The way lung cancer patients feel around the time they're diagnosed may be related to how long they survive -- even after taking into account objective measures of the disease, a new study suggests.

Researchers found that newly-diagnosed lung cancer patients who rated their quality of life higher generally lived longer with the disease: typically surviving nearly six years, versus less than two years among patients who'd reported a poor quality of life.

And objective measures -- like age, the stage and aggressiveness of the cancer and other health conditions -- did not fully explain the connection.

Quality of life is a "complex construct" that includes a person's feelings of physical, mental and emotional well-being, said Jeff A. Sloan, a professor of oncology and biostatistics at the Mayo Clinic in Rochester, Minnesota, who led the new study.

But doctors can begin to get at the issue by basically asking, "How are you doing?" Sloan said in an interview.

"That can start a conversation," he said.

Blood work and other lab tests are one way of seeing how a patient is doing, according to Sloan. But, he said, doctors have long been aware that two patients can look the same as far as objective cancer-related measures go, yet fare differently.

A number of studies have now shown that quality of life seems to affect the long-term picture for cancer patients, Sloan said.

So doctors at Mayo have begun routinely assessing cancer patients' quality of life, and some other cancer centers are starting to do the same, he added.

The current study, published in the Journal of Clinical Oncology, included 2,442 patients treated for lung cancer at Mayo over 11 years.

Around the time of their diagnoses, patients rated their overall quality of life on a standard scale of zero to 100. The researchers found that 21 percent had a "deficit" in quality of life -- or a score of 50 or lower.

Those patients survived for substantially less time: 1.6 years, on average, versus 5.6 years in the group with a higher quality of life around the time of diagnosis.

There were other differences between the two groups, too. Patients with a poorer quality of life were more likely to be men, current smokers and have more-advanced cancer, for example.

But even when Sloan's team factored in those differences, quality of life was still a predictor of survival time. Overall, the death rate during the study period was 55 percent higher among patients who gave low ratings to their quality of life.

So what can be done when cancer patients have quality-of-life issues? That depends on what seems to be underlying the problem, according to Sloan.

If it's depression or fatigue, medication or other treatment might help. Or if patients are having financial problems, there are government programs and non-profit groups that may be able to assist.

It's not clear yet whether assessing cancer patients' quality of life can actually prolong their survival.

Regardless, improving quality of life is an important goal by itself, Sloan said.

It turns out, though, that "quality" may depend on more than a patient's personal circumstances.

In a separate study in the same journal. Sloan's team found several specific gene patterns that were related to quality of life among 1,299 lung cancer patients.

Three variants of one gene thought to be involved in DNA repair were linked to a higher likelihood of reporting poor quality of life overall. Variations in some other genes associated with metabolism and pain were linked to higher or lower risks of fatigue, or a lower risk of pain.

Sloan said that researchers are continuing to study the role of genes in quality of life.

"We don't expect to find a 'quality-of-life gene,'" Sloan said. "It's more complicated than that."

But he did say he can envision a future where testing cancer patients for certain gene variations could help spot those who might "have a rougher ride" through treatment.

Doctors may be able to accomplish that just by asking about quality of life, Sloan acknowledged. But, he added, it could turn out that a combination of old-fashioned talking and genetic tests works best for figuring out who's most vulnerable.