Impact of Smoking Behavior on Survival Following Allogeneic Hematopoietic Stem Cell Transplantation - Smoking Cessation Matters.

INTRODUCTION: There are only a few data on the impact of smoking and smoking cessation on the outcome of patients treated with allogeneic hematopoietic stem cell transplantation, a well-established therapy for hematologic malignancies.

METHODS: In a retrospective cohort study design we examined the impact of smoking and smoking cessation on survival among 309 eligible consecutive adults who underwent allogeneic hematopoietic stem cell transplantation using reduced-intensity (n = 179) or myeloablative (n = 130) conditioning between 1999 and 2018.

RESULTS: Smoking and was independently associated with increased mortality with a five-year overall survival of 25% in current smokers versus 53% in never smokers versus 48% in past smokers. Never smokers lived significantly longer (HR: 2.00, 95%CI: 1.19-3.35, p = .008) and had a better event-free survival (HR: 2.11, 95%CI: 1.27-3.49, p = .004) than current smokers. In the long run, never smokers also lived significantly longer than past smokers (HR: 1.45, 95%CI: 1.16-1.81, p = .001). Patients who quit smoking before allogeneic hematopoietic stem cell transplantation showed a tendency towards increased survival compared to those who continued smoking (HR: 1.53, 95%CI: 0.95-2.45, p = .078). In relation to life-time cigarette dose smokers with low-dose (1-10 pack-years) cigarette consumption lived significantly longer (HR: 1.60, 95%CI: 1.03-2.50, p = .037) and had a better event-free survival (HR: 1.66, 95%CI: 1.07-2.58, p = .025) than patients with high-dose (≥10 pack-years) cigarette consumption.

CONCLUSIONS: In allogeneic hematopoietic stem cell transplantation for hematologic malignancies, smoking history per se, lifetime cigarette dose, and continued smoking, were significantly associated with increased all-cause mortality and reduced event-free survival.

IMPLICATIONS: Continued and past smoking represent established risk factors for malignant and non-malignant diseases, however, they are also a strong risk factor for a poor outcome after allogeneic hematopoietic stem cell transplantation for hematologic diseases. Our study shows that the hazard ratio for death after such transplantation is doubled if patients continue smoking and even if they have quit smoking, their risk remains significantly elevated. This suggests that the smoking history provides important predictive factors for the outcome of allogeneic hematopoietic stem cell transplantation and that smoking cessation should be implemented in the treatment of hematologic diseases as early as possible.