Pulmonary interstitial lymphography: A prospective trial with potential impact on stereotactic ablative radiotherapy planning for early-stage lung cancer

•Pulmonary interstitial lymphography is feasible to identify primary nodal drainage.•Contrast was visualized in all patients; drainage frequently involved N1/N2 nodes.•Exploratory primary nodal drainage-inclusive SABR plans met RTOG 0813 constraints. This prospective feasibility trial investigated pulmonary interstitial lymphography to identify thoracic primary nodal drainage (PND). A post-hoc analysis of nodal recurrences was compared with PND for patients with early-stage lung cancer; larger studies are needed to establish correlation. Exploratory PND-inclusive stereotactic ablative radiotherapy plans were assessed for dosimetric feasibility.