Abstract Background- Dissemination of cancer cells and their colonization at distant sites (metastases) is the primary cause of death in patients with solid tumors. Despite of popular theories of cancer metastases, there are several lacunae in our understanding of extent of Metastatic Disease at Presentation (MDP). The aim of this study was to evaluate if organ sites could be grouped together based on the available knowledge extent of lympho-vascular communication (LVC) and probable respiratory pressure changes they undergo and whether this correlated with incidence of MDP. Methods- We analyzed a prospectively maintained database of patients with solid tumors presenting between January and December 2017 at our tertiary care cancer center. The tumors were hypothetically divided into four regions (R) depending on extent of LVC and respiratory pressure changes. All patients had clinico-radiological staging after pathological confirmation of cancer. The hypothetical region grouping R1-R4 was independently evaluated by unsupervised k-means clustering. The incidence of MDP was compared in subgroups defined by primary tumor stage, anatomical region, histology, gender, and age using logistic regression. Results- Of 17,467 patients included with median age 54 years, 6714 (38.4%) had MDP. The incidence of M1 disease in R1 vs R2 vs R3 vs R4 regions, older (>50 years) vs younger Conclusion- Primary anatomical regions defined by LVC and respiratory pressure changes; primary tumor histology (type and grade) and male gender are significant determinants of MDP in solid tumors. Region grouping of solid organs based on extent of lymphaticovenous communications and rhythmic respiratory pressure changes and % MDP Citation Format: Rajendra Badwe, Shalaka Joshi, Rohini Hawaldar, Rohan Chaubal, Atanu Bhattacharjee, Vaibhav Vanmali, Nita S. Nair, Sudeep Gupta. Lymphatico-venous communications and rhythmic, respiratory pressure changes influence the incidence of metastatic disease at presentation in solid tumours [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-57.