Five-year results of a single-institution study show that proton beam radiotherapy given concurrently with chemotherapy offers promising clinical outcomes with good toxicity results compared with historical data.
Five-year results of a single-institution study show that proton beam radiotherapy (PBT) given concurrently with chemotherapy offers promising clinical outcomes with good toxicity results compared with historical data on photon therapy for patients with locally advanced, unresectable non–small-cell lung cancer (NSCLC).
“The use of PBT is an attractive option with which to reduce toxic effects of concurrent chemoradiotherapy,” wrote study authors led by Joe Y. Chang, MD, PhD, of the University of Texas MD Anderson Cancer Center in Houston. “Implications for lung cancer therapy include the ability to safely deliver the desired dose while maintaining low doses to cardiopulmonary structures, which may affect toxic effects, functional status, quality of life, and/or survival.”
The new study included 64 patients with unresectable NSCLC. All patients received carboplatin/paclitaxel concurrently with passively scattered PBT 74 Gy. The study had a median follow-up of 27.3 months for all patients, and 79.6 months for survivors. The results were published online ahead of print in JAMA Oncology.
The median overall survival was 26.5 months; the 5-year overall survival rate was 29%. The median progression-free survival in the study was 12.9 months, and the five-year progression-free survival rate was 22%.
A total of 39 patients experienced a relapse, and the dominant mode of treatment failure was distant relapse; this occurred in 48% of patients, and accounted for 62% of all recurrences. The authors noted that nearly all the distant treatment failures were not accompanied by local or regional relapse. Local and regional recurrences were seen in 10 (16%) and 9 (14%) patients, respectively.
With regard to acute toxicity, five patients (8%) experienced grade 3 esophagitis, and 18 others (28%) had grade 2 esophagitis. There was only case of grade 2 pneumonitis (2%), and no cases of this toxicity at grade 3 or 4. Cardiac arrhythmia and ischemia both occurred in two patients (3%).
Late grade 2 esophagitis occurred in three patients (5%), and late grade 3 and 4 esophagitis occurred in one patient each (2%). For late pneumonitis, there were ten grade 2 cases (16%) and eight grade 3 cases (12%).
“We demonstrate that concurrent PBT and chemotherapy was safe and efficacious from the long-term perspective, and hence justifies further prospective investigation,” the authors concluded.
In an accompanying editorial, Charles R. Thomas, Jr, MD, of Oregon Health Sciences University in Portland, wrote that prospective trials of PBT have lagged even as the number of centers offering this therapy has increased. “This is unfortunate and has delayed the generation of crucial evidence-based recommendations for use of this component of the anticancer toolbox.” He called the new study an important step, and noted an ongoing phase III trial that will compare photon therapy to proton therapy in lung cancer patients.