Internet-Delivered Psychological Treatment for Cancer Survivors

General Anxiety Disorder 7 (GAD-7, theoretical range: 0-21, where a higher score indicates more general anxiety). The phrasing is revised to concern the past week. The conventional version is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

Patient Health Questionnaire 9 (PHQ-9, theoretical range: 0-27, where a higher score indicates more symptoms of depression). The phrasing is revised to concern the past week. The conventional version is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

9-item Fear of Cancer Recurrence Inventory (FCRI-9, theoretical range: 0-36, where a higher score indicates a more pronounced fear of cancer recurrence). This scale is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

14-item Health Anxiety Inventory (HAI-14, theoretical range: 0-42, where a higher score indicates more health anxiety). This scale is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

Somatic Symptom Scale 8 (SSS-8, theoretical range: 0-32, where a higher score indicates a higher somatic symptom burden). Exploratory secondary analyses will be based on individual items, each scored 0-4. This scale is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

Body Image Scale (BIS, theoretical range: 0-30, where a higher score indicates a higher level of body image distress)

12-item World Health Organization Disability Assessment Schedule 2.0 (WD2-12, theoretical range: 0-100, where a higher score indicates more disability). This scale is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

Credibility/Expectancy scale (C/E scale, theoretical range: 0-50, where a higher score indicates higher credibility/expectancy)

Working Alliance Inventory (WAI, theoretical range: 6-42, where a higher score indicates a stronger therapeutic alliance)

8-item Client satisfaction questionnaire (CSQ-8, theoretical range: 8-32, where a higher score indicates higher satisfaction with treatment)

Brief questionnaire with three free-text items, each of which can be used to report an adverse event. For each adverse event, a rating is given of initial negative impact, and negative impact at post-treatment, on a scale from 0: "not at all", to 3: "very negatively". Reported primarily in terms of the number of participants reporting at least one adverse event.

20-item Negative Effects Questionnaire (NEQ-20). This will be reported as the proportion of endorsed items in the following subdomains: increase in symptoms, perceived insufficient quality of treatment, dependency, stigma, and hopelessness.

Lifestyle Behaviors Questionnaire (LBQ). The LBQ comprises 11 items that cover tobacco use, alcohol use, physical activity and diet. Dichotomous risky lifestyle behavior variables will be derived from the LBQ in terms of: "At least one unhealthy lifestyle behavior", "Daily smoking", "Binge drinking more than once a month OR more than 9/14 (w/m) glasses/week", "Insufficient physical activity, less than 150 minutes/week", and "Notably unhealthy dietary habits (diet index 0-4)". Risky lifestyle behavior will be defined as daily smoking, binge drinking of 4/5 (women/men) drinks at one occasion more than once a month and/or more than 9/14 (women/men) standard glasses of alcohol weekly, insufficient physical activity (<150 minutes/week) or significantly unhealthy diet habits (a score of 0-4 on a diet index in the questionnaire, ranging from 0-12).

3-item Behavioral Activation for Depression Scale - ACtivation subscale (BADS-AC-3, theoretical range: 0-18, where a higher score indicates a higher level of behavioral activation). This scale is also administered at screening (within 6 months before treatment), used to inform the eligibility assessment and to describe the sample.

Symptom Preoccupation Scale (preliminary scale). A higher score indicates higher degree of preoccupation with symptoms. This is to be regarded as an an item pool, and the scale is is under development, which means that the total range cannot be preregistered.

Godin-Shephard Leisure-Time Physical Activity Questionnaire (GSLTPAQ, theoretical range 0-99, where a higher score indicates a higher level of physical activity). If necessary for statistical modeling, the GSLTPAQ will be dichotomized to indicate active (≥24) vs. insufficiently active (<24).

Based loosely on the Arthritis Self-efficacy Scale. Theoretical range of 0-60, where a higher score indicates a higher level of general health-related self-efficacy.

EuroQol 5D (EQ-5D). Theoretical range: 0-1, i.e., scored as utility for the purpose of calculating quality-adjusted life years for health economic analysis. A higher utility score indicates a higher health-related quality of life.

Trimbos Institute and Institute of Medical Technology Questionnaire for Costs Associated with Psychiatric Illness (TIC-P). This instrument is scored in terms of resource use for the purpose of calculating societal costs for health economic analysis.

Health Anxiety Behavior Inventory (HABI, scored as four subscales of "bodily preoccupation and checking", "information- and reassurance-seeking", "prevention and planning" and "overt avoidance"; each with a theoretical range of 0-9 where a higher score indicates a higher level of health anxiety behaviors within each respective subdomain)

Alcohol Use Disorders Identification Test (AUDIT, theoretical range: 0-40, where a higher score indicates more problematic alcohol use). This scale is administered to inform the eligibility assessment and describe the sample only.

Drug Use Disorders Identification Test (DUDIT, theoretical range: 0-44, where a higher score indicates more problematic substance use). This scale is administered to inform the eligibility assessment and describe the sample only.