ASTRO 2015: Intensity-Modulated Radiotherapy Causes Less Inflammation Than 3D Conformal Radiotherapy in Lung Cancer Patients
Patients with stage III non–small cell lung cancer (NSCLC) who receive intensity-modulated radiation therapy (IMRT) have 44% fewer cases of severe pneumonitis and improved likelihood of completing consolidative chemotherapy after radiation, compared to patients who receive three-dimensional conformal radiation therapy (3D CRT), according to research presented by Chun et al on October 18 at the American Society for Radiation Oncology’s (ASTRO’s) 57th Annual Meeting in San Antonio, Texas.
The standard of care for patients with locally advanced lung cancer is concurrent chemotherapy with radiation therapy. Two different types of radiation therapy are typically used to treat these patients: 3D CRT and IMRT. Although IMRT is a more advanced and more expensive form of radiation therapy, it can target treatment to lung tumors while minimizing radiation exposure of sensitive organs, like the lungs and heart, from high radiation doses.
Study Details
This study is a secondary analysis of the data compiled from NRG/RTOG 0617 to compare the use of IMRT and 3D CRT in patients with lung cancer. NRG/RTOG 0617 was a large, multi-institutional, phase III, randomized clinical trial of patients with locally advanced NSCLC conducted from 2007 to 2011. The original study compared a high-dose of 74 Gy to a standard dose of 60 Gy. All patients received concurrent chemotherapy consisting of carboplatin/paclitaxel and were randomly assigned to be treated with or without cetuximab (Erbitux).
Of the 482 patients treated with radiation therapy, 47% were treated with IMRT and 53% were treated with 3D CRT. Because the original trial design was not randomized for radiation technique, the IMRT group had larger and more advanced-stage tumors. Data indicated that 38.6% of the IMRT group had stage IIIB tumors, compared to 30.3% of the 3D CRT group.
Study Findings
The study results showed that although the IMRT patients had more advanced tumors, they had a lower occurrence of severe pneumonitis (for this study, this was defined as lung inflammation that required oxygen, steroids, or mechanical ventilation; and/or led to death) than patients who had been treated with 3D CRT. Data indicated that 3.5% of IMRT patients had severe pneumonitis, compared to 7.9% of the 3D CRT patients (P = .046). IMRT remained associated with less severe pneumonitis in multivariate analysis (hazard ratio [HR] = 0.44, P = .0653), and was particularly pronounced in large tumors that were bigger than the median size of 460 mL (HR = 0.22, P = .02).
IMRT was also associated with significantly lower doses of radiation delivered to the heart, which were highly associated with patient survival. Additionally, patients treated with IMRT were more likely to complete high-dose consolidative chemotherapy than patients treated with 3D CRT (37% vs 29%, P = .051).
“We looked at one of the largest clinical trials ever done for locally advanced NSCLC, and found that the most important factors associated with severe pneumonitis were IMRT technique and the lung V20 [ie, the percentage of lung volume (with subtraction of the volume involved by lung cancer) that receives radiation doses of 20 Gy or more]. The low-dose bath … was not associated with any toxicity outcome. These findings have the potential to fundamentally change the way we deliver radiation therapy for locally advanced lung cancer,” said Stephen Chun, MD, Fellow in the Department of Radiation Oncology at The University of Texas MD Anderson Cancer Center.
“By reducing severe life-threatening pneumonitis, IMRT has the potential to improve patients’ quality of life, reduce hospital/intensive care unit admissions, and decrease supplemental oxygen use. In our study, it seemed that IMRT might also facilitate patients being able to tolerate higher doses of consolidative chemotherapy, which are standard after radiation,” he added.
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