New research suggests that smokers with chronic obstructive pulmonary disorder (COPD) have an increased risk of developing lung cancer than those without the disease.

Researchers at Harvard University found that smokers with COPD may face nearly twice the risk of getting small cell lung cancer (SCLC)--the deadliest form of lung cancer.

"This work suggests that we need to tease out the mechanisms by which COPD may increase lung cancer risk in smokers, and to conduct clinical trials to determine whether treating COPD in former and current smokers lessens that risk," David Christiani, senior author of the study and Elkan Blout Professor of Environmental Genetics at Harvard Chan School, said in a statement.

SCLC has a high relapse and mortality rate and accounts for 15 to 18 percent of lung cancers worldwide. Although patients often respond well to initial treatment, they often relapse within a year. Those with limited SCLC live, on average, 14 to 20 months after diagnosis; those with extensive disease live only 9-11 months after being diagnosed.

For the study, researchers analyzed data from 24 case-control studies from the International Lung Cancer Consortium that included 4,346 people with SCLC and 37,942 without the disease.

Their analysis showed that smokers with COPD had a 1.86-fold higher risk of SCLC than smokers. They also found that COPD accounted for 8 percent of SCLC cases among smokers.

The findings are detailed in the journal EBioMedicine.