Interim Analysis Results of a Phase 2 Trial of Low-Dose Radiation Therapy for Palliation of Diffuse Large B-Cell Lymphoma

Abstract

Results: A total of 1484 patients were identified (372 current, 1014 former, and 98 never smokers). The 5-year incidence of SPLC was 13%, 7%, and 0% for current, former, and never smokers (p Z 0.03 comparing current and never). In the follow-up period, only one never smoker developed a SPLC at 7 years. On MVA, when restricting the analysis to ever smokers with pack-years (PY) as a continuous variable, the risk of SPLC was significantly increased with tobacco exposure with a HR of 1.08 (95% CI Z 1.02-1.16, p Z 0.031), corresponding to an 8% increased risk per 10 PY. For the entire cohort, there were no differences in LC or DM based on smoking status. When grouped as never smokers (nZ 98), former smokers quit > 5 yrs prior to surgery (n Z 493), former smokers quit 5 yrs prior to surgery (nZ 521), and current smokers (nZ 372), OS was significantly worse for current smokers when compared to all other cohorts (p 5 years), and 0.783 (95% CI Z 0.66-0.929, p Z 0.005) for former smokers ( 5 years). There was a trend toward higher post-operative mortality in never smokers as compared to ever smokers (0% vs 3.3%, p Z 0.069). Conclusions: In this, the largest series of its kind, it was demonstrated that increasing tobacco exposure is associated with a higher risk of SPLC. Never smokers have a low incidence of SPLC. This has implications for post-treatment surveillance in this population as well as for patients undergoing stereotactic body radiation therapy. Finally, current smokers are at increased risk of mortality, while former and never smokers have comparable outcomes. Author Disclosure: J.M. Boyle: None. J.P. Chino: None. D. Tandberg: None. K.A. Higgins: None. C.R. Kelsey: None.