Background: Older adults with cancer are at increased risk of treatment-related toxicities and excess mortality. We evaluated whether a patient-reported geriatric assessment (GA) based frailty index can identify those at risk of adverse outcomes. Methods: Older adults (≥60 years) enrolled in a single-institutional prospective registry underwent patient-reported GA at initial evaluation in our medical oncology clinic. Using deficit accumulation method, we constructed a 44-item frailty index (CARE-FI), categorizing patients as robust, pre-frail, and frail. The primary outcome was overall survival (OS). Secondary outcomes included (a) functional decline at 3 months post-therapy (b) incident grade ≥3 treatment-related toxicities at six-month post-treatment. We used multivariate Cox and logistic regression models respectively to study the impact of frailty on primary and secondary outcomes. Results: We identified 589 older adults with a median age of 69 years; 55% males and 73% Whites. Overall, 168 (29%) were pre-frail and 230 (39%) frail. Being frail (vs. robust) was associated with worse OS (Hazards Ratio, HR 1.83, 95% Confidence Interval, CI 1.34–2.49, p < 0.001) after adjusting for age, sex, race/ethnicity, cancer type, cancer stage, and line of therapy. Similarly, frailty was associated with increased risk of functional decline (OR 3.01; 95% CI 1.33–6.81; p = 0.008) and grade ≥3 non-hematologic toxicities (OR 3.65; 95% CI 1.54–8.69; p = 0.003) but not hematologic toxicities (OR 1.01; 95% CI 0.46–2.22; p = 0.97). Conclusions: Our frailty index using a patient-reported GA is a robust predictor of survival, functional decline, and treatment related toxicity among older adults with GI malignancies.
