301 Background: Innovative strategies to mitigate the time toxicity of cancer therapy are desperately needed. We have shown that a text-based e-triage can utilize patient-reported outcomes to identify patients without immune checkpoint inhibitor (ICI) toxicity who could safely fast-track to ICI infusion without a pre-infusion office visit. We report the efficacy of e-triage versus usual care to minimize the time toxicity of cancer care. Methods: This hybrid type 1 effectiveness-implementation randomized controlled trial was conducted at Penn Medicine between December 2021 and December 2022. Eligible patients spoke English, were receiving single agent ICI for a solid tumor, and had access to a mobile device with text messaging. The e-triage arm included ICI toxicity symptom assessment via two-way text messaging 96 hours prior to scheduled ICI and routine laboratory testing. Patients on the e-triage arm with normal bloodwork and no symptoms identified by the e-triage were eligible to fast-track to ICI infusion, bypassing the pre-treatment office visit. Usual care was standard office visits. Primary endpoint was care time (total time per ambulatory encounter including commute-, wait-, infusion-, and lab-times). Secondary endpoints were patient wait time per encounter, incident emergency department (ED) or hospital visits during follow-up, health related quality of life (HRQOL) measured by The Functional Assessment of Cancer Therapy-General, and patient satisfaction measured by PSQ-18. Differences in proportions of ED or hospital visits between arms were evaluated by the Fisher’s exact test. Linear mixed-effects models with random intercepts for each individual evaluated differences in all other endpoints between arms, accounting for within-patient correlation. Implementation outcomes were adoption (# patients who participated in the trial out of # approached) and fidelity (# patients on the intervention arm who followed their triage assignment). Acceptability, feasibility, and appropriateness outcomes were reported previously. Results: Among 152 eligible patients, 51 consented onto study (adoption rate 33.6%) and 40 were randomized (n=21, usual care; n=19, e-triage). Patient characteristics will be presented. Of 52 encounters on the e-triage arm, 23 adhered to their e-triage assessment (fidelity rate 44.2%). Compared with the usual care arm, patients on the e-triage arm had an average of 70 minutes less care time per encounter (95% CI -123.7 to –8.08 minutes, p=0.03) and 30.1 minutes less wait time (95% CI -61 to 1.1 minutes, p=0.08). The incidence of ED or hospital visits did not differ by treatment arm (usual care, n=2, 12.5% vs. intervention, n=3, 20%, p=0.65). HRQOL and patient satisfaction scores were similar by treatment arm. Conclusions: Results from this pilot trial support further work to optimize the design and implementation of a mobile e-triage program to personalize cancer care delivery and minimize time toxicity. Clinical trial information: NCT05134636 .