Background:Health-related social needs (HRSN) significantly influence health outcomes, yet healthcare organizations face persistent challenges tracking referrals to community-based organizations and interpreting referral outcomes across fragmented clinical and social care systems. Prior studies report low referral fulfillment rates, but much of this evidence derives from single organizations, manual data collection, or incentivized documentation workflows, limiting insight into how information infrastructure shapes what is observable at scale. Objective:This study aimed to evaluate how HRSN referral initiation, documented outcomes, and time-to-fulfillment are captured when electronic health record (EHR) data and closed-loop HRSN platform data are integrated through a statewide health information exchange, and to identify informatics strengths and limitations affecting cross-system observability of referral processes. Methods:We conducted a retrospective observational study of 1,628 adult patients from a federally qualified health center and three health systems. Linked EHR and HRSN platform data were used to examine referral initiation, documented fulfillment, and time to fulfillment across resource types. Results:Patients received an average of two referrals, with approximately 80% addressing basic needs. Fewer than 3% were documented as fulfilled, reflecting constrained documentation workflows rather than confirmed absence of service delivery. Short-term needs were more likely to transition to documented outcome states and had shorter documented time-to-fulfillment, whereas long-term needs-particularly housing-exhibited wide variability and documentation patterns consistent with workflow-driven closure behavior. Conclusion:Instead of examining referral fulfillment as a performance metric, the findings suggest how socio-technical infrastructure, workflow design, and documentation incentives affect what becomes observable in secondary use of HRSN data.

BACKGROUND:There is a critical gap in understanding the symptom experience and health outcomes of older adults with and without Alzheimer's Disease and related dementias (ADRD) and polypharmacy (PPY). The primary aim of the study was to compare the number of symptoms experienced over time in older adults with and without ADRD by polypharmacy status. The secondary aim was to examine the trajectory of physical function and health outcomes over time in each group. METHODS:This study utilized longitudinal data from the National Health and Aging Trends Study, a nationally representative sample of Medicare beneficiaries from 2016-2019. The sample was separated into four groups (N = 2,052): neither ADRD or PPY (n = 1,048), PPY only (n = 761), ADRD only (n = 116), and both ADRD and PPY(n = 127). RESULTS:The overall sample was predominately female (57.9%), White (70.9%), aged 84 or younger (75%), married (46%), and had some college or a college degree (50%). Participants with both ADRD and PPY experienced more symptoms on average, had higher odds of falls, hospitalizations, and mortality than all other groups. Older adults with both ADRD and PPY had lower physical function, needed more assistance with activities of daily living and higher assistive device utilization compared to the other three groups. CONCLUSIONS:Findings indicate that older adults with both ADRD and PPY experience more symptoms, negative health outcomes and physical function decline that can negatively impact their quality of life. Further research is needed to identify strategies for reducing PPY in people with ADRD.

Moving in synchrony with others is associated with heightened social engagement and cooperation between individuals. Creative arts-based approaches such as dance/movement therapy (DMT) incorporate nonverbal techniques to develop interpersonal synchrony and group cohesion, and to enhance kinesthetic empathy. While DMT commonly uses Laban Movement Analysis (LMA), an analytical assessment system to observe and interpret movement, it is subject to personal bias and observer fatigue. Therefore, our goal was to explore the utility of the accelerometer to objectively measure rhythmic synchrony (RS) and spatial synchrony (SS) with 14 middle school students during 10 weekly group DMT sessions and to examine changes in mean scores for RS and SS over three time points. A wrist-worn accelerometer and Laban Movement Analysis (LMA), were used to measure RS and SS between individuals in each group. Biometric and observational data were compared to observe trends between both data sets. Participants’ subjective experiences of wearing the device during movement were also investigated. Although no statistical significance was found in IS scores across groups, in comparing the two data sets, overall biometric scores of RS increased marginally between the three time points, and overall observational scores notably increased between T1 and T2 and decreased between T2 and T3. Group 2 demonstrated similar upward trends in both data sets. This study is the first to investigate the useability of the accelerometer to measure interpersonal synchrony in DMT. Although the findings are encouraging, further investigation is needed to provide definitive information on the usefulness of the accelerometer in this context. Limitations and suggestions for future research are included.

