Casperson, Mallory

1564 Background: Adolescent and young adult (AYA) females with early-stage ER-negative and/or HER2-positive breast cancer commonly receive chemotherapy to reduce risk of recurrence. Fertility concerns, counseling, and preservation may influence chemotherapy decisions and time to chemotherapy (TTC) initiation. Methods: We surveyed AYA survivors of stage I–III premenopausal ER-negative and/or HER2-positive breast cancer treated at Kaiser Permanente Northern and Southern California (2013-2022). Fertility concerns were defined as not having completed desired family size or being unsure about having completed desired family size at diagnosis. We summarized receipt of fertility counseling, receipt of chemotherapy, and use of oocyte/embryo cryopreservation for fertility preservation (FP). Among fertility-concerned patients who received chemotherapy, TTC (days from diagnosis) was assessed separately for neoadjuvant chemotherapy (NAC) vs for adjuvant chemotherapy (AdjC). Time to NAC was natural log–transformed and modeled with multivariable log-linear regression to estimate relative differences in TTC, adjusting for stage, study site, ER, HER2, age, and diagnosis year. Results: Of 363 respondents, 197 (54%) had fertility concerns at diagnosis; 183/197 (93%) received chemotherapy, similar to 153/166 (92%) among those without concerns (p=0.7). Of the concerned chemotherapy recipients, 45 (25%) saw a fertility specialist but did not pursue FP while 55 (30%) underwent FP. For the 112 fertility-concerned NAC recipients, FP was associated with longer TTC than no fertility specialist counseling (mean=41 vs. 30 days; adjusted ratio=1.39; 95% CI 1.15–1.69), whereas fertility specialist counseling without FP was not (mean= 31 vs. 30 days, adjusted ratio=1.04; 95% CI 0.86–1.25). For the 71 fertility-concerned AdjC recipients, TTC was similar for patients who did not see a fertility specialist (mean=63 days), those who froze oocytes/embryos (mean=65 days), and those who saw a fertility specialist but did not pursue FP (mean=69 days). Conclusions: In this AYA breast cancer cohort, there was no evidence that fertility concerns led patients to decline chemotherapy. FP was associated with a modest delay in NAC initiation (<2 weeks on average). Time to chemotherapy (TTC) among 183 AYA patients with ER− and/or HER2+ breast cancer and fertility concerns. Fertility-focused care N (n=183) Neoadjuvant chemotherapy (n=112) Mean TTC, days Relative difference in TTC, adjusted ratio (95%CI) Adjuvant chemotherapy (n=71) Mean TTC, days No fertility counseling from a specialist 83 (45%) 55 (49%) 29.6 Reference 28 (39%) 62.6 Received fertility counseling from a specialist No fertility preservation 45 (25%) 28 (25%) 30.7 1.04 (0.86,1.25) 17 (24%) 68.6 Fertility preservation 55 (30%) 29 (26%) 41.2 1.39 (1.15,1.69) 26 (37%) 64.6

Abstract Breast cancer (BC) is the most common cancer among female adolescents and young adults (AYAs; 15-39 years). While advances in treatment have improved survival, cardiovascular disease (CVD) can result from systemic therapies, and CVD is a leading cause of death in AYA cancer survivors. AYAs with BC face nearly a four-fold increased risk of CVD compared to their peers without cancer. However, data on the effects of systemic treatment on CVD in this population remains limited. We estimated risk of CVD in AYAs diagnosed with invasive BC (2006-2020), who survived ≥2 years, and were diagnosed and treated in the Kaiser Permanente (KP) Northern and Southern California. Patients were categorized by receipt of anthracycline-, alkylating-, HER2-, platinum-, and taxane-based therapies within 2 years of diagnosis. We examined the cumulative incidence of CVD starting 2 years post-diagnosis and used Cox proportional hazards regression to determine factors associated with CVD. Among 3,071 AYAs, 35.1% were non-Hispanic (NH) White, 31.6% were Hispanic, 18.3% were NH Asian, and 8.2% were NH Black. Most received systemic therapy (90.6%), including anthracycline- and alkylator without HER2-targeted therapy (41.9%) and HER2-targeted therapy without anthracycline (20.9%). Fewer AYAs received a taxane and alkylator (13.0%) or anthracycline with alkylator and taxane along with a HER2-targeting agent (6.4%). Mean follow-up after cancer diagnosis was 7.2 years (range: 2.0-17.5). The 10-year cumulative incidence of CVD was highest among AYAs who received anthracycline/alkylator/taxane/HER2-targeting therapy (19.6%), intermediate for those with anthracycline/alkylator without HER2-targeting therapy (13.0%) and those who received HER2-targeted therapy without anthracycline (14.6%), and lowest for those who received taxane/alkylator (7.3%). In the multivariable model adjusted for demographic factors and radiation, compared to taxane/alkylator, anthracycline/alkylator/taxane/HER2-targeting therapy (hazard ratio (HR)=2.63, 95% confidence interval (CI) 1.56-4.43); anthracycline/alkylator without HER2-targeting therapy (HR=1.75, CI 1.13-2.71); and HER2-targeting therapy without anthracycline (HR=2.13, CI 1.11-4.09) were associated with an increased risk of CVD. CVD risk was similar for taxane/alkylator and no systemic therapy. Other factors associated with higher risk of CVD included NH Black race/ethnicity (HR=1.90, CI 1.32-2.73 vs. NH White) and public health insurance (HR=1.67, CI 1.00-2.78 vs private). This study identifies AYA BC survivors at higher risk of CVD based on treatment regimens received, with highest risks found for those receiving anthracycline/alkylator/taxane/HER2 treatment combinations. In addition, AYAs of Black race/ethnicity and those with public health insurance experienced more CVD, underscoring the need for targeted interventions to mitigate these disparities. Citation Format: Theresa H. M. Keegan, Candice A. Sauder, Ann M. Brunson, Renata Abrahao, Anne C. Kirchhoff, Eric Haupt, Mallory Casperson, Ted Wun, Chun R. Chao, Andrew B. Smitherman, Hazel B. Nichols, Jessica Chubak, Erin E. Hahn, Lawrence H. Kushi, Kathryn J. Ruddy. Systemic therapy and cardiovascular disease in adolescent and young adult breast cancer survivors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5219.

