Postoperative radiotherapy for incompletely resected non-small cell lung cancer: clinical outcomes and prognostic value of the histological subtype.

The purpose of this study was to evaluate the efficacy and toxicity of the postoperative radiotherapy in patients with incompletely resected NSCLC, and to investigate whether the histological subtype is a prognostic factor. Forty-one incompletely resected NSCLC patients who underwent postoperative radiotherapy were retrospectively analyzed. The microscopic residual tumor (R1 group) was recognized in 23 patients, and the macroscopic residual tumor (R2 group) in 18. The postoperative pathological stages were I (n = 3), II (n = 8), IIIA (n = 17), and IIIB (n = 13). The histology included squamous cell carcinoma (n = 23), adenocarcinoma (n = 14) or other types (n = 4). The first site of disease progression was distant metastases alone for 3 (13%) of 23 with squamous cell carcinoma, and for 9 (64%) of 14 with adenocarcinoma (p < 0.01). The 5-year overall, local control, disease-free, and distant metastasis-free survival rates were 56%, 63%, 37% and 49%. Univariate analyses showed that squamous cell carcinoma histology, N0-1 stage and the R1 group were significant predictors for better disease-free and distant metastasis-free survival. Multivariate showed that squamous cell carcinoma and N0-1 stage were significant predictors for better distant metastasis-free survival. Toxicity was generally mild; Grade 3 toxicities occurred in 3 patients (neutropenia, radiation pneumonia and esophageal stenosis), and no acute and late toxicities of Grade 4 to 5 were observed. In conclusion, postoperative radiotherapy for incompletely resected NSCLC could achieve a relatively high local control rate without severe toxicity. However, different treatment strategies for non-squamous cell carcinoma should be considered, because of the higher risk for the distant metastases.