A recent Norwegian study found that lung cancer patients who also have diabetes often live longer than patients who do not have diabetes. The study was published in the “Journal of Thoracic Oncology,” the official journal associated with the International Association for the Study of Lung Cancer.

The research team did not offer any theories about the underlying mechanism that causes the relationship, but did note that additional research was warranted. Additionally, they commented that the relationship did not constitute a justification for withholding standard cancer treatment from individuals with diabetes.

“Standard therapy should not be withheld from patients with diabetes mellitus provided they are otherwise fit, even if it may be considered a significant comorbidity,” wrote the researchers. “The survival benefit may be of clinical importance and should be focused on in future studies,” they added.

The study was conducted jointly by the Norwegian University of Science and Technology and Trondheim University. Researchers analyzed data from 1,677 lung cancer patients across three studies: the Nord-Trøndelag Health study (HUNT), the pemetrexed gemcitabine (PEG) study, and the Norwegian Lung Cancer Biobank study. The investigation was the first of its kind, being a cohort study confined to a particular geographical area with a large and stable population which looked at possible links between diabetes, lung cancer, and patient survival rates.

The researchers found that, in patients with both lung cancer and diabetes, survival rates were consistently higher across the follow-up period. After one year, survival in patients with lung cancer and diabetes was 43 percent compared to 28 percent without diabetes; at two years, survival rates were 19 percent compared to 11 percent; and at three years, survival rates were 3 percent compared to 1 percent.

The research team noted that the lower incidence of metastatic diseases in patients with diabetes could partly explain the unexpected differences in survival rates:

“The fact that patients with diabetes mellitus showed a lower frequency of metastatic diseases may partly explain the survival benefit in patients with diabetes mellitus, because the majority of the patients with lung cancer die of metastasis and not of the primary tumor,” they wrote.

After the researchers adjusted for the severity of diseases, however, it became clear that diabetes patients survived longer. Even patients with advanced lung cancer survived longer when they had diabetes.

“However, as we adjusted for stage of disease in our analyses this potential advantage can hardly explain the observed increased survival in patients with diabetes mellitus. In addition, increased survival in patients with diabetes mellitus was clearly demonstrated in the PEG study where all patients had advanced lung cancer.”

“Patients with lung cancer with diabetes mellitus have an increased survival compared with those without diabetes mellitus,” concluded the research team.

Lung cancer is the most dangerous form of cancer in the United States, claiming more lives than any other type, in both men and women. In 2007, over 200,000 patients received diagnoses of lung cancer, while over 150,000 died from the disease. Still, lung cancer rates have been decreasing in men for years while slowly rising in women. According to the American Cancer Society, risk of developing cancer for men is about 1 in 13, while risk for women is about 1 in 16. Lung cancer affects both smokers and non-smokers, although risk significantly increases in smokers. Lung cancer is typically a very serious diagnosis, though about 400,000 people today have been diagnosed with lung cancer and beat the disease.