E-intervention on Subclinical Fear of Cancer Recurrence

number of participants consent and being randomized/number of eligible patients x 100

number of participants who complete follow-up assessments at 3 and 6 months post-baseline/number of participants enrolled x 100

number of participants who complete the intervention/number of being allocated to attend the intervention x 100

Intervention utility will be assessed using the site use metrics, including total number of log-ins

Acceptability of the intervention will be assessed using the 22-item measure, which was adopted from the 31-item measure designed to assess the general views on the presentation and content of information in a decision aid intervention for treatment decision making. It assess the comprehensibility of the intervention content and also its utility using 4- (1 = "Poor"; 2 = "Fair"; 3 = "Good"; 4 = "Excellent") or 5-option (1 ="strongly disagree"; 5 = "strongly agree") categorical responses, respectively. Higher scores indicate better acceptability.

Fear of cancer recurrence. FCR will be assessed using the Chinese 42-item Fear of Cancer Recurrence Inventory (FCRI) at four assessment points (T0-T3).(5) FCRI comprises seven subscales: trigger, severity, psychological distress, functional impairment, reassurance, insights and coping strategies measured using 5-point Likert scales (0 = "never"; 4 = " a great deal or all the time").(5) Total scores range from 0 to 168; with higher scores indicating higher FCR.

Quality of life will be measured by the Chinese version of the 30-item European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire (EORTC QLQ-C30), consisting of five functional subscales (physical, role, emotional, cognitive, and social functioning), three symptom subscales (pain, fatigue and nausea/vomiting), a global health subscale, five single symptom items (e.g., sleep disturbance, dyspnea, appetite loss, constipation, and diarrhea), and an single item for financial difficulty. The score range is 0-100. High scores on the functional and global health subscales indicate better functioning and QoL, respectively. High scores on the symptom subscale or item indicate more symptom(s).

e Chinese 14-item Hospital Anxiety and Depression Scale (HADS),(21) comprising two 7-item subscales that measure anxiety and depression. Each subscale total scores range from 0 to 21 with higher scores suggesting higher distress.

Attitude towards internet will be assessed using a 6 points-categorical Likert scale (0-5) asking if they find internet easy to use. Higher scores indicate more positive attitude towards internet.

A 17-item treatment satisfaction questionnaire, originally designed to evaluate overall satisfaction with the intervention in our current RCT of ConquerFear-HK, will be used. The first 9 items will be assessed using a 5 points-categorical Likert scale (1-5) Higher scores indicate higher satisfaction. The remaining questions are open-questions.

Metacognition will be assessed at T0-T3 using the 30-item Metacognitions Questionnaire- 30 (MCQ-30), consisting of five subscales assessing Positive beliefs about worry, Negative beliefs about worry, Cognitive Self-Consciousness, Cognitive Confidence, and Need to control thoughts. A 4 points-categorical Likert scale (1-4) will be used. Higher scores indicate worse metacognition