Table A1.

Question	Heading	Subheading	Examples of utterances coded
1. Do you think that cancer patients should be involved in decisions regarding their treatment?a
	Conditions for involvement	Information	Being able to understand information about alternatives; right to receive information
		Patient-clinician relationship	Clinician's honesty; patient's trust in clinician; clinician's clarity of information
		Decision	There is a choice to be made
	Roles in decision-making process	Patient	Patient autonomy; patient chooses what he/she considers as quality; patient carries responsibility; patient thinks along
		Clinician	Clinician has the expertise; clinician advises; clinician is responsible
	Outcome of decision-making process		Patient and clinician reach agreement; motivated patient endures the treatment better
	Legal obligation	Informed consent procedure	Need to comply to the informed consent procedure
2. If so, do you think all patients are able to be involved in deciding about their treatment?b
	Psychological inabilityc		—
	Emotional barriers		Patient is too anxious; patient is emotionally unstable; patient lacks confidence
	Cognitive barriers		Patient has limited intelligence; patient has difficulties with appraising risks; patient does not understand the information
	Socio-demographic factors		Patient stems from an older generation; patient lacks social support; patient holds particular religious beliefs
	Co-morbidity		Dementia; intellectual disability; psychiatric disorder
	Complex situation		Patient is unfamiliar with decision situation; information is complex
3. If a patient does not want to be involved in deciding about treatment, do you think that physicians should nevertheless try to involve their patient in deciding about treatment? d
	Reason why	Patient: Temporary evasive behaviour	Patient feels panicky; it is important to help prevent regret in patient
		Patient: Responsibility	Patient is (also) responsible; patient has to live with the consequences; patient is autonomous
		Clinician	It is clinician's task; clinician needs patient agreement
		Patient-clinician relationship	Creates mutual trust
	Clinician's devotion to involve patient	To the utmost	Clinician should try to involve patient to the utmost
		Within reason	Clinician should try to involve patient within reason
		Respect patient's wish	Clinician should respect patient's wish not to participate
	Manner in which		Clinician gives information; clinician reassures the patient; clinician takes time; clinician involves significant others of patient; clinician gains patient's trust
4. In deciding about treatment, one looks at advantages and disadvantages of various options, among other things. Do you think that physicians are always able to determine how these advantages and disadvantages weigh for a patient? e
5. If the decision is about quality vs length of life, do you think that physicians can always decide for patients how these should be weighed?
	Yes, the starting point is the…	Patient	Patient trusts the clinician; patient does not understand the situation well enough
		Clinician	Clinician has the expertise; clinician is responsible; clinician has the ability to estimate patient values
		Patient-clinician relationship	Good communication; clinician knows the patient well enough
	No, the starting point is the …	Patient	Individual patients differ too much from one another; patient makes own decision; patient knows best; patientś experience with health or health care differ; patients differ in their acceptance of treatments
		Clinician	Clinician has own subjective stance; clinician cannot infer importance for patient; clinician brings in own emotions
		Patient-clinician relationship	Clinician does not know patient well enough; clinician and patient need to consult together; patient needs to share own values with clinician

^aThe participants' explanations to this question were only coded in those agreeing to patient involvement.

^bThe participants' explanations to this question were only coded in those agreeing to patient involvement (question 1) and disagreeing to question 2.

^cThis category includes references to psychological inabilities in patients that participants did not further specify.

^dThe participants' explanations to this question were coded both in those answering ‘yes’ and ‘no’ to the question.

^eCoding categories for questions 4 and 5 were identical.