Evaluation of Postoperative Radiotherapy in Patients with Non-Small Cell Lung Cancer. A Retrospective Study

Introduction: Surgery remains the most important treatment modality in non-small cell lung cancer. Indications for postoperative radiotherapy in this patient population have been the subject of debate for many years. Currently, patients with metastatic mediastinal lymph nodes (pN2) or with micro- or macroscopically non-radical resection are offered adjuvant radiotherapy in many institutions. The aim of this study was to retrospectively evaluate the results of postoperative radiotherapy in non-small lung cancer patients. Material and methods: Between December 1993 and November 2005, 366 patients underwent radical radiotherapy in the Department of Radiotherapy of Institute of Oncology at Wawelska St. in Warsaw, following surgical procedures. Indications for radiotherapy included non-radical resection in 192 patients, mediastinal lymph node metastases in 174 patients, or a combination of both in 26 persons. Stage I or II was assigned to 96 patients (I—9 pts, 2.4%; II—87 pts, 24%). Stage IIIA disease was present in 252 patients (69%), and stage IIIB in 18 persons (5%). Zubrod performance status 0 was noted in 302 patients (82.5%), score 1 in 54 patients (14.8%), and score 2 in 10 persons (2.7%). The results of treatment were analysed retrospectively. Major end-points in the study were survival and time to local recurrence. The percentage of surviving patients was calculated using the Kaplan-Meier estimator. The prognostic impact of various factors was analysed using multivariate analysis according to the Cox proportional hazard model. Results: One-year survival was reached by 78.02 ± 2% patients in the studied group, with two-year survival in 54.14 ± 2%, and five-year survival in 31.03 ± 2% patients. Two-year local recurrence-free survival was 45.62% ± 4%, and a five-year period free from recurrences was reached by 27.37 ± 4% patients. The probability of survival was significantly better in patients with better performance status, with a median survival of 2.75 years in patients with Zubrod score 0 and 1.67 years in Zubrod 1 + 2. Patients receiving > 50 Gy irradiation had significantly better prognosis; median survival was 4.42 years in the > 50 Gy group and 2.25 years in the ≤ 50 Gy group. Furthermore, local recurrences were less frequent in patients irradiated with > 50 Gy. Patients planned for therapy using the 3D radiotherapy technique did not experience local recurrences; however, most of them received higher radiation doses compared to the others. A significant negative prognostic impact was found for radiation dose ≤ 50 Gy, worse performance status, and older age in univariate analysis. Good performance status (0) was prognostically beneficial. Multivariate analysis confirmed a significant adverse prognostic impact of total radiation dose lower than 50 Gy and older age, with good performance status being an independent good prognostic factor. Conclusions: 1. The efficacy of postoperative radiotherapy depended on radiation dose, patient age, and performance status. Total radiotherapy dose > 50 Gy, younger age, and better performance status significantly correlated with longer survival. 2. Application of the 3D technique resulted in an optimal local control of the disease.