Scientists have uncovered an intriguing relationship between the risk for Kaposi's sarcoma (KS), smoking, and the use of highly active antiretroviral therapy (HAART).
Data for 2736 HIV-positive men showed that both current smoking and use of HAART independently and significantly reduced the risk for developing KS, with hazard ratios (HRs) of 0.56 and 0.27, respectively, after adjusting for age, race/ethnicity, employment status, education, income, and CD4 cell count.
However, smokers who used HAART showed no such decreased risk for KS, with a HR of 2.14, report Michael Scheurer (Baylor College of Medicine, Houston, Texas, USA) and co-workers in the British Journal of Cancer.
Further analysis confirmed that the impact of smoking on KS was only found for men who did not use HAART (HR=0.57).
"Our findings should be interpreted cautiously, given the negative impact of smoking on general health and the null results from a previous clinical trial examining nicotine use on KS development," the researchers say.
"We, however, still think that to fully appreciate the impact that this finding might have on KS incidence among HIV-infected populations, the comprehensive biological mechanism of smoking in KS carcinogenesis needs to be elucidated."
The researchers used a cohort of HIV-positive men who have sex with men participating in the Multicenter AIDS Cohort Study, approximately 40% of whom were current smokers.
They recorded 530 incident cases of KS over 26,594 person-years of follow-up, giving an incidence of two cases per 100 person-years.
Scheurer et al note that previous research has suggested that nicotine may modify dendritic cell differentiation, producing atypical cells that may alter regulation of cytokines and T-cell response.
"Although the biological mechanism of smoking on carcinogenesis is not fully understood, this evidence provides a rationale for further investigation of the role of cigarette-smoking (i.e., nicotine) on KS risk," they suggest.
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