Patients with lung cancer often have reduced physical fitness and coexisting health problems, which may limit their ability to tolerate oncological treatment. Standard resting lung and heart tests do not always reflect real-life physical capacity during everyday activities or physical effort.

This observational study aims to assess cardiorespiratory fitness in patients with lung cancer before and during standard oncological treatment using cardiopulmonary exercise testing (CPET). CPET is a safe, supervised exercise test that provides objective information on how the heart, lungs, and muscles respond to physical effort.

Participants with WHO/ECOG performance status 0-2 will undergo CPET before treatment initiation and again after the early phase of therapy or surgery. The results may help identify patients with reduced physiological reserve and support individualized monitoring during routine clinical care.

This prospective observational study assesses respiratory and exercise-related physiological parameters in adult patients with lung cancer who are qualified for standard oncological management, including surgical treatment and/or systemic therapy. Lung cancer patients frequently present with reduced functional capacity and relevant comorbidities, including cardiovascular risk factors, which may affect treatment tolerance. Resting pulmonary function tests and standard clinical assessments do not always reflect the integrated cardiorespiratory response to physical stress. Cardiopulmonary exercise testing (CPET) provides an objective and reproducible evaluation of the combined responses of the respiratory, cardiovascular, and metabolic systems during graded exercise.

The study is conducted in a tertiary university hospital setting. Patients are enrolled consecutively from routine clinical pathways. There is no assignment to any experimental intervention; all oncological treatments are delivered according to standard-of-care clinical decisions. CPET is the only study-specific procedure performed in addition to routine diagnostics and follow-up assessments. The planned enrollment is approximately 90 participants.

Study population and eligibility Eligible participants are adults (≥18 years) with histologically confirmed lung cancer (any stage) who are qualified for standard oncological management and have WHO/ECOG performance status 0-2. Written informed consent is required. Key safety-related exclusion criteria include unstable ischemic heart disease, symptomatic arrhythmias, myocarditis/pericarditis, decompensated heart failure, active deep vein thrombosis, suspected aortic dissection or severe aortic stenosis, poorly controlled asthma, resting oxygen saturation ≤85% on room air, clinically relevant treatment-related adverse events above mild intensity (as applicable), and withdrawal of consent.

Study assessments and timing

CPET is performed at two predefined time points for each participant:

Baseline assessment: prior to the initiation of standard oncological treatment (either before planned surgery or before initiation of systemic therapy).

Follow-up assessment after the early phase of treatment: approximately 6 weeks (±1 week) after surgery or approximately 6-8 weeks (±2 weeks) after initiation of systemic therapy, depending on the clinical pathway and feasibility.

These time points are intended to capture baseline physiological reserve and early treatment-related changes in exercise capacity. The primary evaluation focuses on change in key CPET measures between baseline and follow-up.

Cardiopulmonary exercise testing (CPET) procedure CPET is conducted using a standardized incremental protocol on a cycle ergometer under continuous supervision by trained personnel, with full medical safety measures available. Prior to exercise, resting assessments include symptom review, vital signs, and baseline electrocardiographic monitoring. During CPET, respiratory gas exchange is measured breath-by-breath and standard hemodynamic and ventilatory variables are recorded throughout the test. Exercise intensity increases in a stepwise or ramp fashion until symptom-limited maximal effort, clinical indication to stop, or achievement of standard termination criteria. Perceived exertion and dyspnea are recorded using standardized scales. Recovery monitoring is continued after exercise completion until clinical stability is confirmed.

CPET parameters of interest Key CPET-derived variables include peak oxygen uptake (VO₂peak), anaerobic threshold, ventilatory efficiency indices (including the VE/VCO₂ relationship), and additional exploratory measures of ventilatory limitation and circulatory response as available from standard CPET output. These parameters are used to characterize cardiorespiratory reserve, identify potential exercise-limiting mechanisms, and evaluate within-subject changes over time.

Routine clinical data collection In addition to CPET, routinely collected clinical information is recorded for descriptive and exploratory analyses. This may include demographic data and clinical characteristics, smoking history, comorbidities (including cardiovascular disease and risk factors), performance status, anthropometric measures (height, weight, body mass index), resting oxygen saturation, standard pulmonary function tests (spirometry with bronchodilator testing, lung volumes/plethysmography where available, diffusing capacity), resting electrocardiography, and standard laboratory parameters commonly used in oncological qualification and monitoring. Imaging studies and cardiac assessments performed as part of routine care (e.g., computed tomography staging, echocardiography when clinically indicated) may be documented. The study does not mandate additional imaging or laboratory procedures beyond standard clinical practice.

Safety considerations CPET is performed in a controlled clinical environment and follows established safety standards. Participants are screened for contraindications prior to testing. Any adverse events related to testing are documented and managed according to institutional procedures. The study does not introduce therapeutic interventions, and participation does not alter the standard oncological treatment plan.

Study objectives The primary objective is to characterize baseline cardiorespiratory fitness and to evaluate early changes in exercise tolerance during standard oncological management in patients with lung cancer. Secondary objectives include identification of patients with reduced physiological reserve who may be at increased risk of exercise intolerance or clinical decompensation during treatment, and exploratory assessment of associations between CPET measures and routine clinical characteristics.

Potential significance By providing objective and repeatable measures of functional reserve, CPET-based assessment may support individualized monitoring in routine clinical care and may improve understanding of treatment-related functional changes in lung cancer patients.

Inclusion Criteria:

• Age ≥ 18 years
• Histologically confirmed lung cancer (any stage)
• Qualified for standard oncological management (surgery and/or systemic therapy)
• WHO/ECOG performance status 0-2
• Ability to perform cardiopulmonary exercise testing (CPET)
• Written informed consent

Exclusion Criteria:

• Unstable ischemic heart disease
• Symptomatic cardiac arrhythmias
• Myocarditis or pericarditis
• Decompensated heart failure
• Active deep vein thrombosis
• Suspected aortic dissection or severe aortic stenosis
• Poorly controlled asthma
• Resting oxygen saturation ≤ 85% on room air
• Clinically relevant treatment-related adverse events above mild intensity (as applicable)
• Any medical condition that, in the investigator's opinion, precludes safe participation in CPET
• Withdrawal of informed consent

Adult patients (≥18 years) with histologically confirmed lung cancer (any stage) and WHO/ECOG performance status 0-2, treated with standard oncological management in a tertiary university hospital and undergoing cardiopulmonary exercise testing before treatment initiation and after the early phase of therapy or surgery.