e13506 Background: In locally advanced cervical cancer (LACC), adding chemotherapy (ChT) to radiotherapy (RT) improves survival but increases toxicity. In the Philippines, about 33% of cervical cancers are diagnosed in the elderly and about 36% present with ureteral obstruction. RT compliance may be compromised by cisplatin toxicity. Shared decision-making (SDM) better engages the patient in the decision-making and implementation planning process. Patient decision aids (PtDA) may increase knowledge and self-efficacy, thereby decreasing decisional conflict and attitudinal barriers and improving treatment compliance. Methods: The Interprofessional Shared Decision-Making Model was used as a conceptual framework. The PtDA defines the index decision, facilitates information exchange and examination of values and preferences, towards the determination of a practicable choice. Using a mixed-methods design and following International Patient Decision Aid Standards (IPDAS) guidelines, a steering panel consisting of radiation oncologists (RO) (2), gynecologic oncologists (GO) (1), oncology nurse (1), clinical psychologist (1), cancer survivor (1), and caregiver (1) developed the CECIL prototype, a PtDA for cisplatin-intolerant LACC patients faced with the decision of adding ChT to RT. The elements were based on the Decision Support Framework and the content, on current international and local guidelines, and a recent systematic review. The prototype was alpha-tested by the steering committee using the e-Delphi method. The PtDR Ottawa Acceptability Practitioner and Patient Questionnaires were used to evaluate comprehensibility, length, amount of information, neutrality, and overall suitability for decision-making. The prototype was then independently evaluated by local internal (RO, 1) and external (GO, 1), and international (RO, 1) reviewers using the IPDAS checklist version 4, which covers 9 relevant domains: information, probabilities, values, guidance, development, evidence, disclosure, plain language, and evaluation. Results: Alpha testing showed high practitioner acceptability (all items with mean and median scores ≥4; overall mean score 4.70/5) and good patient acceptability (all items good to excellent). Content validation showed that the PtDA satisfied all IPDAS qualifying (6) and certification (6) criteria, with high overall mean score (3.63/4) for applicable quality (17) criteria. All reviewers' comments were considered in the subsequent revision of the prototype. Conclusions: The CECIL prototype shows good practitioner and patient acceptability, and content validity on peer review. It will be pilot-tested and subjected to the phase 2 of the clinical trial (NCT05701735) to determine its utility in preparation for decision-making and effectiveness in reducing decisional conflict. Clinical trial information: NCT05701735 .