How long patients survive after surgery to remove lung cancer may depend on factors like insurance, income and education, according to a new study.

While the stage of the cancer is a more important influence on patient outcomes, the study’s senior author said understanding all of the factors tied to survival can identify groups of people who need more attention for quality improvement.

“We can start improving access for certain patients,” said Dr. Felix G. Fernandez of The Emory Clinic in Atlanta, Georgia.

He and his team used the National Cancer Data Base to identify almost 235,000 patients who were diagnosed with non-small cell lung cancer between 2003 and 2006. Close to 93,000 of them underwent surgery to remove the cancer.

Lung cancer patients who do receive surgery have higher odds of survival from the start.

About 60% of patients diagnosed with stage I cancer survived at least five years after surgery, compared to 40%, 31% and 20% for stage II, III and IV, respectively.

Patients with higher stage or larger tumors, positive lymph nodes and older age at diagnosis were more likely to die during follow-up than others.

After accounting for those factors, a lack of insurance, lower income and lower education level were associated with worse overall survival after surgery, according to results online October 27 in the Journal of the American College of Surgeons.

Patients with the lowest education level and lowest income level had a 10% increased risk of death and not being insured imparted a 23% increased risk, Fernandez said.

“The impact of some of these things is certainly not as powerful as the stage of the tumor,” Fernandez said. “The extent of the cancer drives survival more than anything else.”

Also, it’s hard to determine how the socioeconomic factors work together. He said these factors don’t add up to a sum total of risk, but they do all tend to apply to the same group of people.

“It's not well understood why these factors influence outcomes after surgery,” said Dr. Mark K. Ferguson, who was not involved with the new study but is a lung surgery specialist at The University of Chicago’s Department of Surgery and its Cancer Research Center.

“They likely influence the type of center at which patients are treated, and that may have an effect on the accuracy of staging and the type of treatment recommended,” he told Reuters Health by email.

People treated at community health centers were more likely to die than those treated at academic or research institutions, the authors write.

Patients at recognized centers undergo more appropriate operations that are likely performed by more specialized and better trained surgeons, Ferguson said.

“In addition, the quality of follow-up care (or lack thereof) can also have an important impact on outcomes,” he said, adding that they did not evaluate that in the current study.

In some cases patients have a choice for where they receive care and in some cases they do not, Fernandez said. Most academic research hospitals take Medicare or Medicaid and even offer some charity care, he noted, but some low-income patients may not have the means to travel to one of these centers.

“Fixing these things as you can imagine is very complex, but without identifying the disparities we don’t even know which groups are at risk,” he said.

These socioeconomic factors are probably universal and would likely apply to heart surgery, colon cancer or non-operative lung cancer, he added.