Effects of smoking on outcomes of hematopoietic cell transplantation: a systemic review and future directions

Hematopoietic cell transplantation (HCT) survivors are at risk of increased mortality compared to the general population. Smoking by HCT survivors has been reported to impact a variety of health outcomes, resulting in an increased risk for infections, cardio-pulmonary diseases, and cancer. The purpose of our study was to conduct a systematic literature search to determine the relationship between tobacco smoking pre-HCT and post-HCT outcomes. We conducted an electronic literature search from all languages from multiple peer-reviewed databases of studies that evaluated the effects of tobacco smoking prior to HCT on clinical outcomes. Data were extracted from the studies according to a strict selection criterion. Due to differences in primary endpoint and different populations evaluated in different studies, a meta-analysis was not possible, and a descriptive quantitative analysis is provided. Out of the 447 publications fulfilling the selection criteria for the electronic search, 17 articles were included in the final sample. The studies varied in terms of study design, patient characteristics, and HCT type. Considerable variability in definition of smoking was observed. We found that smoking pre-HCT was associated with a higher incidence of cardiovascular diseases, new infections, pulmonary complications, and cancers in comparison to non-smokers. Moreover, smoking pre-HCT was significantly associated with increased risks of both relapse and non-relapse mortality, and inversely related to median overall survival. Smoking adversely affects mortality in all HCT survivors by increasing the risks of both malignant and non-malignant complications. Thus, guidelines are urgently needed to formulate lifestyle factor modifications for HCT survivors focusing on smoking cessation strategies and abstinence maintenance in former smokers. Given the strength of these findings, guidelines should include systematic definitions of smoking for use in clinical trials as well as in standardized data reporting.