The study, investigates the current physical activity promotion practices among physicians and nurses, as well as social norms toward physical activity during treatment among cancer patients and among physicians and nurses who treat or counsel cancer patients.

For this purpose, four large surveys with health care professionals (specialized practitioners, N=300; general practitioners, N=300; oncology nurses, N=300) and cancer patients (N=1200, 400 patients each with breast, prostate or colorectal cancer) with a cross-sectional research design are conducted.

Additionally, a follow-up-study with a sub-sample of cancer patients (N=180) will be conducted.

Inclusion Criteria:

• HCP are eligible if they meet the following inclusion criteria: Working as an oncological nurse, general practitioner or physician specialized in oncology, radiology, surgery, gynecology, urology, gastroenterology or rehabilitation Signed informed consent
• Patients are eligible if they meet the following inclusion criteria: Patients with a diagnosis of primary tumor or recurrence no longer than 2 years ago who are undergoing chemo- or radiotherapy currently or in the last 2 years Patients undergoing chemo- or radiotherapy currently or no longer than 2 years ago At least 18 years of age Sufficient German language skills Signed informed consent

Exclusion Criteria:

• HCP will be excluded from the trial if they meet the following exclusion criteria: No regular contact with cancer patients
• Patients will be excluded from the trial if they meet the following exclusion criteria: Presence of comorbidities that preclude involvement in exercise programs (e.g. severe pain, advanced heart failure [≥ NYHA III]) Mentally retarded Reduced standing ability and no ability to walk

Cross-sectional surveys:

1. 300 specialized practitioners who treat patients with breast, prostate or colorectal cancer (gynecologists, radiologists, urologists, gastroenterologists, oncologists, surgeons)
2. 300 general practitioners
3. 50 rehabilitation physicians
4. 300 oncology nurses
5. 1200 cancer patients with breast, prostate or colorectal cancer before or during cancer therapy (pre-treatment and primary cancer treatment time period according to PA and Cancer Control (PACC) framework)
6. Longitudinal follow-up study: 180 patients [sub-sample of (5)] who are recruited before the initiation or at the beginning of their primary cancer treatment