Nicotine is the most common preventable cause of death and is responsible for over seven million deaths worldwide. If current trends continue, tobacco will kill more than eight million people worldwide every year by 2030. Smoking tobacco products is the most important risk factor for the development of lung cancer. Passive smoking is also a major cause of lung cancer. Since July 2024, smokers and former smokers have been able to receive a low-radiation CT scan under certain conditions to detect lung cancer at an early stage. It is therefore to be expected that the number of diagnoses of pulmonary lesions or nodules will increase in the near future. The risk of developing and dying from tobacco-related diseases is reduced once nicotine cessation begins. Screening all patients for tobacco use, e-cigarette use, and providing behavioral counseling and pharmacotherapy to quit smoking are among the most valuable preventive services we can offer in healthcare.

Nicotine dependence can be estimated using the so-called Fagerström test. An additional evaluation of nicotine behavior can be carried out by testing cotinine in urine, a method that is used, for example, in the listing for lung transplantation. Cotinine is a degradation product of nicotine that can be detected in the urine of smokers and passive smokers. Cotinine levels in urine depend on the frequency and quantity of nicotine consumption. The half-life of cotinine is 16 to 22 hours, which means that half of the cotinine is excreted from the body after this time. Another marker that can be used as a measure of tobacco consumption is carboxyhaemoglobin (COHb). This is hemoglobin with carbon monoxide at the binding site for oxygen. The reference range for carboxyhaemoglobin is 0.4 - 1.6 %. In smokers, values of 3-10 % are still considered normal.

In our department, the smoking status of patients is assessed upon first contact. Support options for smoking cessation are offered and, upon request, initiated. Previous studies have shown that smoking is a risk factor for complications after thoracic surgical procedures and that patients who underwent thoracic surgery quit smoking almost twice as often compared to patients who did not undergo surgery. However, to the best of our knowledge, there is currently no study regarding smoking cessation before intervention in patients with nodules needing clarification (bronchoscopy or CT-guided puncture).

Therefore, the aim of the study is to support and monitor smoking cessation before intervention in patients with nodules needing further diagnosis (bronchoscopy or CT-guided puncture).

Patients who present to our outpatient clinic for the evaluation of a concerning round lesion (V1) are asked during the medical history taking whether they currently smoke. If the question is answered affirmatively, patients are urgently advised to quit smoking immediately. Support options for smoking cessation are presented, and if desired, a connection to a smoking cessation counseling program of the Federal Institute for Public Health ('rauchfrei ticket') is established. Furthermore, nicotine dependence is assessed using the Fagerström test, while COHb is determined through blood gas analysis and cotinine is measured in urine. During the planned result discussion (V2) after the inpatient stay for histological confirmation (either via bronchoscopy or CT-guided puncture), patients are asked if they have quit smoking and COHb and cotinine are measured again. After 3 months (V3), these values will be measured conclusively. In addition, the following data will be collected and documented from the patients: age, gender, height, weight, current medication, other illnesses, and current body plethysmography. Participation in the study does not change the course of the patients' stay in our clinic.

Inclusion Criteria:

• The patient is an active smoker by the time of the initial presentation in our pneumological outpatient clinic for the clarification of a suspicious nodule

Exclusion Criteria:

• Current or past medically relevant illness or treatment that could affect the evaluability of the study.
• Expected lack of willingness to actively participate in study-related measures.

Active smokers by the time of the initial presentation in our pneumological outpatient clinic for the clarification of a suspicious nodule