There have not been many studies looking at an association between obstructive sleep apnea and cancer. It's possible that obstructive sleep apnea theoretically could increase risk of cancer due to inflammatory changes, oxidative stress, possible immune dysfunction, and intermittent low oxygen levels. This study with a large population from Denmark with purple work or study. The researchers assessed possible obstructive sleep apnea by asking him questions about snoring, stopping breathing while asleep, and subjective daytime sleepiness. No subsided for performed, so short of sleep apnea was not officially diagnosed or ruled out in this population. The researchers then compared the incidence of developing cancer with the obstructive sleep apnea symptoms.
The results did not show any significant association between snoring, history of stopping breathing while asleep, or sleepiness with incidence of cancer. However, as reviewed in the article, assessing for the presence of obstructive sleep apnea by just asking patients about their symptoms is not all that accurate. It would be better for these patients to have had sleep studies to actually determine if obstructive sleep apnea was present.
This study does not support a strong association between obstructive sleep apnea symptoms and risk of cancer. More studies need to be undertaken to determine if an actual diagnosis made from a sleep study is associated with elevated risk of developing cancer. And then whether or not treating the obstructive sleep apnea reduces that risk.