VANCOUVER — Non-smokers who develop lung cancer might actually have a different disease than smokers, raising the possibility the two groups should be diagnosed and cared for differently, the preliminary results of a new study suggest.
Researchers at the BC Cancer Agency Research Centre examined the DNA of lung cancer tumours from 83 patients — 53 current or former smokers and 30 who have never smoked — and compared them with healthy cells from those same patients.
Cancer cells have different DNA patterns than healthy cells, and the researchers looked for those differences and compared them between the two groups.
What they found, according to results presented this week at an American Association for Cancer Research conference in Philadelphia, is that the cancer cells from non-smokers underwent different changes than the cells from the smokers.
“It’s very preliminary at this point, but the fact that we see differences between the tumours from the smokers and the non-smokers suggests that they probably arise in a different fashion,” Kelsie Thu, a PhD candidate at the cancer research centre and the lead author of the study, said.
“If they do have different mechanisms of development, it’s probably likely they could be treated as different diseases.”
The results are from a pilot study at the beginning of a three-year project and Thu stressed she and her colleagues still need to verify those results using different patients.
The pilot study also involved a relatively small sample size, although Thu said the results are statistically significant.
If they can duplicate their findings, Thu said, the next step will be to identify which genes are behind the differences and why.
“If we can better understand how these tumours develop and the biology underlying them, then we’ll be better able to develop new diagnostic or therapeutic markers specifically for this group of patients (who have never smoked),” said Thu.
“There are certain mutations that arise from smoking; we don’t really see those mutations in our non-smoker samples. I’m pretty confident they (non-smoker tumours) are coming up from a different pathway than smoke would cause.”
There are about 24,000 new cases of lung cancer diagnosed each year in Canada. Of those, Lung Cancer Canada estimates about 15 per cent affect non-smokers.
Currently, Thu said smokers and non-smokers who develop lung cancer are largely treated the same.
Wan Lam, a supervising researcher on the project, said as anti-tobacco campaigns continue to cut smoking rates, the proportion of lung cancer patients who have never smoked will likely increase.
“In the past, people always associated smoking with lung cancer, so if someone has lung cancer, you say, ’That’s because he smokes or she smokes,”’ Lam said in an interview in Vancouver.
“If we apply the same logic to all lung cancer, we may overlook things.”