Researchers from Yale University have reported that long-term cigarette smoking in women increases the risk of developing follicular lymphoma. The results of this case-controlled study appeared in the December 1 2003 issue of the British Journal of Cancer.
The incidence of non-Hodgkinâ€™s lymphoma (NHL) is increasing in the United States. Some but not all of this increase is due to AIDS-related lymphoma. The causes for the increased incidence of non-AIDS related NHL in the US population is unknown. Previous studies have consistently shown that farmers exposed to insecticides have an increased incidence of NHL, but the identity of specific carcinogens remains obscure.
Exposure to solvents has also been a reproducible association with an increased incidence of NHL. There has also been an unclear association between Epstein-bar virus infection and the incidence of certain lymphomas such as Burketts, Hodgkinâ€™s, and some types of NHL. Recent studies have suggested that the chronic ingestion of aspirin or other non-steroidal anti-inflammatory drugs can lead to an increase in the incidence of NHL.
This is in contrast to a preventative effect for colon cancer and possibly lung and breast cancer with the use of aspirin, other non-steroidals and COX-2 inhibitors. There is currently speculation that the rising incidence of chronic hepatitis C infections is also associated with an increased incidence of NHL but this cannot be confirmed in all studies. Thus, despite all these studies the etiology of most cases of NHL remains elusive.
The authors of the recent Yale study point out that many of the past epidemiology studies have been flawed by not considering sub-types of NHL and usually only distinguish NHL from Hodgkinâ€™s lymphoma. In this study, NHL subtypes were evaluated in 601 patients and smoking histories were compared with 718 control patients without NHL.
The researchers reported that the â€œincreased risk of follicular lymphoma appears to be associated with increased intensity and duration of smoking, and cumulative lifetime exposure to smoking.â€� They reported a 50% increased risk for 16-33 pack-years and an 80% increased risk with 34 pack years or greater. There was no increased risk for the other NHL subtypes.
Comments: This study clearly shows that heavy smoking increases the risk of developing follicular lymphoma and can be added to the list of diseases associated with smoking. However, smoking does not explain the vast majority of NHL cases in this country and around the world. The authors suggestion that epidemiology studies should focus on histological subtypes of NHL is very cogent and could result in new leads on the causes of NHL.