577 Background: Prostate specific membrane antigen positron emission tomography (PSMA-PET) increases the detection of metastatic prostate cancer relative to conventional imaging. To understand whether PSMA-PET is associated with greater use of therapies for metastatic disease we evaluated initial treatment among contemporary commercial insurance beneficiaries undergoing staging evaluation for prostate cancer. Methods: We conducted a retrospective cohort study among Blue Cross Blue Shield insurance beneficiaries with an incident diagnosis of prostate cancer from July 1st, 2021, through March 31, 2023, who received either PSMA-PET or bone scintigraphy imaging in the six-month period before and after diagnosis based on billing codes. The primary study outcome was the receipt of androgen pathway receptor inhibitor (ARPI) therapy in the one-year period following diagnosis using national drug codes. Secondary outcomes included local therapy and androgen deprivation therapy (ADT) use. Chi-square (χ²) tests were used to compare distributions of treatment by imaging modality. We used mixed effects logistic regression to examine the association between imaging modality (PSMA-PET versus bone scan) and initial treatment, accounting for beneficiary age, diagnosis period, comorbidity, frailty, local therapy, census region, and social deprivation index for clustering of beneficiaries within hospital referral regions. Results: Among 4,952 beneficiaries newly diagnosed with prostate cancer, 3,690 received bone scans and 1,262 received PSMA-PET imaging. The median age in both groups was 62 years. Patients receiving PSMA-PET were less likely to undergo radical prostatectomy. (40.8% versus 48.1%, χ² p<0.001) than beneficiaries imaged with bone scan. Receipt of ARPI was more common among beneficiaries who received a PSMA-PET scan (25.0%) versus bone scan (9.7%, χ² p<0.001). ADT use was also more common in PSMA-PET imaged versus bone scan imaged individuals (58.9% versus 39.4%, χ² p<0.001). PSMA-PET was independently associated with use of initial ARPI therapy, (odds ratio vs bone scan: 3.83, 95% confidence interval 3.11-4.71, p<0.001). Conclusions: In this claims-based study of a single large U.S. commercial health insurer, receipt of PSMA-PET was associated with increased use of therapies for metastatic prostate cancer. These findings highlight the growing role of molecular imaging in the diagnostic landscape of prostate cancer, and support further efforts to estimate effects of imaging on clinical outcomes and healthcare costs.

490 Background: In response to efficiency concerns, the NCI cooperative group trial system was redesigned in 2014 to streamline trial design and conduct. As timely evidence is vital to high-quality cancer care, we examined trial accrual and timeliness in recent NCI cooperative group trials, focusing on meeting accrual targets and time to completion. Methods: We used the Aggregate Analysis of ClinicalTrials.gov (AACT) database to identify phase II or III interventional trials that were initiated between 2011 and 2019 and had an NCI cooperative group listed as the sponsor, responsible party, or principal investigator. To assess a study’s time to completion, we quantified the time between its “start date” and “primary completion date” (date when the final data to fulfill the primary outcome were ascertained) listed on ClinicalTrials.gov. The primary outcome was trial primary completion within 5 years of initiation (for trials initiated before 2019); we also assessed 8-year trial completion (for trials initiated prior to 2016). To examine the timeliness of recent NCI cooperative group trials, we used chi-square tests and adjusted logistic regressions to compare the five-year completion status of trials initiated in 2011–2013 (T1: prior to the 2014 redesign of the National Clinical Trials Network (NCTN)) versus 2016–2018 (T2: after NCTN redesign), adjusting for trial phase and cancer type. A subgroup analysis was conducted among phase III trials. Results: We included 323 studies, and 196 were classified as phase II, 17 were phase II/III, and 110 were phase III. Hematologic (n=49), breast (n=36), and non-small cell lung (n=39) were the most common cancer types researched. NRG Oncology (n=75), Alliance for Clinical Trials in Oncology (n=64), and Eastern Cooperative Oncology Group (n=61) were the most represented cooperative groups. Overall, 40 studies had a final study status of either terminated (0.8%), withdrawn (0.2%), or unknown (0.2%). 50.2% of studies reached their primary outcome within five years (24.5% of phase III and 62.2% of phase II trials). Among the 194 studies initiated prior to 2016, 147 (75.8%) were completed at 8 years (60% of the 70 phase III trials; 84.8% of the 112 phase II trials). Of the 2011–2013 (T1) trials (n=119), 5-year completion status was 46.2%, compared to 58.9% of the 95 studies in T2 (p=0.09). Among phase III trials, the 5-year completion status was 25.6% (T1) and 28.5% (T2) (p=1.00). Adjusting for trial phase and cancer type, there was no significant association between time period and five-year completion status (Odds ratio for T2 vs T1: 1.27; 95% CI: 0.66 to 2.48). Conclusions: Half of NCI cooperative group trials reached primary completion within 5 years, with only one quarter of phase III trials completed in this same time frame. There was no significant improvement in time to completion of phase III trials after the 2014 NCTN redesign, although the COVID epidemic may have hampered trial conduct during the latter time period.

