Qualitative Interviews [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-10-09.

INTRODUCTION:Dietary intake during pregnancy impacts short- and long-term maternal and fetal health outcomes. Dietary habits are highly individualized and influenced by contextual factors and social determinants of health within each person's lived environment. Midwives and other health care providers are well positioned to facilitate nutrition conversations and interventions with patients related to recommendations and modifications before and during pregnancy. This scoping review synthesizes the literature on perinatal care providers' attitudes and practices related to antenatal nutrition counseling. METHODS:An electronic database literature search was conducted in March 2023 using the following inclusion criteria: English language, published between 1990 and 2023, completed in high-income countries, and evaluated provider practices related to educating pregnancy patients on nutrition. Exclusion criteria included comparison or interventional studies as well as those focused on patient perspectives, specialty diets, comorbidities, or pregnancy complications. Thematic analysis was completed to identify common themes and subthemes across studies related to perinatal care providers' perspectives of pregnancy nutrition. RESULTS:Thirty-six articles were included in the final review. Although providers acknowledged the importance of nutrition for pregnancy outcomes, few reported being able to cover the topic in-depth during antenatal visits. Counseling was usually generalized, limited in scope, and lacked consideration of patient-specific contextual factors such as dietary restrictions, preferences, or access to resources needed to follow recommendations. Provider barriers to comprehensive nutrition counseling included lack of training and time during clinic visits and limited availability of guidelines. DISCUSSION:Multiple gaps in current pregnancy nutrition counseling practices exist. Despite nutrition being viewed by perinatal care providers as an important part of pregnancy, multiple barriers lead to it being overlooked during patient-provider interactions. Contextual factors for both providers and patients contribute to failure of current interventions to consistently and significantly impact dietary habits of pregnant people.

This paper underscores the need for increased human factors research in cancer care and the involvement of human factors professionals in this field. While human factors principles have been widely applied in aviation, driving, and some aspects of healthcare to enhance safety and usability, they remain underutilized in cancer care. The authors employed HTML parsing to extract titles and abstracts from five journals and two conference proceedings, identifying cancer-related articles through predefined keywords from 1958 to 2022. Among the total of 25,033 articles reviewed from these sources, only 28 pertained to cancer, with colorectal, breast, and prostate cancer being the most frequently discussed. Notably, 67% of the articles were found in the Human Factors National Conference Proceedings. The paper advocates for the hiring of human factors professionals in oncology departments within hospitals and emphasizes the need for special issues and funding to advance this vital research area.

This paper investigates the creation of a multi-disciplinary team and their journey to integrate human factors science into academic medicine. This work explores the many areas in which implementation of human factors thinking has changed their world as physicians – through direct clinical care, medical education, physician research, and leadership/operational roles.

The prevalence of artificial intelligence (AI) is rapidly growing across industries including in health care. AI has the potential to improve patient safety (e.g., diagnostic error) and reduce clinician workload (e.g., documentation burden) and healthcare costs. Yet, many questions remain about how clinicians will interact with and use AI to support their work and how these technologies will impact clinician workflow, decision-making, and teamwork. It is also uncertain how patients will interact with AI, with a recent report suggesting 60 percent of US adults are uncomfortable with their health care providers using AI. In this panel, we will discuss AI applications across differing health care contexts and describe how AI influences clinician (and patient) workflows. We will outline considerations for the design and implementation of AI-based technologies in health care and needed areas of future research.

This paper investigates the relationship between knowledge of baseline heart rate and shock recognition in pediatric patients. Through surveying attending physicians and advanced practice providers using a prospective survey tool, we demonstrate that providers are more likely to accurately identify shock when there is knowledge of the patient’s baseline heart rate. These preliminary findings have the potential to inform changes to documentation and the electronic health record (EHR) to make this information more accessible, while also informing future studies aimed at improving clinical outcomes for these high-risk patients.

Background: The contributions of cognitive and behavioral work of patients' family members in intensive care units remain largely unrecognized. Objective: The objective of this study was to develop a framework of outwardly observable family work, with specific focus on describing the physical space. Methods: We conducted approximately 50 hrs of naturalistic observations of family activities on a medical intensive care unit (MICU) at a large, Midwestern teaching hospital. Results: We created a framework of activities that include requesting, receiving, or delivering either information or action, along with examples. Further, we identified clinician and staff roles with whom families interact and characterized the physical spaces in which interactions take place. Conclusions: Knowledge contribution is a proposed framework of family activities in the MICU. It has the potential to guide and be further described by future research and to inform development of human-centered family-facing interventions to support cognitive and behavioral cognitive and behavioral work.

