Participants in the eConquerFear-HK intervention group will receive six online modules with each containing educational text, illustrative graphics, interactive exercises, and brief videos. Every module will teach a specific topic, such as self-examination and medical surveillance, values-based goal setting, attention training, detached mindfulness, worry management and treatment summary and relapse prevention.

Participants in the control group will receive six videos, which were designed to provide comprehensive lifestyle guidance (e.g., relaxation techniques, diet and physical activity advices) to help with survivors' maintenance of health in long-term.

The key goals of the intervention are to: (i) teach strategies for controlling worry and excessive threat monitoring; (ii) modify underlying unhelpful MCQ beliefs about worry; (iii) develop appropriate monitoring and screening behaviours, (iv) encourage acceptance of the uncertainty brought about by a cancer diagnosis, and (v) clarify values and encourage engagement in values-based goal setting.

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).