Cognitive therapy has been shown to reduce fear of cancer recurrence (FCR), mainly in breast cancer survivors. The accessibility of cognitive behavioural interventions could be further improved by Internet delivery, but self-guided interventions have shown limited efficacy. The aim of this study is to test the efficacy of a therapist guided internet-delivered intervention (TG-iConquerFear) vs. augmented treatment as usual (aTAU) in Danish colorectal cancer survivors.

Colorectal cancer (CRC) screening, early detection, and improved treatment have led to rising survival rates over the past decades. This improvement has resulted in an increasing number of long-term CRC survivors with no residual disease. Most survivors manage to establish a 'new normal' after finishing treatment, but some survivors experience difficulties in normal functioning and decreased quality of life (QoL) due to substantial psychological strain. Anxiety and depression e.g. are reported in 34% of CRC survivors 1-5 years post-diagnosis. One of the most common concerns among cancer survivors is fear of cancer recurrence (FCR), defined as "Fear, worry or concern relating to the possibility that cancer will come back or progress". The severity of self-reported FCR does not seem to differ much according to cancer type and FCR can persist even among very long term survivors. Higher FCR is associated with multiple psychological factors including (health) anxiety, depression, greater uncertainty in illness, perceived risk of recurrence and negative beliefs about worry. An expert consensus on the defining features of clinical FCR suggested, that the following four features are key characteristics of clinical FCR: a) high levels of preoccupation; b) high levels of worry; c) that are persistent; and d) hypervigilance to bodily symptom.

Most CRC survivors report some degree of FCR. The term "clinically significant FCR" is introduced to describe when the strain of FCR becomes clinically important, negatively influencing the life of the survivor. Validated screening questionnaires, such as the Fear of Cancer Recurrence Inventory-Short Form (FCRI-SF), have been used to identify likely cases of clinically significant FCR. Two recent studies report likely clinically significant FCR based on the FCRI-SF among 13,7% and 10,1% of CRC survivors (unpublished data, personal communication with first authors). However, the prevalence of clinical FCR in CRC survivors is still somewhat uncertain, as estimates are based on small studies [n=51-91], or studies with simplistic or unvalidated FCR measures.

Two large cohort studies have focused on patient reported health-related QoL after (colorectal) cancer. The English study includes people "living with and beyond cancer", which does not distinguish between survivors with no residual disease, those living with cancer or with a history of recurrence. Furthermore, FCR is assessed with a single item. A Dutch study based on the PROFILES registry used the Impact of Cancer scale (Health Worries subscale) measure, which does not include a proposed cut-off score for clinical FCR. The current study will provide a more definitive estimate of the prevalence of clinical FCR in CRC survivors.

This study will also explore psychological factors related to FCR in CRC survivors. A cancer diagnosis is life changing and imposes heavy stress on patient and relatives. Together with often numerous physical symptoms and social changes after the cancer treatment, the net sum of stressors may exceed the cancer survivor's ability to adapt. This overload may manifest in the experience of bodily symptoms and in some cases develop into a functional disorder/somatic symptom disorder such as bodily distress syndrome or health anxiety, as proposed by Simonelli et al. Bodily distress syndrome is defined as a condition in which the patient suffers from, usually multiple, bodily symptoms in a characteristic pattern not attributable to verifiable, conventionally defined diseases.

Health anxiety is characterized by preoccupation with fear of having a serious and life-threatening illness with no objective sign of disease, which persists despite medical reassurance. Health anxiety and FCR overlap somewhat, as they both include unpleasant thoughts or ruminations, which interfere with everyday life and may lead to further unnecessary investigations and treatments. One study investigated hypochondriasis in breast cancer survivors and found that 43% of those with a clinical level of FCR met the diagnostic criteria. Two studies of one CRC cohort have measured somatization (i.e. manifestation of physiological distress as physical symptoms), but not links with FCR. To the best of our knowledge, no previous studies have investigated the relationship between functional disorders, FCR, anxiety and depression in CRC survivors.

