Purpose: The correlations between histological, clinical features and prognosis of stage I invasive mucinous adenocarcinoma (IMA) have not been thoroughly studied for its rare incidence. This study aimed to compare the prognosis among IMA with different percentage of mucinous component and the effect of adjuvant chemotherapy on IMA patients.
Methods: A total of 145 stage I IMA and 3536 invasive nonmucinous adenocarcinoma patients with R0 resection were included. Based on the percentage of mucinous pattern presented in tumor, IMA were classified into two subgroups: pure mucinous (>90 % invasive mucinous pattern) and mixed mucinous/nonmucinous (≥10 % of each histologic component). Invasive nonmucinous adenocarcinomas were classified into three subgroups: lepidic (LEP), acinar/papillary (ACN/PAP) and solid/micropapillary (SOL/MIP). Disease-free survival (DFS) and overall survival (OS) were assessed and compared among IMA and invasive nonmucinous patients.
Results: For IMA patients, DFS (p = 0.003) was worse for mixed mucinous/nonmucinous compared with pure mucinous subgroup, OS (p = 0.514) was not prognostically different between two groups. There were no significant difference for DFS (p = 0.428) and OS (p = 0.232) between IMA and invasive nonmucinous adenocarcinoma. However, statistical significance were seen for DFS (p < 0.001) and OS (p < 0.001) between 5 major histological subgroups: LEP and pure IMA showed excellent prognosis, mixed mucinous/nonmucinous IMA and SOL/MIP subtypes presented the worst prognosis. No significant survival benefit from adjuvant chemotherapy for IMA patients.
Conclusions: Mixed mucinous/nonmucinous IMA had a worse DFS compared with pure mucinous. Early stage IMA could not benefit from adjuvant chemotherapy.
Keywords: Adjuvant chemotherapy; Classification; Invasive mucinous adenocarcinoma; NSCLC; Stage I.