Abstract Background: Clinicians infrequently use geriatric assessment in routine care, despite its superior ability to identify at-risk older adults with early breast cancer compared to clinician-rated Karnofsky Performance Status (cKPS). Asking patients to rate their own performance status may offer a more scalable alternative, but the relationship between patient-reported KPS (pKPS) and treatment outcomes is unknown. We hypothesized that pKPS would show stronger associations with treatment outcomes than cKPS but similar associations as geriatric assessment-based frailty. Methods: The HOPE study enrolled 499 women aged 65y with stage I-III breast cancer across 16 US sites who were planned to start neo/adjuvant chemotherapy. At baseline, we obtained a geriatric assessment-based Deficit Accumulation Frailty Index (DAFI; categorized as robust DAFI 0.2 or prefrail/frail DAFI 0.2). cKPS and pKPS were collected and categorized as high KPS=80 or low KPS70 based on cutoffs consistent with prior studies. Our primary endpoint was grade 3+ toxicity. Secondary endpoints included treatment modifications (dose reductions, dose delays, early discontinuation) and survival (non-breast cancer-specific survival non-BCSS). Kappa statistics were used to evaluate agreement between cKPS and pKPS. Adjusting for age, race/ethnicity, stage, and regimen, multivariable logistic regression was used to evaluate associations of DAFI, cKPS, and pKPS with grade 3+ toxicity and treatment modifications, while Cox proportional and Fine-Gray regression were used to evaluate relationships with non-BCSS. Results: Of the 499 participants (median age 70 65-86), 21% were prefrail/frail, 4% had low cKPS, and 10% had low pKPS. cKPS and pKPS correlated weakly (kappa=0.16). In the adjusted multivariable model, DAFI was strongly associated with all treatment outcomes: grade 3+ toxicity, treatment modifications, and non-BCSS (Table). cKPS was only associated with toxicity and non-BCSS. pKPS was not associated with any outcomes. Conclusion: Although pKPS offers a simpler, more scalable alternative to geriatric assessment, it was not associated with treatment outcomes in this study. Geriatric assessment-derived frailty remained the most robust measure, showing consistent associations with toxicity, treatment modifications, and survival, while cKPS showed limited associations. These findings underscore the need to prioritize the implementation of geriatric assessments in routine oncology practice to improve risk stratification and guide treatment decisions for older adults with breast cancer. Citation Format: Y. Zektser, C. Sun, W. Dale, J. Ji, N. V. Baclig, H. J. Cohen, H. Kim, V. Katheria, C. Lee, M. Sedrak. Comparing Functional Measures and Their Associations with Toxicity and Survival in Older Adults with Early Breast Cancer: Results from the Prospective Multicenter HOPE Study abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-01-14.
Zektser et al. (2026) studied this question.