Introduction Lung cancer accounts for 30% of all cancer deaths in the United States each year. Chronic inflammation has been linked to various steps involved in tumorigenesis. Several pro-inflammatory gene products have been identified that mediate a critical role in suppression of apoptosis, proliferation, angiogenesis, invasion, and metastasis. Among these gene products are Tumor Necrosis Factor (TNF), Interleukin (IL)-1a, IL-1b, IL-6, IL-8, and IL-18. The expression of all these genes is mainly regulated by the transcription factor nuclear factor kappa B (NF-kB), which is constitutively active in most tumors. Apnea-induced hypoxia and reoxygenation generates reactive oxygen species, which activate NF-kB and increase the systemic inflammation. Significant higher levels of pro-inflammatory cytokines TNF-α and IL-6, as well as a decrease in anti-inflammatory cytokines such as IL-10 has been found in obstructive sleep apnea (OSA). Previous studies showed that overnight oxygen desaturation seen in patients with OSA is associated with increased cancer incidence and cancer related mortality; The purpose of this study was to determine if OSA is an independent risk for the development and dissemination of malignancy, including lung cancer.
Methods This is a retrospective case control chart review study conducted at the Oklahoma City Veterans Affairs Medical Center (VAMC). All adult patients who had a sleep study done between January 1st, 2000 and December 31st, 2007 were included. Patients were divided into 2 groups, based on whether they have OSA or not. The primary outcome was the rate of lung cancer occurring between 1998 and 2012. The secondary outcome was the rate of all cancers occurring during the same period. Fisher exact test was used to compare these rates.
Results Nine hundred two patients with a sleep study done between 2000 and 2007 were reviewed. Fifty seven patients were excluded since complete sleep study data were not available. Seven hundred and seventy five patients had sleep apnea (91.7%). Lung cancer occurred in 26/775 (3.4%) patients with OSA, vs. 3/70 (4.3%) patients without OSA (p=0.7). The rate of all malignancies was 19% (148/775) in patients with OSA compared to 15.7% (11/70) in patients without OSA (p=0.6).
Conclusion Sleep apnea does not appear to increase the risk of malignancy in general, and that of lung cancer in particular. Further studies to account for confounding risk factors are needed to definitively answer this question.
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