(Reuters Health) – Prostate cancer patients who smoke are more likely to return to tumors, spread to other parts of the body and become fatal than non-smokers, a new study suggests.
Researchers examined data from previous studies with a total of 22,549 men with prostate cancer who had not spread to other parts of the body. The cancers were treated with surgery or radiation.
In general, almost one in five were current smokers. The rest were former smokers or had never smoked.
Researchers tracked half of the men for at least six years. During follow-up, compared to men who never smoked, current smokers were 40 percent more likely to have tumors after treatment and more than twice as likely to have cancer spread beyond the prostate. Smokers were also 89 percent more likely to die of cancer.
"The diagnosis of prostate cancer, even when it is not associated with smoking, is an appropriate time for patients to stop smoking," said the study's lead author, Dr. Shahrokh Shariat of the Medical University of Vienna in Austria.
"Previous smoking was associated with an increased risk of relapse, but not with the spread or cancer-specific death, which underscores the importance of quitting smoking to improve the outcome of the disease," Shariat said by mail electronic. In fact, he added, men who had quit smoking more than 10 years earlier "were not significantly different from patients who had never smoked."
Not all men with localized prostate tumors receive aggressive treatment with surgery or radiation. Often, men with this type of tumor will opt for more conservative alternatives, such as watchful waiting or hormone therapy to reduce tumors without surgery or radiation.
Smoking for a long time has been linked to an increased risk of death from a variety of malignancies, including the lungs, bronchi, trachea and larynx, stomach and kidneys.
"We know that smoking produces more than 70 carcinogens," Shariat said.
It is not clear exactly how smoking could cause prostate cancer to develop it or make it more aggressive or more fatal. One possibility is that smoking causes inflammation, which in turn stimulates the growth of tumors, or that nicotine causes the spread of malignant tumors, Shariat said.
The smallest studies in the current analysis that analyzed cancer-related deaths had a total of 7,924 participants. Overall, 654 men, or about 8 percent, died when researchers followed half of them for about eight years.
The present study was not a controlled experiment designed to test whether smoking influences the chances of dying from prostate cancer. The researchers also based the analysis on smoking status when patients were in treatment, and it is possible that some patients have stopped or started smoking after that.
Smokers may also be less compatible with treatment than non-smokers, said Dr. Stephen Freedland, author of an accompanying editorial and director of the Center for Integrated Research on Cancer and Lifestyle at Cedars-Sinai Medical Center in Los Angeles.
But because the study looked at men undergoing aggressive treatment, it is unlikely that noncompliance would have influenced patient outcomes, Freedland said by email.
"Cigarettes themselves have chemicals that can cause cancer," said Freedland.
"This is clearer in the lung where smoke is inhaled," Freedland added. "However, the fact that death from prostate cancer is related to the means of smoking (these causes of cancer) are not only present in the lungs but are also absorbed in the body and reach the prostate and, as such, they probably make their way to every organ of our body. "
SOURCE: bit.ly/2M2LqFg and bit.ly/2M0M6L JAMA Oncology, online May 24, 2018.