Abstract Background Few studies have assessed the burden of chronic medical conditions in adolescent and young adult (AYA) cancer survivors. This study estimated the risk of these conditions among AYA survivors compared to a matched cohort without cancer. Methods This retrospective cohort study included 2‐year survivors ( n = 14,917) of 11 common AYA (15–39 years) cancers diagnosed at the integrated health care organizations of Kaiser Permanente (KP) Southern and Northern California during 2006–2020. A comparison cohort ( n = 149,164) without cancer (matched 10:1 by age, sex, calendar year, and KP site) was included. Cumulative incidence (CMI) accounting for death as a competing risk was calculated. Poisson regression estimated the incidence rate ratio (IRR) of each condition in cancer survivors versus the matched cohort, adjusting for age, sex, and race/ethnicity. Results The 5‐year CMI was highest for thyroid (17.4%), respiratory (6.6%), cardiovascular (5.0%), and liver (4.8%) diseases. At 10 years, the CMI of any condition was 39% in survivors versus 26% in the matched cohort. Survivors had a 2‐fold increased risk of being diagnosed with any medical condition (IRR, 2.0; 95% confidence interval [CI], 1.9–2.0) as well as two or more conditions (IRR, 2.3; 95% CI, 2.2–2.5). Risk was highest among survivors of hematologic cancers and those diagnosed with distant stage disease. Elevated risks were observed within all sociodemographic groups of this insured population. Conclusion AYAs with cancer had a higher risk of chronic medical conditions compared to those without cancer. Long‐term surveillance, risk mitigation through lifestyle modifications and effective disease management are crucial to reduce premature mortality.

PURPOSE Survivors of adolescent and young adult (AYA)-onset cancers require comprehensive cancer surveillance care. Guidelines recommend 1-4 clinician visits annually for 5 years depending on stage and disease. The goal of this study was to identify factors associated with patterns of post-treatment primary and oncology care in a large cohort of survivors of AYA-onset cancers diagnosed within an integrated health care system. METHODS Patients diagnosed with cancer between 2006 and 2020 age 15-39 years were included. Surveillance visits were identified from electronic medical records 2-5 years after diagnosis. Multivariable logistic regression was used to assess associations with zero oncology specialty visits. RESULTS Of 7,925 survivors, 46% were Hispanic, 6% non-Hispanic Black, 11% non-Hispanic Asian, 35% non-Hispanic White, and 65% female. One-quarter had no oncology specialty visits in the first surveillance year rising to 38% in year 5; 31% had 3+ visits in the first year, declining to 13% in year 5. Over the surveillance period, 17% did not have any oncology specialty visits and 6% had no primary care or oncology visits. Those who were male (odds ratio [OR], 1.21 [95% CI, 1.02 to 1.45]), 20-24 years at diagnosis (OR, 1.58, 95% CI, 1.27 to 1.9; v 35 to 39), or non-Hispanic Black (OR, 1.38, 95% CI, 1.05 to 1.82; v non-Hispanic White) or had high-deductible commercial or Medicaid insurance (OR, 1.35, 95% CI, 1.15 to 1.59; OR, 1.42, 95% CI, 1.11 to 1.82, respectively; v no or low deductible commercial) were more likely to be in the 0-visit group for oncology specialty care. CONCLUSION Although the majority of this cohort received either primary or oncology specialty care, our study identifies those who may need tailored outreach for follow-up care. Continued research into development and testing of interventions to improve uptake of appropriate health care for survivors of AYA-onset cancers is critical.