Background: Oral cancer (OC) remains a major public health challenge, characterized by high morbidity and mortality rates and a predominance of late-stage diagnoses, particularly in low- and middle-income countries. From a sociodemographic perspective, alcohol and tobacco consumption are most prevalent among socially and economically vulnerable groups, who also face substantial barriers to accessing health services, ultimately contributing to delayed diagnosis. In this context, implementing effective early detection strategies becomes eincreasingly  urgent. Objective: This study evaluated the performance of different strategies to expand access to preventive oral examination (POE) among vulnerable populations within the public health system of Rio de Janeiro, Brazil. Methods: This randomised clinical trial was conducted by the School of Dentistry of the Federal University of Rio de Janeiro (FO-UFRJ), in partnership with the Municipal Health Department of Rio de Janeiro (SMS-RJ). The study protocol was approved by the Research Ethics Committees of FO-UFRJ (No. 6.030.135) and SMS-RJ (No. 6.390.106) and registered on ClinicalTrials.gov (NCT06231537). The trial was conducted between January and December 2024 across 35 primary health care (PHC) units in Rio de Janeiro, Brazil. Adults aged ≥35 years identified as tobacco users in the public electronic medical record system were included and considered at high risk for POE. PHC units were allocated to three groups: control (opportunistic screening without active invitation; 12 units), experimental I (organized invitation for POE plus home-visit support; 11 units), and experimental II (organized invitation for POE plus an awareness campaign; 12 units). Results: The 23 PHC units implementing organized screening included 2,735 registered tobacco users, whereas the 12 units maintaining opportunistic screening included 1,048. Consequently, POE coverage reached 77.2% in the organized screening arms versus 3.6% under opportunistic screening (p < 0.05). POE adherence was higher with organized invitation plus community awareness (77.2%) than with home-visit support (58.1%). Biopsies from organized screening showed higher positivity for oral potentially malignant disorders (40.0%) and OC (33.3%) compared with biopsies from individuals not registered as tobacco users or younger than 35 years (13.6% and 4.8%, respectively; p < 0.0001). Conclusions/Implications: Organized, invitation-based screening integrated into PHC substantially expanded access to early diagnosis among high-risk and socially vulnerable individuals who would otherwise remain unscreened. Compared with an opportunistic approach, this strategy increased the detection of malignant and potentially malignant oral lesions. The model proved sustainable within routine primary healthcare services, requiring no additional workforce and minimal disruption to existing workflows, and represents a scalable strategy to improve access to early oral cancer diagnosis.

Graphical Abstract