Cessation of cigarette smoking and the impact on cancer incidence in HIV-positive persons: The D:A:D Study.     Clinical Infectious Diseases

Despite the well characterized harms of smoking in people living with HIV (PLWH), the clinical benefits of smoking cessation on cancer risk have not previously been reported in large epidemiological studies. The aim of this study was to estimate cancer rates after smoking cessation in PLWH from the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) Study.

Participants were followed from 1 January 2004 until first cancer diagnosis, death, or 1 February 2016. Smoking status was defined as ex-smoker, current smoker, and never smoker. Of note, smoking information is reported in the D:A:D Study as current smoker (yes/no) and ever smoker (yes/no) at each visit, but more specific information, such as cigarette or pipe smoking, or intensity of smoking, is not available.

In total 35’442 persons from the D:A:D study contributed 309’803 person-years of follow-up. At baseline, 49% were current smokers, 21% were ex-smokers, and 30% had never smoked.

• Incidence of all cancers combined (n = 2’183) was highest <1 year after smoking cessation compared to never smokers (aIRR, 1.66 [95% confidence interval {CI}, 1.37–2.02]) and not significantly different from never smokers 1–1.9 years after cessation.

• Lung cancer incidence (n = 271) was elevated <1 year after cessation (aIRR, 19.08 [95% CI, 8.10–44.95]) and remained 8-fold higher 5 years after smoking cessation (aIRR, 8.69 [95% CI, 3.40–22.18]). 

• Incidence of other smoking-related cancers (n = 622) was elevated in the first year after cessation (aIRR, 2.06 [95% CI, 1.42–2.99]) and declined to a level similar to nonsmokers thereafter.

In conclusion, incidence of lung cancer incidence in PLWH was >8-fold higher than never smokers several years after cessation, at a similar level to current smokers, and with no evidence of a decline after the first year. This suggests that the oncogenic potential for smoking is not reduced for lung cancer in the time frame that was investigated. This is in contrast with similar studies in HIV-uninfected people, which show a consistent decline in lung cancer incidence with increasing time since cessation. Deterring uptake of smoking and smoking cessation efforts should be a priority to reduce the risk of cancer; however, monitoring and awareness of lung cancer should continue in those who stop smoking. Studies following PLWH throughout their lifetimes are needed to determine when the benefit of cessation will be seen.

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