Introduction: During cancer treatment the timely detection and management of adverse events is essential for patient safety and maintaining the quality of life. Electronic patient self-Reporting of Adverse events: Patient Information and aDvice (eRAPID) was devised to support oncology practice, by allowing patients to self-report symptoms online at home during and beyond cancer treatment. Fundamentally the eRAPID intervention delivers immediate severity-tailored feedback directly to patients to guide self-management strategies or hospital contact. Patient data are available in electronic health records for hospital staff to access and review as part of clinical assessments. Methods for Interpreting and Addressing Patient-Reported Outcome (PRO) Scores: The eRAPID intervention has 5 main interconnecting components (clinical integration into standard care pathways, patient symptom reports, self-management advice, information technology, and staff/patient training). Following guidance for the development of complex interventions and using a mixed methods approach, eRAPID was created through a number of stages and tested in a series of usability settings before undergoing systematic evaluation in a randomized controlled trial. These developmental stages are described here with a focus on how decisions were made to enhance patient and professional engagement with symptom reports and encourage interpretation and clinical utilization of the data. Discussion: Clinically embedded PRO interventions involve a number of elements and stakeholders with different requirements. Following extensive developmental work eRAPID was pragmatically designed to fit into current oncology practices for reviewing and managing chemotherapy-related toxicities.