SAN ANTONIO, TX—An analysis of an international, cooperative-led trial of patients with locally advanced non-small cell lung cancer (NSCLC) has shown that those who received intensity modulated radiation therapy (IMRT) had less severe lung toxicity and were able to better tolerate their chemotherapy, compared with patients who received 3-dimensional conformal radiation therapy (3-D CRT). These results were presented the 2015 American Society for Radiation Oncology (ASTRO) Annual Meeting.
According to the American Cancer Society, in the United States, 221 200 cases of lung cancer will be diagnosed in 2015 and 158 040 will die from the disease, which makes it the deadliest of all cancers. Approximately one-third of all lung cancers are diagnosed when the cancer is locally advanced, said lead author Stephen Chun, MD, a fellow in Radiation Oncology at The University of Texas MD Anderson Cancer Center. The standard of care for locally advanced lung cancer is concurrent chemotherapy and radiation, with most patients undergoing either 3-D CRT or IMRT.
For decades, 3-D CRT has been the standard of care for the treatment of lung cancer. The technique shapes radiation beams aimed in straight lines to match the shape of the tumor. In contrast, IMRT is a newer, more-advanced technique that sculpts and molds radiation beams to tumor targets, using substantially more complex radiation beam arrangements than 3D-CRT. In turn, IMRT can spare more normal tissue than 3D-CRT with high doses of radiation, explained Chun.
“IMRT was developed more than a decade ago and because it’s been shown to reduce toxicity, it has been accepted to treat prostate, brain, and head and neck cancers,” said Chun. “There have been a number of smaller studies, including research led by MD Anderson, looking at IMRT and lung cancer. This is the first analysis of a prospective clinical trial to show a reduction of toxicity associated with IMRT in locally advanced lung cancer. It could lead to a major change in the way radiation therapy is delivered for the disease.
“The data from our study makes a strong argument that we should routinely consider use of IMRT in locally advanced lung cancer,” Chun continued.
This study is a secondary analysis of data collected from the NRG/RTOG 0617, a large, multicenter phase III randomized trial of patients with locally advanced NSCLC. The study originally enrolled patients from 2007 to 2011 and compared a high dose of 74 Gy to the standard dose of 60 Gy. All participants underwent concurrent chemotherapy (carboplatin/paclitaxel with or without cetuximab) and either 3-D CRT or IMRT. In the study, NRG/RTOG 0617, 482 patients were treated with radiation: 53% with IMRT and 47% with 3-D CRT.
Study findings showed 44% fewer cases of severe pneumonitis (defined by the researchers as lung inflammation that required oxygen, steroids, or mechanical ventilation, and/or led to death) in patients who underwent IMRT, despite having larger tumors—3.5% of patients vs 7.9% of patients in the 3-D CRT group. Although the benefit of IMRT was seen with all tumor sizes, the reduction of severe pneumonitis was more pronounced with the larger tumors, explained Chun.
In addition, 37% of those who received IMRT were more likely to complete consolidative chemotherapy, compared with 29% of those treated with 3D-CRT. High-dose chemotherapy after completing chemotherapy with radiation is considered to be standard for locally advanced lung cancer.