Housing disrepair (leaking roofs/walls, broken plumbing/heating) is increasingly common among older adults who often struggle to repair and maintain their homes. Unknown is whether housing disrepair is associated with rates of functional disability and if this association varies for higher and lower income households. Drawing on cross-sectional data (N = 17,610 households with older adults ≥65 years) from the U.S. Census Bureau’s American Housing Survey national survey (2023), we characterized housing disrepair and its associations with functional disability. Housing disrepair was measured as occupant report of at least one of 40 problems across 8 categories (electricity, heating, inside structural, bathroom, kitchen, outside structural, water, sewer). Overall, 36.2% of older adult households reported disrepair; 38.5% among low-income and 34.9% among moderate/high-income households. Functional disability (measured as older adult occupant with difficulty bathing or dressing, doing errands, concentrating or remembering, or climbing or walking stairs) was more prevalent among households with disrepair than without (36.3% vs 24.8%). In a fully adjusted logistic regression model, the odds of an older adult occupant having a functional disability was 1.81 (95% CI 1.65, 1.98) times as high in households with vs without disrepair. In additional adjusted models stratified by income, the odds ratios for the association between disrepair and functional disability were similar in low-income (OR 1.87; 95% CI 1.65, 2.12) and moderate/high-income households (OR 1.77; 95% CI 1.55, 2.02). Further research is needed to establish a causal relationship between housing disrepair, income, and disability and identify causes and interventions to decrease disrepair among older adult households.

Contingency management (CM) is an effective intervention that provides financial incentives as positive reinforcement for reducing opioid or stimulant use. However, it has not been tested in populations of women who inject drugs (WWID) engaging in polysubstance use. We aimed to compare the feasibility of two CM protocols designed to encourage illicit stimulant and opioid abstinence among WWID participating in an ongoing HIV prevention trial. Participants completed a 3-month CM period during which they submitted thrice weekly urine toxicology screenings (UTOX). In the ‘abstinence from stimulants and opioids’ protocol, participants received a 5 USD incentive when metabolites of stimulants and opioids were not detected in urine. In the ‘partial-abstinence protocol’, they received a5 USD incentive when metabolites of stimulants or opioids were not detected, thus doubling the potential incentive obtained each visit. Women also received scaling bonuses after three consecutive negative UTOX (5-15 USD). We used descriptive statistics to summarize the total number of (1) UTOXs completed and (2) bonuses distributed. Rates of engagement per person per month were calculated (i.e., total number of completed UTOX/3 months*24 participants). Rates of engagement were compared by CM protocol period. Participants were primarily White women (67

e21566 Background: Approximately 2500 new uveal melanoma (UM) cases (5.2 cases per million population) are diagnosed yearly in the United States. We previously identified three unique geospatial accumulations of UM in North Carolina, Alabama, and New York based on our clinical experience. Such unexpected findings prompted us to conduct a more systematic evaluation of geospatial accumulations of UM patients at our institution. Methods: Through the electronic medical record system, we identified patients seen at our institution with a diagnosis of UM. Identified living patients and family of deceased patients were either sent an e-mail or paper letter with an internet link to a survey. The survey asked for the patient’s name, date of birth, sex, date of primary UM diagnosis, address at time of UM diagnosis and number of years at that address, and all previous addresses and dates of residence prior to the UM diagnosis. Using these addresses, ArcGIS and R software was used to analyze the geospatial distribution of our UM patients. The data was supplemented with 2020 American Community Survey census estimates at the state, county, and census tract level to estimate population-based rates of UM. Results: We identified 2718 UM patients in our clinical database, and a total of 726 participants completed the survey with a total of 2939 US addresses. The majority of addresses were precise to the street address level (77.9%). At the time of UM diagnosis, patients had lived at their current address for a median of 16 years. Pennsylvania and the neighboring states expectedly made up the majority (63.6%) of our patients, but about 1/3 of our patients resided in other states at the time of their UM diagnosis (total of 42 different states). Several counties presented elevated rates of UM with ≥5 case per 100,000 persons. We observed a group of counties in central Pennsylvania, at the border of Pennsylvania and New York, and in upper New York by the Finger Lakes with notably elevated rates of UM, which was consistent with our clinical observations at our institution. Several neighboring counties in Kentucky and Virginia also presented elevated rates. Conclusions: Through this pilot project, we have demonstrated that it is possible to collect lifetime residency information from UM patients in order to map their geospatial distribution in the US. Furthermore, although institutional bias toward referring physicians should be considered, our geospatial analysis identified accumulations of UM in areas similar to our clinical concerns. The results of our study warrant further investigations into environmental influences on UM development. Our future goal is to extend our approach through national and international collaborations to increase the number of participants in the analysis and to minimize institutional bias.

