Smoking Worsens Prognosis for Patients With CML

Smoking is linked to mortality and to disease progression among patients with chronic myeloid leukemia (CML), according to a new study. The results suggest that smoking could affect disease biology in this malignancy.

Smoking is suspected to be a risk factor for development of CML, but its status as a prognostic risk factor is unclear. “The few analyses regarding this topic published to date were performed long ago in the era before tyrosine kinase inhibitors, or within the context of stem cell transplantation,” wrote study authors led by Michael Lauseker, PhD, of Ludwig-Maximilians University in Munich.

This study involved 1,536 patients from the German CML Study IV; of those, 1,326 had smoking status available for analysis. Over a median observation time of 7.0 years, there were 163 deaths, and 95 patients experienced disease progression to accelerated phase or blast crisis. Results of the analysis were published in Cancer.

A total of 261 patients (20%) were smokers (only current smokers at diagnosis were considered smokers). The 8-year overall survival rate was 87% for nonsmokers, and 83% for smokers. On a multivariate analysis, smoking had a significant effect on mortality, with a hazard ratio (HR) of 2.08 (95% CI, 1.4–3.1; P < .001), which was stronger than that seen on a univariate analysis. Other factors significantly associated with mortality included increasing age and comorbidities, as well as several others.

The effect of smoking appeared to be dependent on age, based on a sensitivity analysis. For example, a 16-year-old smoker had an HR for mortality of 8.47 (95% CI, 2.8–25.8; P < .001) compared with a 16-year-old nonsmoking patient; an 80-year-old smoker, in contrast, had no increased risk compared with a nonsmoker of the same age.

Disease progression was also worse in smokers. The 8-year cumulative incidence rate of progression was 7% for nonsmokers, compared with 12% in smokers, for a multivariate HR of 2.11 (95% CI, 1.35–3.31; P = .001). Molecular response rates were no different between smokers and nonsmokers.

“When determining the prognosis of a patient with CML, smoking should be considered to be an important prognostic factor,” the authors concluded. “Patients with CML, especially those aged < 60 years, should receive adequate encouragement and support to quit smoking.”