OBJECTIVE: The Laudo Estruturado e Léxico em Oncologia (LELEX, Lexicon and Structured Reporting in Oncology) initiative was established to develop a standardized lexicon and structured reporting system applicable across cancer types.
METHODS: The São Paulo Radiology Society and Brazilian Society of Medical Oncology assembled a 27-member multidisciplinary consensus panel that included radiologists, medical and radiation oncologists, surgeons, and a patient representative. A literature review identified relevant oncologic reporting frameworks to guide the creation of a draft template and lexicon by the LELEX executive committee. Panelists were surveyed to assess current reporting practices and preferences between free-text and structured reports. Consensus (i.e., agreement by more than 80% of panelists) on the final lexicon and reporting system was reached through post-survey panel discussions.
RESULTS: Compared with a traditional free-text report, a structured report incorporating the LELEX lexicon received significantly higher ratings for precision and was deemed better for guiding clinical decisions by > 88% of panelists. In post-survey discussions, consensus was achieved for all lexicon components, including diagnostic certainty terms, lesion count descriptors, and longitudinal comparison language. The structured report template was also agreed upon by the panel members.
CONCLUSION: The LELEX initiative established a consensus-driven structured reporting system and lexicon for general oncologic imaging baseline and follow-up assessments.

Keywords: Radiology information systems; Radiology/education; Medical records/standards; Terminology as topic; Neoplasms/diagnostic imaging; Medical oncology/education; Decision making; Uncertainty; Longitudinal studies; Follow-up studies.