Background:Digital technologies allow users to engage in health-related behaviors associated with positive outcomes. We aimed to identify classes of US adults with distinct digital technologies access and health use patterns and characterize class composition. Data came from Health Information National Trends Survey Wave 5 Cycles 1-4, a nationally representative cross-sectional survey of US adults (N=13,993). We used latent class analysis to identify digital technologies access and health use patterns based on 32 ternary variables of behaviors and access to requisite technologies and platforms, including the internet, internet-enabled devices, health monitors, and electronic health records (EHRs). We ran a multinomial logistic regression to identify sociodemographic and health correlates of class membership (n=10,734). Results:Ten classes captured patterns of digital technology access and health use among US adults. This included a digitally isolated, a mobile-dependent, and a super user class, which made up 8.9%, 7.8%, and 13.6% of US adults, respectively, and captured access patterns from only basic cellphones and health monitors to near complete access to web-, mobile-, and EHR-based platforms. Half of US adults belonged to classes that lacked access to EHRs and relied on alternative web-based tools typical of patient portals. The proportion of class members who used digital technologies for health purposes varied from small to large. Older and less educated adults had lower odds of belonging to classes characterized by access or engagement in health behaviors. Hispanic and Asian adults had higher odds of belonging to the mobile-dependent class. Individuals without a regular healthcare provider and those who had not visited a provider in the past year were more likely to belong to classes with limited digital technologies access or health use. Discussion:Only one third of US adults belonged to classes that had near complete access to digital technologies and whose members engaged in almost all health behaviors examined. Sex, age, and education were associated with membership in classes that lacked access to 1+ digital technologies or exhibited none to limited health uses of such technologies. Results can guide efforts to improve access and health use of digital technologies to maximize associated health benefits and minimize disparities.

Despite efforts to promote inclusivity in schools, ethnic bullying is a pervasive issue. Recent studies have highlighted the potential of empathy and cultural self efficacy within cross-cultural friendships to mitigate ethnic bullying. Violence prevention programs in the United States rely on didactic approaches and few include embodied approaches. Our goal was to examine the impact of dance/movement therapy (DMT) on empathy, peer relationships, and cultural self-efficacy among racially/ethnically diverse groups of middle school students using a mixed methods research design. Quantitative data did not demonstrate significant change in empathy, peer relationships, and cultural self-efficacy. Qualitative data described an increase in participants’ emotional intelligence including empathy, cultural self-efficacy, and positive cross-cultural relationships. Additional research is needed to determine the definitive impact of DMT on these outcomes.

BACKGROUND:Cytomegalovirus (CMV) commonly reactivates after allogeneic hematopoietic cell transplant (HCT), potentially leading to CMV disease and significant morbidity and mortality. To reduce morbidity and mortality, many centers conduct weekly CMV blood polymerase chain reaction (PCR) surveillance testing with subsequent initiation of antiviral therapy upon CMV DNAemia detection. However, the impact of CMV DNAemia on subsequent hospitalization risk has not been assessed using models accounting for the time-varying nature of the exposure, outcome, and confounders. METHODS:All allogeneic HCTs at the Children's Hospital of Philadelphia from January 2004-April 2017 were considered for inclusion. Patients were monitored with CMV surveillance via PCR testing for up to 105 days after HCT receipt. We estimated the association between CMV DNAemia and rate of hospitalization using marginal structural models (MSM). RESULTS:There were 343 allogeneic HCT episodes in 330 with CMV surveillance; median age was 9.0 (range: 0.1-26.2) and 46.5% were female. And 24.1% of HCT patients had at least one positive CMV blood PCR during the follow-up period. Median time to CMV DNAemia detection was 19 days (range: 4-97). The MSM estimated the incidence rate ratios for an association of CMV DNAemia with hospitalization to be 1.24, (95% confidence interval: 1.04-1.47). CONCLUSIONS:CMV DNAemia was associated with an increased hospitalization in the post-HCT period. The MSM accounted for time-varying nature of the outcome, exposure and confounders. The findings support prevention of CMV DNAemia in this population. We recommend further investigation into the effectiveness and safety of prophylaxis versus pre-emptive CMV prevention approaches.

