Smoking May Increase Risk for Developing Myeloproliferative Neoplasms

Smoking may be a risk factor in the development of myeloproliferative neoplasms (MPNs), according to Danish study results published in Cancer Medicine.

“It has been highlighted that smokers and patients with MPNs share features of an increased inflammatory burden, including, upregulation of important molecular pathways and transcriptions factors,” the researchers wrote. “These shared factors, all of which are vigorously amplified, are known to be involved in tumorigenesis (or the formation of tumors) and cancer progression.”

“Owing to these similarities and the model of chronic inflammation and its role in the clonal evolution and progression of MPNs, it is tempting to suggest smoking as one of several potent inflammatory stimuli potentially triggering and driving the MPN‐clone,” they added.

However, former studies that have attempted to confirm this theory have mainly been carried out in female cohorts or their definition of MPNs were not consistent, according to the study. Therefore, the researchers conducted follow-up from the Danish Health Examination Survey cohort to validate and substantiate whether daily smokers or occasional/ex‐smokers had an increased risk of developing MPNs compared with never‐smokers.

In the survey, 76,484 Danish citizens filled out two internet‐based questionnaires: a basic questionnaire containing questions on sociodemographic and health behavior including smoking status, self‐reported health and living conditions; and a supplementary questionnaire concerning diet.

Smoking status was reported as never, daily, current but not daily — which was reported in categories of at least once per week but not daily, once per month or rarer than once per month – and former smoking. Participants were then categorized as never‐smokers, occasional/ex-smokers or daily smokers.

Overall, the researchers found 70 survey respondents who developed MPNs during the period of follow‐up, of which 41 were women and 29 were men at a median age of 63 years at MPN diagnosis. Patients were diagnosed with essential thrombocythemia (23 cases), polycythemia vera (17 cases), myelofibrosis (10 cases) and unclassifiable MPNs (27 cases).

Of the 70 individuals, 20 were never-smokers, 35 were occasional/ex-smokers and 15 were daily smokers.

The risk for developing MPNs was 2.5 times higher for those who reported to be daily smokers, and 1.9 times more likely for those who were occasional/ex-smokers. When broken down by MPN subtype, daily smokers and occasional/ex-smokers were 1.8 and 1.9 times more likely, respectively, to develop essential thrombocytosis; 1.7 and 1.5 times more likely to develop polycythemia vera; 4.3 and 0.8 times more likely to develop myelofibrosis; and 6.2 and 0.9 times more likely to develop unclassifiable MPNs.

Among participants who smoked, those with an intake of more than 15 grams per day were 3.4 times more likely to develop any MPN compared with those who smoked less and were only 2.1 times as likely to develop the malignancy.

The researchers advised for caution when interpreting these results, “as they are likely affected by the low number of cases because of a relatively short follow‐up period combined with the fact that MPNs are rare diseases,” adding, however, that they do support the growing evidence that suggests smoking may be a risk factor in the development of MPNs.