SAN ANTONIO – Patients with stage III non–small-cell lung cancer undergoing chemoradiotherapy had less lung inflammation if they were treated with intensity-modulated radiation therapy (IMRT) than three-dimensional conformational radiation therapy (3D-CRT) in a secondary analysis of data from the NRG Oncology/Radiation Therapy Oncology Group (RTOG) 0617 trial.
A 44% reduction in grade 3 or higher pneumonitis cases was observed in the analysis, at 4.5% for IMRT and 8% for 3D-CRT, respectively (P = .046), Dr. Stephen Chun of the MD Anderson Cancer Center, Houston, reported at the annual scientific meeting of the American Society for Radiation Oncology.
Courtesy ASTRO/Adam Donohue
Dr. Stephen Chun
RTOG 0617 was one of the largest studies to look at chemoradiation in patients with locally advanced non–small-cell lung cancer, Dr. Chun explained in an interview. This phase III study examined whether there was any advantage of using high-dose (74-Gray) over standard dose (60-Gray) radiation therapy in combination with chemotherapy consisting of carboplatin and paclitaxel with or without additional cetuximab.
How the radiation therapy was delivered was left to the discretion of the treating physicians participating in the multi-institutional trial, and so the aim of the secondary analysis was to see if there was any difference in outcomes between patients who received IMRT versus those who received 3D-CRT.
“Our main hypothesis was that by using highly complex modulated beam arrangements, we would improve oncologic outcomes, whether that be toxicity or tumor control; we looked at all sorts of outcomes,” Dr. Chun said.
“We defined severe or grade 3+ pneumonitis as that requiring high steroids, oxygen, hospital admission, a ventilator, or death,” he said. “So we were really dealing with the most serious types of pneumonitis.”
Among the 482 patients studied in the analysis, 47% had received IMRT, and 53% had received 3D-RT. During his presentation, Dr. Chun noted that the “deck was stacked against IMRT” at baseline, with significantly more patients with stage IIIB (39% vs. 30%) and smaller mean planned target volumes (PTV, 427 mL vs. 486 mL) and a lower PTV/lung ratio (0.13 vs. 0.15) in the IMRT versus 3D-RT groups.
Despite having less favorable tumors at the outset, patients in the IMRT arm did just as well as those in the conventional radiotherapy group in terms of local tumor control. At 2 years, local control was 30.8% and 37.1% (P = .50), respectively.
There was no statistical difference in 2-year overall (53.2% vs. 49.4%, P = .597), progression-free (25.2% vs. 27.0%, P = .595), or distant metastasis-free survival (45.9% vs. 49.6%, P = .66).
IMRT was associated with more consolidative chemotherapy (37.3% vs. 29.1%, P less than .05), and significantly lower doses of radiation were delivered to the heart, which may confer survival and further toxicity benefits in the future with longer follow-up, Dr. Chun suggested. The potential ramifications of the pneumonitis finding are currently such that they could drastically decrease medical and associated hospitalization costs, he added.
“For the past decade or so, IMRT has been accepted for disease sites like the head and neck, the prostate, the brain, and other sites because of potential toxicity benefits. With what we are seeing here, we believe that these findings support more routine use of IMRT for this population and a similar leap in lung cancer,” Dr. Chun said.