Lung cancer patients with diabetes tend to live longer than patients without diabetes, according to a Norwegian study published in the November issue of the Journal of Thoracic Oncology, the official publication of the International Association for the Study of Lung Cancer.

"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," researchers wrote in the study. "The survival benefit may be of clinical importance and should be focused on in future studies."

Researchers at the Norwegian University of Science and Technology and Trondheim University analyzed 1,677 lung cancer cases from the Nord-Trondelag Health study (HUNT), the pemetrexed gemcitabine (PEG) study and the Norwegian Lung Cancer Biobank study. It was the first cohort study from a well-defined geographical area, with a stable and large number of inhabitants, investigating lung cancer, diabetes and survival.

They found that the 1-, 2-, and 3-year survival in patients with lung cancer with and without diabetes mellitus were 43% versus 28%, 19% versus 11%, and 3% versus 1%, respectively.

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, researchers wrote. "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."

Researchers did not speculate on the reason for the effect, but said that the survival benefit warranted more study and that diabetes should not be considered a reason to withhold standard cancer treatment.