This trial investigates the impact of lung cancer treatment on physical status, symptoms and quality of life. Furthermore this trial investigates possible underlying causes and consequences of deconditioning.

Preliminary evidence suggests that patients with lung cancer experience a decrease of exercise tolerance and muscle strength during the course of their treatment. The underlying mechanisms and impact of this change has not yet been investigated. In light of this, our trial will prospectively follow a convenience sample of 150 patients with lung cancer who are undergoing treatment. Patients will be assessed before, during and at the end of the treatment (surgery and/or chemotherapy and/or radiotherapy and/or immunotherapy). The aims of the study are to

1. Investigate physical status, before start of treatment in lung cancer patients in comparison with healthy controls (primary outcome).
2. Investigate changes in physical status over the course of treatment in lung cancer patients (primary outcome).
3. Investigate the relationship between changes in physical status with physical activity and symptoms during treatment for lung cancer (secondary outcome).
4. Investigate the relationship between physical status after treatment for lung cancer and comorbidities, hospitalizations and cancer-related and all-cause mortality (exploratory outcome).

Inclusion Criteria:

• undergoing treatment (surgery, chemotherapy, immunotherapy, radiotherapy, and combination of the previous ones)
• WHO performance status of maximal 2

Exclusion Criteria:

• presence of other neoplasms in the last 2 years
• bone metastasis
• progressive neuromuscular and neurological diseases
• unstable cardiac disease
• pulmonary hypertension
• interstitial lung disease
• orthopedic conditions that significantly impair functional status
• mental or psychiatric disorders that impair the ability to comply with study procedures.
• a history of cerebrovascular accident with remaining functional consequences
• a history of lung cancer
• difficulties in understanding and speaking Dutch

Consecutive patients with a primary diagnosis of non-small-cell lung cancer who will undergo treatment (surgery, chemotherapy, immunotherapy, radiotherapy, and combination of the previous ones) and score a maximal of 2 on the WHO performance status classification, will be eligible for inclusion.

Healthy matched volunteers will carry out the same assessments once.