273 Background: Racial and ethnic groups underrepresented in medicine (URiM) comprise 31% of the US population but 8% of oncologists. Although there have been initiatives to increase diversity of the oncology workforce, recent challenges have raised concerns over the degree to which the oncology workforce will be reflective of the broader population in the coming years. This has implications for patient access to concordant physicians and quality of cancer care. This modeling study projects the racial and ethnic diversity of the cancer physician workforce through 2060 under three distinct scenarios. Methods: We used data from the American Medical Association (physician specialty and age) linked to data from the Association of American Medical Colleges (physician self-reported race and ethnicity). We classified cancer oncology specialties as Medical, Radiation, and Surgical Oncology, General Surgery, and Palliative Care. URiM was defined as American Indian/Alaska Native (AIAN), Black, Hispanic, or Native Hawaiian/Pacific Islander (NHPI). We determined the URiM distribution of the oncology workforce in 2020 and created stock and flow models to project changes by decade from 2030 to 2060, factoring in inflows from graduating trainees and expanded training slots, and outflows due to retirement. We modeled three scenarios with varying trends in the growth rate of URiM trainees: Baseline (URiM distribution remains the same as 2020 levels); Trajectory (distribution changes each decade at the same rate of change observed from 2010-2020); and Doubling (URiM growth occurs at twice the rate of non-URiM). Results: In 2020, there were 66,450 practicing cancer care physicians. Of these, 11.3% identified as URiM (9.7% of medical oncologists, 8.8% of radiation oncologists, 8.3% of surgical oncologists, 12.3% of general surgeons, 11.5% of palliative care physicians). The trend sample from 2010-2020 of physicians within 5 years of training completion showed a +1.2% increase in URiM representation (11.7%–12.9%), +1.2% in Hispanic (6.2%–7.4%), and +0.05% in Black (4.95%–5.00%). In the baseline scenario (no change in the % URiM trainees), in 2060, an estimated 12.5% of the workforce would be URiM, compared to 43.2% of the US population (Table). Continuing 2010-2020 trends would raise URiM representation to 16.5% in 2060. Doubling URiM growth would reach 19.1%. Achieving census parity would require increasing URiM trainee representation by 8% per decade. Conclusions: Achieving oncology physician workforce alignment with U.S. demographics by 2060 will require deliberate, systemic action—not just incremental change. 2060 Oncology workforce composition by scenario. Baseline (%) Trajectory (%) Doubling (%) US 2060 Population (%) AIAN 0.5 0.2 0.8 0.7 Asian 27.5 31.4 25.4 9.6 Black 4.9 5.1 7.5 14.1 Hispanic 7.0 11.2 10.7 28.2 NHPI 0.12 0.00 0.19 0.27 White 60.0 52.1 55.5 47.2 URiM 12.5 16.5 19.1 43.2

363 Background: In families of children with cancer, household material hardship (HMH) and health literacy challenges are associated with increased parent distress and lower care satisfaction, respectively. We aimed to describe how HMH and health literacy challenges may influence the advanced childhood cancer care experience. Methods: We conducted a secondary analysis of data collected at 8 U.S. hospitals, using the “Pediatric Cancer Care Experience” (PACE) questionnaire, which was completed by parents/caregivers of children with advanced, or incurable, cancer. We defined HMH as self-reported difficulty with at least one of four domains (housing, food, utilities, and/or transportation) and further characterized the number of HMH domains (0, 1, or >2). We defined health literacy challenges as an affirmative response to at least one of two validated screening questions. To capture key elements of the care experience, we employed three subscales as our primary outcomes of interest: (1) therapeutic alliance, (2) collaborative care, and (3) prognostic communication and shared decision making. Each subscale was comprised of items from PACE with 5-point Likert responses. We computed mean response scores for each subscale across the entire cohort. We then conducted bivariate analyses to explore associations between HMH, parent/caregiver health literacy, and subscale scores. Results: Among 158 respondents, a majority were female (70%), non-Hispanic White (56%), and spoke English as their first language (89%). Over one-third (37%) experienced HMH, with hardship most often reported in >2 domains (n = 40/59, 68%). The most common HMH domain was housing (32%) followed by food (24%), utilities (18%), and transportation (10%). Thirty-eight percent of the cohort reported health literacy challenges, with a higher frequency among respondents who speak a first language other than English (p = 0.010). Care experience subscale scores did not vary significantly by HMH. However, respondents reporting health literacy challenges had lower mean scores for all three subscales, compared to respondents who did not report health literacy challenges: therapeutic alliance (mean subscale score 4.51 [95% CI 4.37, 4.66] vs. 4.78 [4.72, 4.85], p < 0.01), collaborative care (4.55 [4.42, 4.68] vs. 4.76 [4.68, 4.83], p = 0.01), and prognostic communication and shared decision making (4.13 [3.96, 4.31] vs. 4.48 [4.39, 4.58], p < 0.01). Conclusions: Care experience, as measured by PACE subscales characterizing therapeutic alliance, collaborative care, and prognostic communication and shared decision-making, did not vary significantly with HMH but was reduced in the setting of family-reported health literacy challenges. Findings suggest that interventions to support families facing health literacy challenges may improve the advanced cancer care experience.

