Our retrospective study investigated the association between lung cancer occurrence and COPD or emphysema in smokers.
We noted the significant correlation between smoking history and size of tumor and risk of lung cancer.
We also found,
that there is no statistically significant association between the incidence of lung cancer and COPD,
regardless of the severity of airflow obstruction.
Additionally no statistically significant correlation was found between the incidence of lung cancer and emphysema,
regardless of severity and type of the disorder.
The correlation between smoking and size of the tumor and risk of malignancy is well known.
We confirmed results from numerous other studies.
[8,
9,
10]
However,
our study contradicts several reports,
that airflow obstruction is a risk factor for lung cancer development [4,
7,
11,
12,
13].
Some reports indicate that COPD elevates the risk for lung cancer independently of other risk factors,
such as sex,
age and smoking history,
with a greater risk of developing lung cancer when compared to matched smokers with normal lung function.
In some studies,
the risk increases with progressive declines in FEV1 [2,
14,
15].
However,
one study reported a paradoxical decrease in the risk of lung cancer development with the increase of airflow obstruction in COPD patients [16].
The possible explanation of our results is a small group of included patients.
In our study,
we examined only 63 patients with lung cancer,
and this is a possible risk of bias.
Also,
our control group did not consist of healthy individuals – all of our patients were smokers,
and all have suspected nodules required diagnostic work-up.
The strong weakness of our study is that we did not add to control group emphysema results from all participants especially those with negative LDCT result,
and that point needs to be evaluated in future analysis.
Smoking is a risk factor for lung cancer,
as well as COPD and emphysema.
Thus,
the coexistence of those entities could also reflect a shared smoking exposure.
Approximately 85% lung cancers occur in smokers,
and 96.6% of lung cancer patients with COPD are smokers [17].
All the patients in our study had a history of at least 20 pack-years of smoking,
or,
in case of patients with high risk of developing lung cancer,
at least 10 pack-years.
This implicates,
that they were all at risk of developing lung cancer,
as well as COPD and emphysema.
Also,
our study took place in Pomeranian region in Poland,
which is mostly inhabited by a mono-ethnical population.
Our observations may not be valid in other populations.
In conclusion,
participants with detected lung cancer tends to have higher exposition to tobacco smoke and to have a larger lung nodule.
But,
we found no statistically significant association between COPD or emphysema in smokers in our population.
This outcome contradicts several other studies in this field.
A possible explanation of this results is,
that only long-term smokers with highly suspicious positive LDCT results were included to analysis.
Further studies,
including all lung cancer screening participants,
especially those with negative LDCT result, are needed.