Clinical features and prognosis of resectable pulmonary primary invasive mucinous adenocarcinoma.

Background: According to the latest the World Health Organization (WHO) classification in 2015, invasive mucinous adenocarcinoma (IMA) is defined as a new pathological subtype of lung adenocarcinoma (LUAD). However, whether this rare subtype of lung pathology has any difference in prognosis than conventional LUAD is debatable. Our study attempted to compare clinical characteristics and prognosis of IMA vs. noninvasive mucinous adenocarcinomas (NMA). Methods: A total of 1,857 patients with LUAD who underwent radical resection were screened from 2010 to 2015 at Zhejiang Cancer Hospital. Patients with pulmonary IMA were matched 1:1 by using propensity scores with LUAD adjusted for clinicopathological characteristics. After follow-up, overall survival (OS) and disease-free survival (DFS) were explored by Kaplan-Meier and Cox regression analyses. Forest plots were used for subgroup analyses. Results: Following screening, 499 patients with LUAD were enrolled, with 97 IMA and 402 NMA. Compared to NMA of the lung, IMA was proportionately lower in women (50.5% vs. 63.4%; P=0.026) and nonsmokers (P<0.001). IMA was also associated with earlier tumor stage I (68.0% vs. 55.5%; P=0.033) and lower frequency of upper lobe tumors compared to NMA (P=0.007). Following propensity score matching, 97 pairs were selected, among which we found that patients with pulmonary IMA had a longer OS than those with NMA (P=0.014). According to the subgroup analysis, improved OS in the IMA cohort versus the NMA cohort was observed across various factors, including the absence of lymphovascular invasion or perineural invasion. Conclusions: In this study, we found that resectable IMA patients had a better OS than NMA patients. This study contributes to the understanding of IMA in depth, but it needs to be validated through additional multicenter studies.