Table 1.

Description of the measures and their psychometric properties, scoring, and interpretation.

Outcome	Instrument	Scoring and interpretation
Level of decisional conflict	Decision Conflict Scale	The German version of the Decision Conflict Scale demonstrated good psychometric properties. The internal consistency was found to be high (Cronbach=.96). It has 5 subscales with a total of 16 items and 5 response categories, ranging from 0 (strongly agree) to 4 (strongly disagree). The total score is calculated in the following way: The 16 Items are (1) summed, (2) divided by 16, and (3) multiplied by 25. Scores range from 0, no decisional conflict, to 100, extremely high decisional conflict.
Patients' involvement in decision making	Questionnaire for participatory decision making (PEF-FB-9)	The German questionnaire on shared decision making “Der Fragebogen zur Partizipativen Entscheidungsfindung” (PEF-FB-9) demonstrated high internal consistency (Cronbach=.93). It has 9 items scored on a 6-point Likert scale, ranging from 0 (not at all) to 6 (fully correct). The score is created by adding all items (range 0-45 points). A higher score means more shared decision making.
Trade-off between patients' preferences for quality and length of life	Quality-Quantity Questionnaire	The validated German version of the Quality-Quantity Questionnaire consists of 9 items in 2 preference dimensions: Q(uality) of life (QL) and L(ength) of life (LL). The scales demonstrated good and acceptable internal consistency (Cronbach=0.71 for LL and .59 for QL). Patients indicate how strongly they agree or disagree with the statements on a 5-point Likert scale. High scores on the quantity or quality scale indicate the importance of the length or quality of life, respectively.
Preferred role of the patient in decision making	Control Preference Scale (CPS)	The preferred role of the patient in decision making will be assessed with the German version of the CPS. It is a valid and reliable measure of preferred roles in medical decision making. It consists of 5 statements (A, B, C, D, E) that each portrays a different role in treatment decision making. For analysis, a categorical variable, which is the person's most preferred role in treatment decision making, will be created. Preference orders will be reclassified into Active (A, B), Collaborative (C), and Passive (D, E).
Satisfaction with the oncologist-patient interaction	Quality of Physician-Patient Interaction (QQPPI)	The German version of the validated QQPPI — “Fragebogen zur Arzt-Patienten-Interaktion” (FAPI) — showed very good reliability (Cronbach=.97). It has 14 items rated on a 5-point scale (range: 1 [I do not agree] to 5 [I fully agree]). The total score is calculated as a mean of all 14 items. The lowest score (1) indicates the lowest quality of physician-patient interaction, and the highest (14) indicates the highest quality of physician-patient interaction.
Effect on hope	German version of the Herth Hope Index (HHI-D)	The HHI-D has satisfactory reliability (Cronbach=.82). It has 12 items rated on a 4-point Likert scale that ranges from 1 (strongly disagree) to 4 (strongly agree), with items #3 and #6 reverse-coded. The scale has 1 global score that ranges from 12 to 48. Higher scores indicate more hope.
Effect on patients' quality of life	EORTC QLQ-C30	The EORTC QLQ-C30 questionnaire is widely used to measure the quality of life of cancer patients. The QLQ-C30 has a global health status scale, 5 functional scales, and 3 symptom scales. High scores on the functional scales mean healthy functioning. A high score for global health status means a higher quality of life. A high score on the symptom scales indicates a high level of problems. Scores for all scales and single items range from 0 to 100. The questionnaires will be interpreted following the official guidelines of the EORTC.
Effect on patients’ anxiety	Anxiety EQ-5D-5L	The EQ-5D-5L, a preference-based measure of general health status, consists of 5 dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each with 5 levels of problems: 1=no, 2=slight, 3=moderate, 4=severe, and 5=extreme or unable to perform the task. The anxiety/depression dimension of the EQ-5D-5L will be used to detect anxiety and depressive symptoms.