Prognostic value of postoperative radiotherapy for locally advanced pulmonary adenocarcinoma with micropapillary pattern

Objective: To investigate the prognostic significance of postoperative radiotherapy (PORT) for locally advanced pulmonary adenocarcinoma with micropapillary pattern(MPPAC). Methods: A total of 45 completely resected pN_2-3 cases that occured from January 2012 to December 2014 at Tianjin Medical University Cancer Hospital were retrospectively analyzed. All of them were diagnosed with MPPAC by pathological diagnosis. Based on whether receiving PORT, patients were divided into radiotherapy and non-radiotherapy groups. General characteristics, overall survival and disease-free survival characteristics of the two groups were compared, respectively. Results: The median overall survival (OS) of patients was 19.8 months, 1-year and 2-year overall survival rate was 79.4% and 30.3%, respectively. The median disease free survival (DFS) of patients was 13 months, 1-year and 2-year, and the disease free survival rate was 59.3% and 28.9%, respectively. The radiotherapy and non-radiotherapy groups exhibited median OS of 22.3 and 11.4 months, respectively(χ² = 13.329, P < 0.05), and corresponding DFS of 16.2 and 10.4 months(χ² = 7.972, P < 0.05). The epidermal growth factor receptor gene (EGFR) mutation rate of patients was 57.14%(20/35), In the subgroup analysis, for patients with EGFR mutation, the radiotherapy and non-radiotherapy groups showed median OS of 25.6 and 18.4 months, respectively(χ² = 9.268, P < 0.05), and corresponding DFS of 21.6 and 12.6 months(P > 0.05). For patients with wild-type EGFR, the radiotherapy and non-radiotherapy groups showed median OS of 21.8 and 10.6 months, respectively(χ² = 9.595, P < 0.05), and corresponding DFS of 15.2 and 6.6 months(χ² = 4.538, P < 0.05). Conclusions: PORT could improve survival of patients with pN_2-3 MPPAC. For patients with locally advanced MPPAC after curative resection, PORT is still an integral part of treatment. (authors)