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Smoking increases risk for death, disease progression in CML
Patients with chronic myeloid leukemia who smoked faced a higher risk for disease progression and death than nonsmokers, according to researchers in Germany.
“As in many other types of cancer, tobacco smoking is suspected to be a risk factor for the development of chronic myeloid leukemia,” Michael Lauseker, PhD, of the Institute for Medical Information Sciences, Biometry and Epidemiology at Ludwig-Maximilians University, Munich, and colleagues wrote. “However, to the best of our knowledge, it is currently not clear whether smoking is also an unfavorable prognostic factor.”
The researchers used a Cox model to analyze the effects of smoking on 1,536 patients with CML who participated in the German CML Study IV. All patients had been categorized as either smokers or nonsmokers at the start of the trial, and only those who were currently smoking were considered smokers.
At a median follow-up of 7 years, Lauseker and colleagues reported a total of 163 deaths. Another 95 patients experiencing disease progression.
Of the total cohort, 261 patients (20%) were current smokers. Smoking was more common among men (24%) than in women (13%), and patients who smoked tended to have lower levels of education, with 13% of patients holding an advanced degree compared with 25% of nonsmokers (P < .001).
Nonsmokers had a higher 8-year survival probability than smokers (87% vs. 83%).
Smokers’ risk for death was 2.08 times higher than that of nonsmokers, and their risk of cause-specific disease progression was 2.11 times greater.
Smokers also experienced a higher 8-year cumulative incidence of disease progression than nonsmokers (12% vs. 7%).
“To our knowledge, the current study is the first to demonstrate the unfavorable effects of smoking in patients with CML in a confirmatory way in the tyrosine kinase inhibitor era, based on a large data set with adequate follow-up,” the researchers wrote. “Therefore, the results of the current study suggest that patients with CML, especially those aged younger than 60 years, should receive adequate encouragement and support to quit smoking.” – by Andy Polhamus
Disclosure: Lauseker reports no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.
Perspective
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Tyrosine kinase inhibitors virtually paved the way for a new approach to the treatment of hematological malignancy. These agents continue to have a profound impact on the outlook for patients afflicted with chronic myeloid leukemia (CML).
Historically, chemotherapy served little long-term utility in this disease state. Although bone marrow or peripheral blood stem cell transplantation previously had been the only known means of long-term survival, such therapy was fraught with complication in the era just prior to tyrosine kinase inhibitors.
These drugs have indeed altered the natural history of the disease, with most patients tolerating therapy while achieving deep molecular remissions. With such a large swing in outcomes in a relatively short period of time, neither clinicians nor patients should minimize the seriousness of the disease or the role of lifestyle modifications that are already known to impact health.
The study by Lauseker and colleagues demonstrates that exciting changes in therapy in this era do not neutralize the adverse health risks associated with tobacco smoking in patients with CML. Of particular importance is the finding that the status of the disease itself can be negatively impacted by smoking as an independent variable, particularly in younger individuals.
Although the development of resistance to therapy by virtue of emerging mutations could not be assessed in this study, there appears to be a negative impact on disease biology and outcomes as a result of tobacco smoking. These findings highlight the responsibility of providers to encourage smoking cessation in this population, as well as the responsibility of patients to make every effort to quit.
Although it is not yet known if quitting after diagnosis will result in similar outcomes to those of nonsmokers, data are intriguing enough to encourage this active dialogue. This study further supports efforts to discourage the start of smoking habits in all populations.