Background: Electronic health record (EHR) data represent a critical resource for comparative effectiveness research, allowing investigators to study intervention effects in real-world settings with large patient samples. However, high levels of missingness in confounder variables is common, challenging the perceived validity of EHR-based investigations. Methods: We investigated performance of multiple imputation and propensity score (PS) calibration when conducting inverse probability of treatment weights (IPTW)-based comparative effectiveness research using EHR data with missingness in confounder variables and outcome misclassification. Our motivating example compared effectiveness of immunotherapy versus chemotherapy treatment of advanced bladder cancer with missingness in a key prognostic variable. We captured complexity in EHR data structures using a plasmode simulation approach to spike investigator-defined effects into resamples of a cohort of 4361 patients from a nationwide deidentified EHR-derived database. We characterized statistical properties of IPTW hazard ratio estimates when using multiple imputation or PS calibration missingness approaches. Results: Multiple imputation and PS calibration performed similarly, maintaining ≤0.05 absolute bias in the marginal hazard ratio even when ≥50% of subjects had missing at random or missing not at random confounder data. Multiple imputation required greater computational resources, taking nearly 40 times as long as PS calibration to complete. Outcome misclassification minimally increased bias of both methods. Conclusion: Our results support multiple imputation and PS calibration approaches to missingness in missing completely at random or missing at random confounder variables in EHR-based IPTW comparative effectiveness analyses, even with missingness ≥50%. PS calibration represents a computationally efficient alternative to multiple imputation.

Abstract In 2018, the US Food and Drug Administration (FDA) limited the indication for immune checkpoint inhibitors (ICI) in metastatic bladder cancer to patients with programmed cell death protein ligand-1 (PD-L1)–positive tumors. The impact of the label change on survival outcomes remains unknown. We conducted a controlled interrupted time series analysis using a nationwide electronic health record–derived oncology dataset. We used Cox regression to compare mortality in the post- vs prelabel change periods among affected (initiators of ICI or carboplatin-based chemotherapy) vs unaffected (initiators of cisplatin-based chemotherapy) patients. The use of ICI, carboplatin, and cisplatin was similar pre- and postlabel change, but PD-L1 testing increased postlabel change. In adjusted models, survival did not differ after the FDA label change policy compared with prior to the label change in any of the groups. The FDA label restriction on immunotherapy was associated with increased PD-L1 testing but not with changes in treatment patterns or mortality among patients with metastatic bladder cancer.

Abstract Background Our institution provides universal CMV prophylaxis (PPX) for all high (D+/R-) and medium risk (R+) solid-organ transplant (SOT) recipients. We sought to evaluate this practice by assessing CMV infection and disease within the first year of SOT. Methods Retrospective cohort study of all children undergoing first SOT at Children’s Hospital of Philadelphia from January 2012 to October 2017. We identified recipients with CMV infection (detection of CMV DNA in body fluid/tissue with or without symptoms) and disease (symptomatic or tissue-invasive infection) in the first year after SOT. We calculated the rate of CMV infection and compared CMV-free survival based on SOT type and CMV risk using log-rank tests. Results 244 children received 246 SOTs: 90 liver, 70 kidney, 59 heart, 27 lung. In total, 39 children (16%) had 49 CMV infections in the first year after SOT, including 29% of high (n = 21/72) and 23% of medium risk recipients (n = 16/69). The fraction of each organ type with CMV infection was similar (Figure 1, P = 0.33). Among high and medium risk recipients, all of whom received PPX, the incidence rate of CMV infection in the first year post-SOT was similar: 10.1 vs. 7.8/10,000 days (P = 0.22). There were no differences in CMV-free survival by organ (Figure 2, log-rank P = 0.25) or between high and medium risk recipients (Figure 3, log-rank P = 0.46). In total, 22% (n = 10/45) of CMV infections in high/medium risk patients occurred while on PPX; half were in the setting of reduced PPX dosing or within 2 weeks of SOT. Of the 35 CMV infections post-PPX, the median time to detection of CMV after PPX was 39 days (IQR 28–98). There were 11 cases (6 high, 5 medium risk) of CMV disease: 6 CMV syndrome, 2 hepatitis, 2 pneumonitis, 1 GI disease. Valganciclovir was more often used for treatment of asymptomatic infections than for CMV disease (79% vs. 33%, P = 0.03). All-cause mortality in the first year post-SOT was similar among those with and without CMV infections (7.7 vs. 6.3%, P = 0.76) and among those with and without CMV disease (9.1 vs. 5.2%, P = 0.57). Conclusion CMV infection was common in high and medium risk SOT recipients in the first year following SOT, and most infections occurred off of PPX. Our data suggest that the highest risk period for CMV infection is in the first months after PPX, and that monitoring may be most useful after PPX has been stopped or when PPX doses are reduced. Disclosures Kevin J. Downes, MD, Merck: Grant/Research Support, Research Grant; Pfizer: Grant/Research Support.

