Risk factor analysis for predicting radiation pneumonitis in extensive stage small cell lung cancer patients receiving IMRT thoracic radiotherapy

Abstract

Objective To evaluate the clinical factors and dose-volume histogram-based factors as predictors of radiation pneumonitis (RP) in extensive-stage small cell lung cancer (ES-SCLC) patients treated with thoracic IMRT after chemotherapy. Methods Medical records of 130 ES-SCLC patients irradiated in our institution between 2007 and 2012 were retrospectively reviewed. Most patients received an initial chemotherapy regimen of combined carboplatin and etoposide or with cisplatin combined with etoposide. The median thoracic radiation dose was 55.3 Gy (32-67 Gy) with 1.8-2.3 Gy per fraction. RP was graded according to Common Terminology Criteria for Adverse Events version 4.0, and RP at a grade of ≥Ⅱ is considered as a complication. Univariate and multivariate analyses were conducted to identify the predictive factors. Results Median follow-up period was 37 months (range: 4-66 months). A total of 37 patients (28.5%) showed an RP grade of ≥Ⅱ. The univariate analysis revealed that in the entire population, age and many dosimetric parameters (V5, V10, V20, V30, mean lung dose, and total lung volume)were significantly associated with RP. By contrast, multivariate analysis showed that only V5 was significantly associated with RP. Conclusions In this study, a number of clinical and dosimetric factors are associated with a high risk of RP. However, V5 was the only significant factor associated with this condition. Multiple clinical and dosimetric factors should be considered in IMRT planning for ES-SCLC patients receiving thoracic radiotherapy after chemotherapy. It is proposed that V5 should be kept low to reduce the development of RP in ES-SCLC patients after chemotherapy. Key words: Carcinoma, small cell; Radiotherapy; Radiation pneumonitis; Intensity-modulated radiation therapy