The main study is a two-armed RCT with a 1:1 allocation ratio: (1) online psychosocial intervention; and (2) treat as usual. RCT is a gold standard for examining intervention effectiveness as it is the most reliable approach for proving the causal relationships between interventions and changes in outcome variables. Although no separate study can prove causality, randomization can reduce allocation bias stemmed from the differences in baseline variables and provides a rigorous approach for examining causality between interventions and outcome changes. Therefore, this study adopted an RCT design to examine the effectiveness of the psychosocial intervention in reducing FCR. Primary and secondary outcomes were assessed at two time points: before intervention commencement (T0) and immediate post-intervention (T1). Participants' experience in participating in the intervention was explored at the T1 through individual interview via phone call.~The magnitude of the effects of the intervention on the primary outcome of FCR and other secondary outcomes will be examined to determine if they were consistent with the existing literature. This study hypothesizes that the online psycho-social intervention will yield larger reductions in FCR and other psychosocial outcomes at post-treatment compared with a standardized care control group receiving formal follow-up care including clinical examination and health education on side-effects managements.~Research questions~Question 1: Primary outcome Is the online mindfulness and acceptance intervention effective in the reduction of FCR compared with control condition at post-intervention?~Question 2: Secondary outcomes Is the online mindfulness and acceptance intervention effective in reducing cognitive avoidance, illness representation, and in enhancing quality of life compared with the control condition?~Question 3: Participants' Experience What is the perception of the participants about the impact of the online intervention program on FCR?
A total of 244 breast cancer survivors will be invited to participate in the randomized controlled trial. Breast cancer survivors who meet the inclusion criteria and provide digital informed consent will be included. Participants will be stratified and randomized by the severity of baseline fear of cancer recurrence and time since diagnosis. In the control arm, women will be treated as usual. In the intervention arm, women will be offered a six-weekly, 60 min, online mindfulness and acceptance intervention. An online questionnaire will be used to collect data at four time points: before the first group session, immediately after the intervention, three months, and six months post-intervention. Phone interviews exploring participants' experiences will be held immediately after the intervention with women of the intervention group.