About a quarter of the people diagnosed with cancer in the U.S. are smokers, and well over half of them continue to smoke during treatment. What they may not realize is that they can prolong their lives even further — a year or more — by quitting.

There are many smoking cessation programs available for cancer survivors. The National Comprehensive Cancer Network, the American Society of Clinical Oncology and the American Association for Cancer Research all recommend them, but the programs are still underused in cancer care.

Eighty-five percent of late-stage patients who quit smoking were still alive after 540 days. Quitting added almost a year to survival.

One reason for this may be because many cancer patients and even providers think quitting smoking will not increase survival.

This is unfortunate and wrong. The findings of a new study from Washington University School of Medicine suggest that quitting can still be worth it — even for those with cancer.

“There is a big hole in our knowledge about the effectiveness of lifestyle changes, such as smoking cessation, when a person has cancer,” Li-Shiun Chen, a coauthor on the study, told TheDoctor.

Participants in the study who quit during the follow-up period had a survival rate that was 85 percent compared to 74 percent for those who did not quit. This was regardless of the type of cancer or stage of disease they had.

The researchers discovered this by analyzing the electronic health records of more than 13,200 patients who received outpatient cancer care at the Alvin J. Siteman Cancer Center of Washington University and Barnes-Jewish Hospital. Patients' smoking status was recorded at their first visit, and their rates of quitting smoking were tracked over the next six months. Of the more than 1,700 participants who said they were smokers at their first visit, about 22 percent had quit within six months.

Patients' survival rates were tracked over the next two years.

Quitting smoking can significantly extend cancer patients' lives, so it's important to find ways to let patients and providers know it's not too late to quit.

The biggest increase in survival rate over this time period was seen in patients with late-stage cancers (stages 3 or 4). Eighty-five percent of late-stage patients who quit smoking were still alive after 540 days, while the survival of 85 percent of those who continued to smoke was only 210 days. Quitting added almost a year to survival.

“Advanced-stage cancer patients often feel hopeless,” said first author Steven Tohmasi, a resident in the Department of Surgery at WSU Medicine. “If they feel they have limited time, some doctors might not actively encourage patients to quit smoking or may prioritize patient comfort over cessation efforts. But when we've shown patients our data, it gives them hope and motivates them to want to quit. An extra year of life is a long time for patients who may have been told they only had months to live.”

A patient's survival is affected by many factors, Chen, a professor of psychiatry at Washington University School of Medicine and director of the tobacco treatment program at the Siteman Cancer Center, explained. Many smokers have related health conditions such as heart disease, metabolic syndrome or high blood pressure that complicate survival.

The findings suggest how important it is to find ways to make providers aware of how much quitting smoking can benefit cancer patients and to let patients know it's not too late to quit.

The study is published in the Journal of the National Comprehensive Cancer Network.