Results from a worldwide collaborative clinical trial in patients with locally advanced non-small cell lung cancer (NSCLC) revealed that those treated with intensity modulated radiation therapy (IMRT) had lower serious lung toxicity and an improved chemotherapy tolerance compared to those given 3-dimensional conformal radiation therapy (3D-CRT).
The results were presented recently at the 57th Annual Meeting of the American Society for Radiation Oncology (ASTRO) by Stephen Chun, MD, fellow, Radiation Oncology at The University of Texas MD Anderson Cancer Center.
According to Dr. Chun, approximately one-third of all lung cancers are diagnosed when the cancer is already locally advanced, and typical treatment includes concurrent chemotherapy and radiation, either IMRT or 3D-CRT. In recent decades, however, 3D-CRT, a technique that involves a complex process of creating individualized 3-D digital data sets of patients’ tumors and normal adjacent anatomy, has been standard care for patients with lung cancer. The data sets are used to generate 3-D computer images and to develop complex plans to deliver highly “conformed” (focused) radiation to spare normal adjacent tissue. Because higher doses of radiation can be delivered to cancer cells while significantly reducing the amount of radiation received by surrounding healthy tissues, the technique can increase the rate of tumor control while decreasing side effects.
In contrast, IMRT — a newer technique — uses advanced software to plan a precise dose of radiation, based on tumor size, shape, and location. A computer-controlled device called a linear accelerator delivers radiation in sculpted doses that match the 3-D geometrical shape of the tumor, including concave and complex shapes. More advanced, IMRT may be a treatment option for patients who have reached the maximum allowable dose of conventional radiation therapy and have a recurrent tumor in the treated area.
As Dr. Chun explained in a news release, IMRT can spare more normal tissue than 3D-CRT with high doses of radiation. “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 & neck cancers. There have been a number of smaller studies, including research led by MD Anderson, looking at IMRT and lung cancer. This the first analysis of a prospective clinical trial to show a reduction of toxicity associated with IMRT in locally advanced lung cancer and could lead to a major change in the way radiation therapy is delivered for the disease.”
He added, “The data from our study makes a strong argument that we should routinely consider use of IMRT in locally advanced lung cancer.”
The results presented at ASTRO derived from a secondary analysis of data gathered from NRG/RTOG 0617, a large, multi-center Phase 3 randomized clinical trial of patients with a diagnosis of locally advanced NSCLC. The clinical trial initially enrolled patients from 2007 trough 2011 and compared high radiation doses of 74 Gy with a typical 60 Gy dose. All patients received treatment with concurrent chemotherapy (carboplatin/paclitaxel, with or without cetuximab) and with either IMRT or 3D-CRT. In the NRG/RTOG 0617 trial, a total of 482 patients received treatment with radiation (47% with 3D-CRT and 53% with IMRT).
The results revealed there were 44% fewer cases of patients with severe pneumonitis (lung inflammation requiring oxygen, steroids or mechanical ventilation) in the group treated with IMRT. Moreover, IMRT was found to be beneficial in all tumor sizes. Patients treated with IMRT were also more likely to finish consolidative chemotherapy.
“It’s been unclear what the consequences of that low dose bath are. What we’ve seen in this study is that indicators of the low dose bath that’s increased by IMRT had no association with any severe toxicity outcome. This finding suggests that we should be optimizing radiation treatment by the high and intermediate dose region, and not the low dose region,” Dr. Chun explained, adding that even though IMRT is more costly and time-consuming, these results revealed an important reduction in serious toxicities. As such, it may lower the number patients admitted in the hospital and improve the quality of life for those with this severe disease.
