Patients with lung cancer who undergo surgical procedures have better survival rates than patients who don't, research has found.

However, according to the study, fewer of these patients are actually undergoing surgery.

Researchers from the University of California Davis Health System explored the reasons patients of the world's deadliest cancer don't get evaluated for surgery as part of a comprehensive treatment regimen.

In the study, which was published in The Annals of Thoracic Surgery, researchers analyzed more than 34,000 patients who had stage IIIA, IIIB or IV lung cancer. They found that patients who received surgery had improved survival rates compared to patients who did not.

"Treatment with chemotherapy is increasing, but surgical treatment is decreasing," Elizabeth David, UC Davis assistant professor of surgery and study author, said in a press release published in Science Daily.

"We have a treatment that we know improves survival when offered to appropriate candidates, but we're offering it to fewer people. We need to understand why this is happening," David added.

According to the research, surgery had a dramatic impact on overall survival rates of patients. Those who had chemotherapy and surgery survived for 40.7 months.

Others who received chemotherapy, surgery and radiation treatments survived for 33.3 months. Those who received surgery survived for 28.8 months, and those who had surgery and radiation survived for 18.6 months.

However, for patients who did not undergo surgery, those who had radiation and chemotherapy treatments survived for only for 11.9 months; chemotherapy alone was 10.5 months; and radiation alone was 3.7 months.

They also found that 27 percent of lung cancer patients received no treatment at all.

Researchers are yet to determine the reason patients refuse treatment. Some reasons they have considered were that people could be afraid of side effects, or other racial and socioeconomic biases.

According to David, the study is merely the "tip of the iceberg," adding that each patient is different and that data in the study may not be enough to give further answers.

Furthermore, the researchers aim to conduct more studies to determine which treatments will benefit patients better.

Lung cancer is the deadliest of all cancers, killing 1.4 million people each year.