Advantages of CyberKnife for inoperable stage I peripheral non-small-cell lung cancer compared to three-dimensional conformal radiotherapy.

This study was conducted to compare the clinical curative effect and acute radiation lung reactions between CyberKnife (CK) and three-dimensional conformal radiotherapy (3DCRT) treatment for inoperable stage I peripheral non-small-cell lung cancer (NSCLC). We retrospectively analyzed 68 patients with inoperable stage I peripheral NSCLC between 2012 and 2013 in our institution. The CK patients were treated with 42-60 Gy in three fractions, while the 3DCRT patients were treated with a total of 60 Gy, at 2 Gy per fraction. The patients were followed up and the clinical outcome was evaluated according to the Response Evaluation Criteria in Solid Tumours. We assessed the presence of acute radiation pneumonitis and pulmonary function status by thoracic scan and pulmonary function tests following CK and 3DCRT treatment. The binary univariate logistic regression analysis demonstrated that treatment method and forced expiratory volume in 1 sec/forced vital capacity (FEV1/FVC) prior to treatment (pre-FEV1/FVC) were the main factors affecting the risk of radiation pneumonitis. The analysis of these factors through multivariate logistic regression method demonstrated that treatment method for grade 1 and 2 [odds ratio (OR)= 7.866 and 11.334, respectively) and pre-FEV1/FVC for grade 1, 2 and 3 (OR = 5.062, 11.498 and 15.042, respectively) were significant factors affecting the risk of radiation pneumonitis (P<0.05). The 68 patients were divided into two subgroups using the threshold of pre-FEV1/FVC selected by the receiver operating characteristic curve. There were significant differences between the 3DCRT and CK treatment in both the pre-FEV1/FVC <68% and ≥68% subgroups for radiation pneumonitis (P=0.023 and 0.002, respectively). There was no statistically significant change in FVC, FEV1 and carbon monoxide diffusion capacity (DCLO) in the CK group, whereas there was a decrease in DCLO in the 3DCRT group. The complete remission rate was 40 vs. 34.2% at 1 year in the CK and 3DCRT groups, respectively. In conclusion, in this cohort of patients with inoperable stage I peripheral NSCLC, CK appears to be a safe and superior alternative to conventionally fractionated radiotherapy.