CHICAGO — Proton beam therapy improved OS compared with conventional photon-based therapy in patients with stage II/III non–small cell lung cancer, according to results of a retrospective database analysis presented at the ASCO Annual Meeting.
Further, patients with higher income and education levels and those with government-issued insurance treated at academic centers were the most likely to undergo proton therapy.
“Clinical outcomes in patients with newly diagnosed NSCLC are best in patients with resectable early-stage disease where 5-year OS rates range between 15% and 17%,” Madhusmita Behera, PhD, director or Winship Research Informatics at Winship Cancer Institute at Emory University, said during a presentation. “Photon-based external beam radiation plus concurrent chemotherapy is the current standard of care for patients with unresectable stage III NSCLC.”
Proton beam therapy has emerged as an alternative to conventional photon therapy for many cancer types. Recent data suggest proton therapy has a significant advantage in sparing healthy tissue compared with photon therapy. However, it is not known whether proton therapy improves OS in patients with NSCLC.
Behera and colleagues pooled data from the National Cancer Data Base to assess outcomes and predictors associated with thoracic radiation in 140,383 patients (median age, 68 years; 57% men; 59% white) with stage I to stage IV NSCLC treated between 2001 and 2012. Fifty-nine percent of patients had stage II/III disease.
Of these patients, 140,035 were treated with photon therapy and 348 received proton therapy. Seventy-two percent of patients were treated at metropolitan centers and the other 28% were treated at academic centers.
Researchers conducted logistic regression analyses to determine predictors of proton therapy use.
Results showed proton therapy was less likely among patients treated in community (OR = 0.2; P < 0.001) or comprehensive community centers (OR = 0.32; P < 0.001) compared with academic centers.
Further, patients who underwent proton therapy were more likely to have a higher income and education level. Forty-five percent of patients who received proton therapy were from zip codes with a median income of more than $46,000 — the highest income quartile according to the U.S. Census Bureau.
Results of multivariate analysis indicated that the risk for death was greater with use of photon therapy (HR = 1.46; P < .001).
Among patients with stage II/III disease, a greater proportion of those who received proton therapy achieved 5-year OS (22.3% vs. 15%; P = .01). Patients with stage II/III disease who received photon therapy had worse OS in multivariate (HR = 1.19; P = .06) and univariate (HR = 1.23; P = .02) analyses.
Further, results of a propensity-matched analysis showed more patients achieved 5-year OS with proton therapy vs. photon therapy (23% vs. 14%; P = .02).
Median OS was 11 months with photon therapy vs. 19 months with proton therapy.
The researchers acknowledged limitations of their study, including a potential influence of patient section, small sample size and a lack of toxicity data.
“Our results show that thoracic radiation with proton therapy is associated with favorable survival,” Behera said. “Also, the use of proton therapy was associated with higher education and higher income levels as well as treatment received at an academic center. The ongoing phase 3 randomized trial, NRG Oncology 1308, will hopefully provide us with additional information on the role of proton therapy in stage II/III patients.” – by Jennifer Southall
Behera M, et al. Abstract 8501. Presented at: ASCO Annual Meeting; June 3-7, 2016; Chicago.
Disclosure: Behera reports no relevant financial disclosures. Please see the abstract for a list of all other researchers’ relevant financial disclosures.