Prostate cancer mortality risk raised in smokers
MedWire News: Men who are current smokers at the time of a prostate cancer diagnosis have a higher risk for dying from the disease compared with men who do not smoke, and former smokers who gave up more than 10 years previously, show study results.
Smoking at the time diagnosis occurs also raises the risk for cardiovascular mortality and biochemical disease recurrence after treatment compared with not smoking, add the researchers.
"These data are exciting because there are few known ways for a man to reduce his risk of dying from prostate cancer," said study co-author Edward Giovannucci (Harvard Medical School, Boston, Massachusetts, USA).
"For smokers, quitting can impact their risk of dying [from the disease]. This is another reason not to smoke," he added.
Giovannucci and colleagues used data from 5366 men from the Health Professionals Follow-Up Study who were diagnosed with prostate cancer between 1986 and 2006 to investigate the impact of smoking on their outcomes.
After a median 6.5-year follow up there were 1630 deaths in all, with 524 attributed to prostate cancer, and 416 to cardiovascular disease. A total of 878 men experienced biochemical disease recurrence after a median 3.8 years.
Overall, just 5.2% of men reported current smoking at the time of their prostate cancer diagnosis.
The absolute crude rates per 1000 person-years of follow up for prostate cancer-specific mortality were 9.6 for never-smokers (n=2449), 10.3 for former smokers who had quit for more than 10 years (n=2063), 13.8 for former smokers who had quit less than 10 years previously (n=297), and 15.3 for current smokers (n=277).
A similar pattern was noted among these men for disease recurrence during the same follow-up duration, with corresponding rates of 26.4, 28.1, 34.6, and 38.2, respectively.
In multivariate analysis, current smokers had a significantly increased risk for death from prostate cancer, cardiovascular mortality, all-cause mortality, and biochemical recurrence compared with never smokers, with hazard ratios (HRs) of 1.61, 2.13, 2.28, and 1.61, respectively.
After further adjustment of results for stage and grade of disease - potentially confounding factors - these associations remained significant.
A greater number of pack-years of smoking also increased prostate cancer, total, and cardiovascular mortality risk in former smokers, but not the risk for recurrence, note the researchers in JAMA. However, in current smokers, 'daily dose' (cigarettes per day) had no significant effect on these outcomes.
All former smokers had a 23% increased risk for prostate cancer mortality compared with never-smokers, reports the research team. However, those who had quit for more than 10 years or who had quit for less than 10 years but smoked for a total of less than 20 pack-years had similar prostate cancer mortality risks to never smokers (HRs=0.60, 0.61, and 0.61, respectively).
"A direct effect of smoking is biologically plausible," conclude the researchers, who include tumor promotion through carcingens in tobacco smoke, increased levels of total and free testosterone in smokers, epigenetic effects that correlate with aggressive disease, and nicotine-induced angiogenesis, capilliary growth, and tumor growth and proliferation caused by cigarette ingredients.
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By Sarah Guy