285 Background: Digital breast tomosynthesis (DBT) has shown improved breast cancer detection over digital mammography (DM) in trials of women aged 46-69. However, its benefit of early detection for older women and its effectiveness in detecting more difficult-to-detect invasive lobular carcinomas (ILCs) remain uncertain. We hypothesized that, among women aged ≥67, DBT may detect tumors at smaller sizes and detect more ILCs compared to DM, and that these benefits would extend to women aged ≥75. We also hypothesized that DBT would detect ILCs at smaller sizes than DM. Methods: This was a retrospective SEER-Medicare cohort study of women aged ≥67 diagnosed with screen-detected ER+/HER2- breast cancer between 2015 to 2019. Screen-detected cases were identified using a validated claims-based algorithm. The primary exposure was screening modality (. The primary and secondary outcomes were tumor size at diagnosis (categorized in 10-mm intervals from 0–10 to ≥51 mm) and histology (ILC vs. other histology), respectively, and their associations with screening modality were assessed using ordinal and multivariable logistic regression. An interaction term was included to evaluate whether DBT is associated with detecting ILCs at smaller sizes. Results: Among 12,582 women, half (49.2%) received DBT at cancer detection. The majority were non-Hispanic White (82.4%), not dual eligible for Medicare and Medicaid (89.5%), and between ages 67 and 75 (55.8%). Among DBT-detected cases, 41.2% of tumors were ≤10 mm, compared to 37.8% among DM-detected cases (P < 0.001). multivariable analyses, DBT was associated with 9% higher odds of detecting smaller tumors compared to DM (aOR: 1.09, CI: 1.01-1.17), but this association was not observed in women aged ≥75 (aOR: 1.01, CI: 0.91-1.13). DBT was also associated with 25% higher odds of detecting ILC compared to DM (aOR: 1.25, 95% CI: 1.12–1.39), and this association persisted among women aged ≥75 (aOR: 1.22; CI: 1.04–1.43). No significant interaction was observed between screening modality and tumor histology on tumor size. Conclusions: Our findings support the use of DBT as a routine screening modality for women aged 67-74 to improve the detection of ILCs. However, DBT did not demonstrate a significant advantage over DM in detecting smaller tumors among women aged ≥75, nor did it detect ILCs at smaller tumor sizes, which suggests that it may not facilitate earlier detection in this age group.

39 Background: Skeletal related events (SREs) are a set of morbidities resulting from metastatic bone disease, including pathologic fracture, spial cord compression, and others. Clinical practice guidelines recommend use of bone modifying agents (BMAs) to prevent SREs for patients with metastatic castration resistant prostate cancer (mCRPC), and against their use for SRE prevention in metastatic castration sensitive prostate cancer (mCSPC). Whether these drugs are delivered in a consistent, guideline-concordant manner across oncology providers has not been described. Methods: We conducted a multicenter, retrospective, cohort study of patients diagnosed with prostate cancer metastatic to bone during 2020-21. The sample included three large health systems in the US Northeast (two community-based networks and one academic cancer center), collectively employing > 1700 physicians and treating > 800 cases of high-risk and/or metastatic prostate cancer each year. Patient comorbidities, timing of emergence of CRPC, and dates of BMA initiation (zoledronic acid or denosumab) were ascertained via chart review. The primary outcomes were BMA overuse during CSPC (defined as BMA initiation prior to emergence of CRPC, among patients without a comorbid condition for which BMA therapy may be appropriate: osteoporosis, osteopenia, or osteoporotic fracture) and appropriate use during CRPC (defined as BMA initiation subsequent to emergence of CRPC). Results: There were 153 eligible patients, 51 from each health system. The median age was 72 years (IQR 65, 80), PSA at diagnosis was 110 (IQR 16, 720), and time from diagnosis to development of CRPC was 352 days (IQR 224, 453). At diagnosis, 14 (9%) patients had documented osteoporosis or osteopenia and 22 (14%) had prior osteoporotic fracture. Among 106 patients assessable for overuse during CSPC, 17 (16%) received BMA (ranging from 13%-21% among the three systems). Among 65 patients who developed CRPC, 32 (44%) had initiated BMA therapy prior to death or most recent follow-up. There was greater variation in use during CRPC, ranging from 22%-54% across the three systems. In time-to-event analysis, at 2 years after emergence of CRPC 52% of surviving patients had initiated BMA therapy (ranging from 30%-66% among the three systems). Conclusions: Overuse of BMAs appeared consistently low. However, guideline-concordant use for patients with metastatic CRPC may vary substantially among clinicians and healthcare systems. This degree of variation suggests that some patients with mCRPC who may benefit from BMA therapy do not receive it. Interventions to reduce these discrepancies and increase appropriate care may improve patient outcomes.