459 Background: In May 2017, atezolizumab and pembrolizumab (IO) received accelerated approval for first-line treatment of cisplatin-ineligible patients with mUC, irrespective of PDL1 test status. In June 2018, the FDA and EMA restricted IO to cisplatin-ineligible patients with PDL1 positive tumors based on early review of data from confirmatory trials which suggested decreased overall survival in patients with PDL1 negative tumors treated with IO. We assessed the impact of the FDA label change on clinical outcomes of mUC patients in routine care. Methods: We conducted a controlled interrupted time series analysis using the US Flatiron Health electronic health record-derived de-identified database. The study sample included patients from 280 cancer clinics nationwide diagnosed with mUC and compared patients potentially impacted by the label change (cisplatin ineligible patients initiating first-line IO or carboplatin-based chemotherapy) to a comparator group who would have been unaffected by the label change (patients initiating first-line cisplatin-based chemotherapy) from 01 April 2017 to 17 May 2018 (pre-label change) and 20 June 2018 to 01 March 2020 (post-label change), excluding a 30-day wash out period encompassing the time-period between the initial FDA safety alert (18 May 2018) and the official FDA label change (19 June 2018). We used Cox regression to estimate adjusted pre-/post-label change related mortality differences in patients receiving carboplatin-chemotherapy or IO, accounting for secular changes in survival through comparison with the cisplatin comparator group. Results: The study included 829 patients with mUC initiating treatment in the pre-label change period (582 IO or carboplatin, 247 cisplatin) and 1,184 patients in the post-label change period (849 IO or carboplatin, 336 cisplatin), respectively. The use of IO, carboplatin, and cisplatin was similar across time-periods (pre-label change: 44.4%, 25.8%, and 29.8%; post-label change: 48%, 23.6%, 28.4%); while PD-L1 testing increased (6.6% to 28.1%). In adjusted models, there were no differences in survival in any of the groups following the FDA label change policy (table). Conclusions: The U.S. FDA label restriction on first-line immunotherapy was associated with increased PD-L1 testing but was not associated with changes in treatment patterns or improved mortality among patients with mUC.[Table: see text]

Prophylaxis with valganciclovir (VGCV) is used routinely to prevent cytomegalovirus (CMV) infections in at-risk pediatric solid organ transplant (SOT) recipients. However, the rate and factors associated with toxicities in this population are not well-described. We conducted a retrospective cohort study of children undergoing SOT at our hospital from January 2012-June 2018. We evaluated the frequency of hematologic and renal toxicities from day 15 through 1-year post-SOT in relation to antiviral exposures, focused on VGCV prophylaxis. Marginal rate models were used to determine the risk of kidney injury and neutropenia in relation to VGCV prophylaxis. Among 281 SOTs, VGCV prophylaxis was administered on 20.1% of all follow-up days. The incidence rates of kidney injury, leukopenia, and neutropenia were significantly higher during VGCV prophylaxis compared to when no antiviral agents were given. Using multivariable marginal rate models, receipt of VGCV prophylaxis was associated with development of kidney injury (rate ratio [RR] 1.79, 95% confidence interval [CI]: 1.22-2.65) and neutropenia (RR 4.82, 95% CI: 3.08-7.55). VGCV dosing did not impact the development of kidney injury or neutropenia. Toxicities are common with VGCV prophylaxis in pediatric SOT recipients.

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ABSTRACTBackgroundThe COVID-19 pandemic has led to delays in patients seeking care for life-threatening conditions; however, its impact on treatment patterns for patients with metastatic cancer is unknown. We assessed the COVID-19 pandemic’s impact on time to treatment initiation (TTI) and treatment selection for patients newly diagnosed with metastatic solid cancer.MethodsWe used an electronic health record-derived longitudinal database curated via technology-enabled abstraction to identify 14,136 US patients newly diagnosed with de novo or recurrent metastatic solid cancer between January 1 and July 31 in 2019 or 2020. Patients received care at ∼280 predominantly community-based oncology practices. Controlled interrupted time series analyses assessed the impact of the COVID-19 pandemic period (April-July 2020) on TTI, defined as the number of days from metastatic diagnosis to receipt of first-line systemic therapy, and use of myelosuppressive therapy.ResultsThe adjusted probability of treatment within 30 days of diagnosis [95% confidence interval] was similar across periods: January-March 2019 41.7% [32.2%, 51.1%]; April-July 2019 42.6% [32.4%, 52.7%]; January-March 2020 44.5% [30.4%, 58.6%]; April-July 2020 46.8% [34.6%, 59.0%]; adjusted percentage-point difference-in-differences 1.4% [-2.7%, 5.5%]. Among 5,962 patients who received first-line systemic therapy, there was no association between the pandemic period and use of myelosuppressive therapy (adjusted percentage-point difference-in-differences 1.6% [-2.6%, 5.8%]). There was no meaningful effect modification by cancer type, race, or age.ConclusionsDespite known pandemic-related delays in surveillance and diagnosis, the COVID-19 pandemic did not impact time to treatment initiation or treatment selection for patients with metastatic solid cancers.