213 Background: Community-based patient navigation has emerged as a highly effective strategy to increase cancer screening and early diagnosis, particularly for underserved populations. This navigation typically ends at diagnosis, when patients transition to clinical care. However, clinical navigation offers limited assistance to connect survivors with a broad range of community resources and support services. Community-based survivorship navigators have the potential to bridge this gap. We implemented a virtual learning collaborative (VLC) to build community capacity to deliver breast cancer survivorship navigation. Our research assesses the impact of the VLC on participants' behaviors, self-efficacy, and barriers to navigation. Methods: We conducted an analysis of data from the Breast Cancer Survivorship Patient Navigator Virtual Learning Collaborative (VLC), a 14-week practice-based training for community health workers and patient navigators to address the needs of breast cancer survivors. Weekly 60-minute virtual learning sessions included a brief didactic, followed by participants’ presentation of de-identified client cases. A 27-item pre-post survey was used to assess changes in behaviors, self-efficacy, and barriers to navigation. Results: A total of 40 participants completed both the pre- and post-surveys. Participants were predominantly female (98%), White (55%) or Black (30%), and non-Hispanic (68%). The majority were affiliated with community-based organizations (50%), as well as health departments (19%), and hospitals/cancer centers (19%) serving urban (50%) and suburban (33%) communities. Survey results indicate an average increase of 24% in self-efficacy, with the greatest increase in ability to serve as a consultant to others on cancer survivorship (38%), link survivors to appropriate resources and services (32%), explain how clinical trials work (32%), and work with survivors to address their needs (32%). Reductions in barriers to navigation included limited knowledge of cancer and cancer treatment (33%) and awareness of survivorship resources and services (34%). We found no change in behaviors or other barriers to navigation. Conclusions: The results of this study indicate the effectiveness of the VLC to build community-based capacity to deliver breast cancer survivorship navigation through increased navigator self-efficacy. No changes in behaviors suggests that navigators provide survivorship support whether or not they have training, and points to a key opportunity to increase their knowledge of evidence-based information and resources. Results of this research provide evidence to support recognition of the critical role of community navigators and reimbursement to ensure high quality, consistent community-based care for cancer survivors.

Objective The aim of the study is to identify and prioritize early intervention (EI) stakeholders' perspectives of supports and barriers to implementing the Young Children's Participation and Environment Measure (YC-PEM), an electronic patient-reported outcome (e-PRO) tool, for scaling its implementation across multiple local and state EI programs.Methods An explanatory sequential (quan > QUAL) mixed-methods study was conducted with EI families ( n = 6), service coordinators ( n = 9), and program leadership ( n = 7). Semi-structured interviews and focus groups were used to share select quantitative pragmatic trial results (e.g., percentages for perceived helpfulness of implementation strategies) and elicit stakeholder perspectives to contextualize these results. Three study staff deductively coded transcripts to constructs in the Consolidated Framework for Implementation Research (CFIR). Data within CFIR constructs were inductively analyzed to generate themes that were rated by national early childhood advisors for their relevance to longer term implementation.Results All three stakeholder groups (i.e., families, service coordinators, program leadership) identified thematic supports and barriers across multiple constructs within each of four CFIR domains: (1) Six themes for "intervention characteristics, " (2) Six themes for "process, " (3) three themes for "inner setting, " and (4) four themes for "outer setting. " For example, all stakeholder groups described the value of the YC-PEM e-PRO in forging connections and eliciting meaningful information about family priorities for efficient service plan development ( "intervention characteristics "). Stakeholders prioritized reaching families with diverse linguistic preferences and user navigation needs, further tailoring its interface with automated data capture and exchange processes ( "process "); and fostering a positive implementation climate ( "inner setting "). Service coordinators and program leadership further articulated the value of YC-PEM e-PRO results for improving EI access ( "outer setting ").Conclusion Results demonstrate the YC-PEM e-PRO is an evidence-based intervention that is viable for implementation. Optimizations to its interface are needed before undertaking hybrid type-2 and 3 multisite trials to test these implementation strategies across state and local EI programs with electronic data capture capabilities and diverse levels of organizational readiness and resources for implementation.

Although the uptake of trastuzumab biosimilars to treat HER2-positive breast cancer is growing, knowledge gaps remain for both, patients and clinicians. In a mixed-methods study, inconsistencies in terminology used to describe trastuzumab biosimilars. We analyzed open-ended questions from surveys (n = 143 breast cancer patients, n = 33 medical oncologists) and interviews (n = 8 patients, n = 4 oncologist, nurse, pharmacists) indentifying terminology as an a priori (top-down) category for qualitative thematic analysis. We specifically looked for examples of inconsistent or incorrect use of terminology in the interviews. Findings suggest that 1) terminology used to refer to trastuzumab biosimilars is variable across patients and some is not representative of the formal definition (e.g. generic, generic-like, interchangeable, Herceptin, generic Herceptin (as per how their oncologist refers to biosimilars) and 2) clinicians discussed the challenges of talking about biosimilars in a manner that is both understandable to patients and accurate. Specifically, one pharmacist highlighted concerns around this complexity and suggested that it should be part of clinician education to use the correct terminology, rather than using the term generic. A medical oncologist said that “Explaining biosimilars to a patient can be challenging” as part of their survey response. Lack of consistent terminology for trastuzumab biosimilars is a potential barrier to effective patient-clinician communication on this topic and may perpetuate lack of comprehension on the part of patients. Further, the intentional use (to make information more digestible to patients) of incorrect terminology by clinicians has the potential to negatively impact the patient-clinician relationship in cases where patients identify conflicting information on their own. The adoption of terminology that is consistent across clinicians and patient-facing resources on the introduction and description of trastuzumab biosimilars, may serve to facilitate common grounding among all roles. Citation Format: Elizabeth Papautsky, Devika Salunke, Hannah Montague, Martha Carlson, Sheila Johnson, Deanna Attai, Maryam Lustberg. Using Mixed Methods to Examine Clinician and Patient Use of Terminology to Describe Trastuzumab Biosimilars [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-09-05.