Prognosis in resected invasive mucinous adenocarcinomas of the lung: Related factors and comparison with resected nonmucinous adenocarcinomas

Introduction: In the 2015 World Health Organization classification, invasive mucinous adenocarcinoma (IMA) is categorized as one of various subtypes of lung invasive adenocarcinoma (ADC). However, no comprehensive analysis regarding the clinicoradiologic and prognostic features of IMA has been reported. We aimed to report prognostic factors in IMA and to compare the prognosis of IMAs with that of nonmucinous ADCs. Methods: We included 81 patients with a solitary IMA of the lung and analyzed them from the standpoint of clinicoradiologic presentation. Survival rates were assessed and compared with those of 646 resected solitary invasive nonmucinous ADCs. Results: Patients with IMA showed longer disease-free survival (DFS) than did those with nonmucinous ADCs, whereas overall survival (OS) did not differ significantly (p = 0.023 and p = 0.824, respectively). The DFS of patients with IMA was between that of patients with lepidic predominant (low-grade) and acinar/papillary predominant (intermediate-grade) ADC. In terms of OS, the survival curve of IMA was similar to that of acinar/papillary predominant ADC. Multivariate analysis revealed that tumor size (hazard ratio [HR] = 1.370, 95% confidence interval [CI]: 1.141-1.645, p = 0.001) and maximum standardized uptake value (HR = 1.338, 95% CI: 1.160- 1.544, p < 0.001) were independent poor prognostic predictors for DFS. Regarding OS, tumor size (HR = 1.309, 95% CI: 1.092-1.570; p = 0.004) was the only predictor of poor prognosis. Conclusion: Patients with IMA demonstrate a DFS between that of patients with low-grade nonmucinous ADC and that of patients with intermediate-grade nonmucinous ADC and an OS similar to that of patients with intermediate-grade nonmucinous ADC. In IMA, tumor size and maximum standardized uptake value are the factors related to mitigating DFS and tumor size is the only predictor for reduced OS.