AbstractBackgroundTwo instruments used to measure adult hepatitis B vaccination coverage in the United States are self-report and antibody to hepatitis B surface antigen (anti-HBs). Estimates based on either of these measures are subject to misclassification when used to determine immunity to hepatitis B. This study presents misclassification-corrected estimates of hepatitis B immune prevalence in the US and compares them to self-report- and antibody-based estimates.MethodsWe used cross-sectional data from the 2015-2016 NHANES cycle on 5,151 adults in the US age 18 and older. Existing literature on long-term immunity after vaccination informed anti-HBs sensitivity as a measure of immunity. Our model incorporated literature-based distributions for sensitivity and specificity using a Bayesian approach to correct for misclassification of true immune status by anti-HBs.ResultsAfter correcting for misclassification, overall adult immune prevalence was estimated at 31.0% (95% credible interval, 27.9% to 34.1%). Anti-HBs prevalence was 6.4 (3.9 to 8.8) and self-report prevalence 2.6 (−0.6 to 5.8) percentage points lower than overall immune prevalence. Among Asian Americans, anti-HBs and self-report underestimated immune prevalence by 15.8% (11.5% to 20.9%) and 25.1% (17.3% to 33.2%), respectively. Among 19 to 25-year-olds, anti-HBs and self-report underestimated immune prevalence by 26.5% (20.7% to 32.5%) and 21.0% (12.6% to 28.9%).ConclusionsBoth self-reported vaccination and antibody-based measures underestimate hepatitis B immunity among adults. This underestimation was especially large among younger adults and Asian Americans. The consequences of treating these surrogates as unbiased measures of vaccination or immunity may only increase as more vaccinated children age into adulthood.

1528 Background: The COVID-19 pandemic has disrupted US healthcare delivery and led to delays in life-prolonging therapy for some conditions. Its impact on diagnosis and timely care delivery for patients (pts) with cancer is unknown. We assessed the pandemic’s impact on time from advanced diagnosis to systemic treatment initiation (TTI) for pts with newly diagnosed advanced solid cancers. Methods: We performed a controlled interrupted time series analysis using the nationwide Flatiron Health electronic health record-derived de-identified database, which originated from ̃280 US cancer clinics. The study sample included pts ≥ 18 years diagnosed with advanced solid cancers from Jan 1-Jul 31 in 2019 or in 2020, excluding a 30-day period (Mar 8-Apr 7) encompassing the start of most state stay-at-home orders. We used Cox proportional hazards models to estimate standardized predicted probabilities of TTI within 30 days of advanced diagnosis before (Jan-Mar) and during (Apr-Jul) the pandemic in 2020, compared to historical controls in 2019, adjusted for age, sex, race, insurance, performance status, and cancer type. Interactions by cancer type and race examined heterogeneity of effects. Results: The study included 12,977 pts (median age 69 yrs [IQR 61-77]; 47.4% female; 59.4% non-Hispanic white). At the time of analysis, fewer advanced cancer diagnoses were recorded in 2020 (Jan-Mar 2,409; Apr-Jul 3,027) than in 2019 (Jan-Mar 2,910; Apr-Jul 4,631). Compared to Apr-Jul 2019, pts diagnosed with advanced cancer during the COVID-19 period were more likely to have de novo (vs recurrent) disease (67.3% vs 56.8%). In adjusted models, the COVID-19 period was associated with an increased probability of treatment within 30 days (adjusted difference-in-differences +5.2 percentage points [ppts]). TTI improvements were not observed for pts with advanced breast cancer or Black pts, but effect differences across subgroups were not statistically significant (Table). Conclusions: Among pts diagnosed with advanced cancer, the COVID-19 pandemic was associated with shorter time to systemic therapy initiation. These treatment patterns may reflect the fewer advanced cancer diagnoses and higher proportion of de novo cancers observed during this period. Longer follow-up and data maturity are needed to understand the impact of the pandemic on clinical outcomes.[Table: see text]