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Avoiding smoking could prevent 37% of non-AIDS cancers in adults with HIV
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CROI 2015, February 23-26, 2015, Seattle, Washington
CROI: Avoiding smoking could prevent 37% of non-AIDS cancers in adults with HIV....."Smoking Outweighs HIV-related Risk Factors for Non-AIDS-defining Cancers".....'CD4 >200 & viral load matter too in cancer prevention'....modifiable risk factors to prevent cancer - (03/09/15)
Mark Mascolini
Programs that prevent smoking in adolescents at risk for HIV infection could prevent up to 37% of non-AIDS cancers in HIV-positive adults, according to a 39,000-person analysis of the North American NA-ACCORD study group [1]. By keeping CD4 counts high and viral loads low, successful antiretroviral therapy could prevent up to 8% of non-AIDS cancers, the NA-ACCORD team calculated.
Keri Althoff (Johns Hopkins Bloomberg School of Public Health) and NA-ACCORD colleagues who conducted this study observed that cancer ranks among the top three non-AIDS causes of death in adults with HIV. But whether interventions that address cancer risk factors in HIV-positive people would make cancer less frequent remains unknown. To address that question, Althoff and colleagues figured the population-attributable fraction for leading cancer risk factors, defining that fraction as "the proportion of cancers avoidable for a given risk factor if all participants had the reference group exposure level" [2].
The study group included adults from 16 NA-ACCORD cohorts tracked for validated non-AIDS cancers from January 2000 through December 2009. Traditional cancer risk factors were smoking, high total cholesterol, statin use, hypertension, diabetes, and stage 4 chronic kidney disease. HIV-related factors were CD4 count, detectable viral load, clinical AIDS diagnosis, and antiretroviral use. Other risk factors were hepatitis B and C infection. The researchers did not have information on alcohol use, body mass index, of human papillomavirus infection. They measured all variables for each participant at study entry.
During follow-up 592 of 39,554 cohort members (1.5%) had a non-AIDS cancer diagnosis. People in whom cancer developed were older and more likely to have (1) a smoking history, (2) hepatitis B or C, (3) a low CD4 count, and (4) a clinical AIDS diagnosis. Among people diagnosed with cancer, 82% ever smoked compared with 64% in the noncancer group. Proportions in four HIV transmission risk groups did not differ substantially between the cancer group and the noncancer group.
The most frequent non-AIDS cancers were lung cancer (17%), anal cancer (16%), prostate cancer (10%), Hodgkin lymphoma (9%), liver cancer (7%), and breast cancer (7%). No other non-AIDS cancer made up more than 5% of non-AIDS cancers.
Population-attributable fraction was highest by far from smoking--regardless of whether the analysis included lung cancer (see list below and Figure 1 in linked e-poster). Baseline CD4 count below 200 (versus higher) had the next-highest population-attributable fraction, followed closely by clinical AIDS, viral load above versus below 400, and HBV infection:
Population-attributable fraction including and excluding lung cancer:
-- Ever smoking: including lung cancer 37%; excluding lung cancer 29%
-- CD4 count below 200: including lung cancer 8%; excluding lung cancer 8%
-- Clinical AIDS diagnosis: including lung cancer 6%; excluding lung cancer 5%
-- Viral load above 400 copies: including lung cancer 4%; excluding lung cancer 5%
-- HBV infection: including lung cancer 3%; excluding lung cancer 4%
Althoff and coworkers explained that these population-attributable fractions mean, for example, that getting adolescents at risk for HIV infection to avoid smoking could prevent up to 37% of non-AIDS cancers if they became infected. Among infected people, using antiretroviral therapy to maintain a high CD4 count and an undetectable viral load could prevent up to 8% of non-AIDS cancers.
Cox proportional hazards models adjusted for age, sex, race, and all risk factors in the above list (plus HCV infection) determined that ever smoking raised chances of all non-AIDS cancers considered including lung cancer 82% (adjusted hazard ratio [aHR] 1.82, 95% confidence interval [CI] 1.41 to 2.35). If the analysis excluded lung cancer, ever smoking raised non-AIDS cancer risk 54% (aHR 1.54, 95% CI 1.18 to 2.00). Risk for all non-AIDS cancers considered was 34% higher with a CD4 count below versus above 200 (aHR 1.34, 95% CI 1.11 to 1.62), and risk was similar with a sub-200 CD4 count for non-AIDS cancers excluding lung cancer. HBV infection independently raised the risk of all non-AIDS cancers considered 60%, and clinical AIDS raised the risk of all non-AIDS cancers 24%.
"To reduce the [non-AIDS cancer] burden in HIV-infected adults," the NA-ACCORD team concluded, "effective interventions to reduce smoking are needed with a continued focus on HIV treatment."
References
1. Althoff K, Gange S, Jacobson L, et al. Smoking outweighs HIV-related risk factors for non-AIDS-defining cancers. CROI 2015. February 23-26, 2015. Seattle, Washington. Abstract 726. For the e-poster: www.croiconference.org/sites/default/files/posters-2015/726.pdf
2. Laaksonen MA, Harkanen T, Knekt P, Virtala E, Oja H. Estimation of population attributable fraction (PAF) for disease occurrence in a cohort study design. Stat Med. 2010;29:860-874.
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