Distinct Recurrence Pattern and Survival Outcomes of Invasive Mucinous Adenocarcinoma of the Lung: The Potential Role of Local Therapy in Intrapulmonary Spread

Background: Invasive mucinous adenocarcinoma (IMA) is distinct from non-mucinous adenocarcinoma, but studies on recurrent IMA are scarce. Thus, this study aimed to evaluate the recurrence patterns of IMA and the role of pulmonary local therapy (LT) in resectable pulmonary recurrence of IMA.Methods: The study reviewed 403 patients with surgically resected IMA between 1998 and 2018. The recurrence patterns were categorized as solitary pulmonary recurrence (SPR), multiple pulmonary recurrence (MPR), and extra-pulmonary recurrence (EPR). The clinicopathologic characteristics, overall survival (OS), and post-recurrence survival (PRS) were analyzed according to the recurrence pattern and LT administration.Results: Recurrences were found in 91 (22.6%) patients, including 18 patients with SPR, 37 patients with MPR, and 36 patients with EPR. Compared with the MPR and EPR groups, the SPR group had a longer disease-free interval (32.5 vs. 9.6 vs. 10.1 months, respectively; p < 0.01) and a better OS (5-year OS: 88.5%, 41.5%, and 22.9%, respectively; p < 0.01). In case of resectable pulmonary recurrence, pulmonary LT was administered to 15 patients with SPR and 3 patients with MPR. These patients showed a better 5-year PRS than the other patients with pulmonary recurrence (86.3% vs. 30.4%; p < 0.01). Notably, long-term survival was observed for one patient with MPR undergoing LT and two patients with SPR undergoing a second LT for a second pulmonary recurrence.Conclusions: In this series, the patients with recurrent IMA showed different prognoses according to the recurrence pattern. The patients with pulmonary recurrence of IMA undergoing LT showed a favorable prognosis, suggesting the potential role of LT for resectable pulmonary recurrence of IMA.