Smoking may increase the risks of patients being treated for prostate cancer, according to a new study.

A team of researchers studied 2,358 patients who were classified as never smokers, current smokers, former smokers and current smoking unknown. Of these patients, 2,156 people had at least some smoking history. 

After eight years, during a median checkup, patients who were current smokers had a 40 percent increased risk of cancer relapse, and more than two-times increased risks of cancer spread and cancer-related death, according to a news release.

Both current and former smokers had a higher likelihood of experiencing side effects - including urinary toxicity, related to radiotherapy. 

"Less optimal tumor control outcomes among smokers could possibly be explained by the influence of less oxygen concentration within the treated tumors among smokers, which is known to lead to less sensitivity of the cells being killed off by radiation treatments," Dr. Michael Zelefsky said in the release. "Our findings point to the importance of physicians counseling their patients regarding the potential harms of smoking interfering with the efficacy of therapies and for increased risks of side effects." 

Other studies in the past have linked smoking to prostate cancer, but this study helped the researchers better understand the effects of patient's side effects from treatment, the development of future cancer recurrences, as well as complications related to their care. 

The study was published in the journal BJU International.