Intensity-modulated radiation therapy (IMRT) was associated with lower rates of severe pneumonitis and cardiac doses compared with 3-dimensional conformal external beam radiation therapy (3D-CRT) in patients with locally advanced non-small cell lung cancer (NSCLC), a study published in the Journal of Clinical Oncology has shown.1
Although the adoption of IMRT for locally advanced NSCLC has increased in recent years, no large study has prospectively compared outcomes after 3D-CRT with those after IMRT in this patient population. Therefore, researchers conducted a secondary analysis of the NRG Oncology clinical trial RTOG 0617, which evaluated overall survival after standard-dose vs high-dose radiotherapy and concurrent chemotherapy with or without cetuximab in stage IIIA and IIIB NSCLC.
Of 482 patients treated in that study, 53% received 3D-CRT and 47% had IMRT. Patients in the IMRT group had larger planning treatment volumes (P =.005), treatment volume/volume of lung ratios (P =.013), and more stage IIIB disease (P =.056).
Results showed that were no significant differences in 2-year overall survival, progression-free survival, local failure, and distant metastasis-free survival between IMRT and 3D-CRT.
However, the researchers found that IMRT was associated with fewer cases of grade 3 or worse pneumonitis (P =.039), which correlated with a 59% reduced odds of developing grade 3 or worse pneumonitis (odds ratio, 0.41; 95% CI, 0.171-0.986; P =.046).
The study further demonstrated that IMRT was associated with lower cardiac doses (P <.05), and after adjusting for confounding variables, analysis showed that the volume of heart receiving 40 Gy of radiation was significantly associated with overall survival (P <.05). In addition, the volume of lung receiving 20 Gy was associated with increased risk for developing grade 3 or worse pneumonitis (P =.026).
Because IMRT produces a lower incidence of severe pneumonitis without compromising efficacy, the findings ultimately support the routine use of IMRT in patients with locally advanced NSCLC.
1. Chun SG, Hu C, Choy H, et al. Impact of intensity-modulated radiation therapy technique for locally advanced non–small-cell lung cancer: a secondary analysis of the NRG Oncology RTOG 0617 randomized clinical trial. J Clin Oncol. 2016 Oct 3. doi: 10.1200/JCO.2016.69.1378. [Epub ahead of print]