Postoperative survival and oncologic characteristics of stage IA invasive mucinous adenocarcinoma

The prognosis of invasive mucinous adenocarcinoma has not been well investigated because of its rarity, especially with regard to early-stage disease. This study aimed to compare the prognosis of early-stage invasive mucinous adenocarcinoma with that of non-mucinous adenocarcinoma and to clarify oncologic characteristics of early-stage invasive mucinous adenocarcinoma.

Patients with pathological stage IA lung adenocarcinoma, excluding pT1mi tumors, who underwent surgery at three institutions were retrospectively examined. Overall survival and recurrence-free survival were compared between patients with invasive mucinous adenocarcinoma and non-mucinous adenocarcinoma. Propensity score matching was applied to reduce baseline imbalances.

Among the 1228 patients, 1128 had non-mucinous adenocarcinoma and 100 had invasive mucinous adenocarcinoma. Before matching, invasive mucinous adenocarcinoma was significantly associated with smaller pathological whole tumor size, larger pathological invasive tumor size and a lower frequency of lymphovascular invasion. The 5-year overall survival rates were 92.5% and 92.7%, and the 5-year recurrence-free survival rates were 87.5% and 92.3% in patients with invasive mucinous and non-mucinous adenocarcinoma, respectively. Baseline covariates including pathological tumor size and stage were generally balanced after matching. The 5-year overall survival rates were 90.4% and 92.7%, and the 5-year recurrence-free survival rates were 83.7% and 93.3%, respectively, with no significant differences in survival curves between groups.

The postoperative prognosis of patients with pathological stage IA invasive mucinous adenocarcinoma was comparable to that of patients with non-mucinous adenocarcinoma. These findings suggest that mucinous histology alone should not be considered an adverse prognostic factor in early-stage disease.