e18534 Background: PGD are crucial to inform and optimize cancer care. These may include patient-reported outcomes measures (PROMs), patient-reported experience measures (PREMS), or patient preferences information (PPI). The increasing use of PGD has led to the need for the adaptation of instruments to different languages and cultures. Recent data has brought attention to the additional need to consider patients’ ability to understand written information included in PROMs. Low health literacy is associated with higher risk for quality-of-life deterioration and generates disparities, including underrepresentation in cancer research. Aiming at improving equity and representation, we evaluated readability and understandability of nine French-language PROMs that are currently used in a contemporary cohort of breast cancer survivors. Methods: Readability of PROMs was assessed using the Flesh Reading Ease Score (FRES), the Gunning’s Fog Index (FOG), and the FRY graphics (yielding a mean score representing the n. of school years required to understand the respective text). Readability was considered ideal if mean score ≤6th grade level and acceptable if between 6-8th grade. Understandability was evaluated using the Patient Education Materials Assessment Tool (PEMAT, range 0-100%, higher scores corresponding to easier understandability) and defined as ideal if PEMAT ≥ 80%. Plain-language best practice was met if both readability and understandability were ideal. The Evaluative Linguistic Framework for Questionnaires (ELF-Q) provided additional qualitative elements to assess understandability. Two native French speakers, including a patient representative, independently evaluated each PROM. An additional independent assessment was requested if discordance. Results: None of the 9 PROMs evaluated had ideal readability scores, and only 1 had an acceptable score. Understandability ranged from 55-91%, and only 3 PROMs had ideal scores. None of the instruments met the definition of plain-language best practice. ELF-Q identified points for improvement in several dimensions of the PROMs (Table). Conclusions: The use of comprehensive linguistic and cultural frameworks during the development and translation of self-reported PGD instruments may improve experience and engagement of patients with lower literacy and foster equity and representation in cancer cohort studies. [Table: see text]