Illness uncertainty has been linked with FCR and health anxiety. When diagnosed asymptomatic through screening, illness uncertainty might by heightened. Therefore, diagnosis via screening may lead to increased issues in coping with the cancer and FCR. The comprehensive Danish Clinical Cancer Registries contain data on the method of diagnosis, namely whether the CRC survivor was diagnosed through the Danish nationwide Colorectal Cancer Screening Program, as opposed to diagnosed as a result of symptoms. This enables research in this unexplored area of psychosocial consequences of screen-detected cancers.

Around one fourth (26,5%) of CRC survivors and 20-56% of people living with and beyond CRC report psychosocial assistance in coping with FCR to be an important unmet need. Randomized controlled trials testing interventions for reducing FCR have primarily been conducted in breast or mixed cancer survivor populations. Most interventions are based on variations of cognitive-behavioural therapy (CBT). Contemporary CBTs aiming to modify cognitive processes (e.g., attentional bias and beliefs about worry) rather than thought content (e.g. thoughts of death) were more effective (g=0.42 vs 0.24). The delivery format of interventions previously or currently being evaluated has been group, face-to-face, blended, by telephone or by web-based platforms.

"ConquerFear" is an individual face-to-face therapist-delivered intervention with demonstrated efficacy in reducing FCR compared to a relaxation training attention control group of patients with mixed cancers of whom the majority (89%) were women with breast cancer. While use of ConquerFear has been sustained by many study therapists beyond the end of the study, it is a resource and time-consuming approach accessible primarily to those in close proximity to major metropolitan cancer centres with highly trained psychologists. Consequently, a web-based self-management version of ConquerFear has been created (iConquerFear), similar in curriculum content but different in delivery. Qualitative evaluation of the usability of iConquerFear showed: iConquerFear was normalising and empowering; flexible access was key; delivery mode was engaging; tailoring was crucial; links to additional resources were valued.

Web-based interventions have the potential to fill an important gap in quality cancer care by augmenting limited available mental health services. However, there is some evidence that entirely self-guided web-based FCR interventions may have limited efficacy, and it has been suggested that therapist input may increase efficacy. Web-based therapist-guided cognitive therapy has advantages for both patients and providers and effects appear comparable to traditional face-to-face therapy in treating distress in patients with cancer. Evidence suggests that guided web-based interventions are superior to unguided interventions.

Aim The primary aim of this RCT is to test if a therapist-guided version of iConquerFear (TG-iConquerFear) can reduce FCR and improve QoL for CRC survivors more than augmented treatment as usual (aTAU).

Secondary objectives are to i) outline the prevalence of FCR in a population based CRC cohort up to 5 years post-diagnosis using a validated FCR measure with a clinical cut-off. This comprehensive screening will also be used to recruit to the RCT of TG-iConquerFear.

ii) outline the prevalence of anxiety, depression, bodily distress syndrome and health anxiety in a population based CRC cohort up to 5 years post-diagnosis.

iii) investigate whether being diagnosed as a consequence of the Danish Nation-wide Colorectal Cancer Screening Program increases FCR compared to being diagnosed based on physical symptoms and whether this relationship is mediated by increased uncertainty in illness.

iv) investigate whether FCR is associated with anxiety, depression, bodily distress syndrome and health anxiety in CRC survivors, as well as investigate whether uncertainty in illness, negative beliefs about worry and perceived risk of cancer recurrence act as moderators or mediators of these relationships.

v) examine the cost-effectiveness of the TG-iConquerFear intervention versus aTAU.

Inclusion Criteria:

• Completed curative intent colorectal cancer treatment with surgery and/or radiation and/or adjuvant chemotherapy between 1 March 2014 and 31 December 2018
• No history of recurrence after primary operation
• Fear of Cancer Recurrence Inventory score of 22 or above (14)
• Age 18 or above
• Reads and understands Danish
• Access and ability to use Internet

Exclusion Criteria:

• Cancer recurrence at any follow-up
• Inability to comply with the protocol due to severe psychiatric, cognitive disorder or substance abuse identified during telephone interview
• As the intervention is web-based, participants without knowledge of or access to the Internet will be excluded from the RCT (including dyslexia).

Data will be available up on request