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Therapist‐led interventions for the treatment of traumatic stress symptoms in cancer survivors: A systematic literature review

Abstract Objective We reviewed the evidence regarding the effectiveness of therapist‐led interventions for reducing symptoms of traumatic stress in cancer survivors. Methods This systematic review was completed in accordance with the guidelines illustrated by Popay and colleagues and the following online databases, PsychInfo, Medline, CINAHL, were searched for peer‐reviewed literature. Further studies were searched through Google Scholar and manually scanning the reference lists of all included studies. The PRISMA guidelines were followed to report results. Results Sixteen studies were identified, their quality varied and the interventions broadly fell into two categories: CBT‐based and non‐CBT interventions. Effect sizes were small to moderate in 12 studies and large in four. Drop‐out rates were mostly low. Conclusion This review has demonstrated that the research in this field is still scarce and due to the data mostly suggesting a small to moderate effect, firm conclusions cannot be drawn on the effectiveness of the included interventions.

were adjusted to include diagnoses and life-threatening illness such as cancer; this change was made after multiple studies had demonstrated the presence of traumatic stress-like symptoms in cancer patients. 6 However, this adjustment was then revoked in the fifth edition of the DSM 7 ; a life-threatening condition was not considered traumatic anymore unless experienced by the person as sudden and catastrophic.
Unlike other traumatic experiences (e.g., having survived an earthquake) that might lead to individuals developing traumatic stress symptoms, cancer acts as an ongoing and chronic stress for the individual 8 and fear of recurrence is experienced by many cancer survivors. 9,10,11 The Field Trials for the Fourth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-4) 5 found that 22% of cancer survivors suffer from some level of lifetime cancer-related traumatic stress symptoms. 5,6 The most common traumatic stress symptom experienced by cancer survivors include distressing recollections of cancer-related experiences such as receiving a diagnosis and having to undergo invasive procedures (e.g., chemotherapy, radiation, hormonal therapy, etc.). 8,12 In order to avoid triggering distressing recollections which can lead to unpleasant feelings and trauma-related thoughts and images, cancer survivors avoid specific places and situations (e.g., hospitals, doctor appointments, follow-up scans, etc.). 12 Cancer-related traumatic stress symptoms can negatively impact on the ongoing care of cancer patients by reducing attendance at follow-up appointments, and adherence to a healthy lifestyle which may in turn increase healthcare costs and the use of healthcare services in the long run. 13 Although research has demonstrated that cancer survivors want psychosocial support for the emotional and social distress they experience as a result of their cancer journey 6 and are more likely to express their unmet psychological needs in the post-treatment phase compared to other stages in their cancer journey, 14 many cancer survivors are not referred to psychooncology services and therefore are not treated. 15 This is not only caused by an overall lack of psycho-oncologists in national health services, but also by other factors such as poor detection, having to wait long times, and geographical or physical barriers which prevent patients attending appointments. 16 A recent systematic literature review by Dimitrov and colleagues 17 aimed to evaluate the effectiveness of interventions for cancer-related post-traumatic stress; however, the authors excluded papers where participants had not been clearly screened for PTSD or used validated PTSD measures that had subscales that assessed for other symptoms such as depression and overall psychological distress. This inevitably limited the focus of their review (only eight studies were found that matched the review's inclusion criteria). Individuals who do not meet the criterion for PTSD, often display clinically meaningful symptoms which have an impact on their everyday functioning. 18,19, 1 2 Indeed Mundy and Baum 20 stated that PTSD might not be the right diagnosis to represent the emotional and social distress which cancer patients experience; although the PTSD diagnosis may capture many of the traumatic stress symptoms experienced by cancer patients, it may not incorporate the multidimensionality of lasting responses that are typical of the cancer experience. 21,22 Furthermore, Dimitrov and colleagues' work 17 is limited to literature published up to April 2018, and therefore, our review provides with an overview of the most recent literature in the field.
The aim of this review was to systematically review the evidence on the effectiveness of therapist-led psychotherapeutic intervention for reducing symptoms of traumatic stress (e.g., intrusions, hyperarousal, and avoidance) in cancer survivors.

| Search strategy
This systematic review was conducted in accordance with PRISMA guidelines 23  Schema Therapy). The 'n' search term represents the number of words that could appear between keywords/phrases, in our case four; this was used in an attempt to include all cancer types and terminology. These search terms were employed in free-text searches, but where possible, controlled vocabulary indices were also used. Controlled vocabulary indices included neoplasms and survivors, psychological trauma, post-traumatic stress disorder, and psychotherapy. All searches were conducted by the first author (DD).

| Study selection
All citations were managed using the referencing software Mendeley; after all duplicates were removed, the remaining citations' titles and abstracts were screened using the inclusion criteria in Table 1

| Data extraction
The study characteristics that were extracted from eligible studies included: author(s), year, country, total number of participants and their mean age, cancer types, study design, measures of traumatic stress (including times of administration), intervention delivered (including duration and who delivered it), control group (where present), results (including where possible effect sizes). Please refer to Table 2 in Supplemental Appendices for all extracted data.

| Quality appraisal
Due to the heterogeneity of study designs included in this review, the Mixed Method Appraisal Tool (MMAT) 24 was chosen to appraise the quality of the studies selected. The MMAT was developed to help researchers to appraise the methodological quality of empirical studies. Within a single tool, the MMAT provides methodological criteria to appraise five study designs and therefore it is more time efficient compared to other tools. The MMAT can appraise qualitative studies, Randomised Controlled Trials (RCTs), non-randomised trials, quantitative descriptive research, and finally mixed-method study designs; it includes 25 criteria and 2 screening questions. The MMAT is easy to use and access online, comprehensive, quick, and short. 25 Three main steps are followed when using the MMAT. First, there are two optional screening questions which will determine whether the study is empirical or not, then the researcher has to choose the appropriate category for the study they want to appraise so that the MMAT can acknowledge the study's methodological characteristics, and finally, the researcher rates the criteria of the chosen category (e.g., 'Yes', the criterion is met; 'No', the criterion is not met; 'Can't tell', there is not enough information to judge whether the criterion is met or not). Hong and colleagues 21 recommended to provide a thorough presentation of the rating for each criterion when scoring. No study was excluded on the basis of the quality appraisal due to the paucity of studies in this field.

| Data synthesis
Because eligible studies were diverse in terms of their clinical and methodological characteristics (e.g., variability in study design, intervention components, timing of outcome measures), a metaanalysis could not be performed to synthetize the findings. Therefore, a narrative synthesis approach was used to describe and compared eligible studies' characteristics and findings. The narrative

| Quality appraisal
The included studies demonstrated variable quality;

| Effectiveness of cognitive behavioural interventions for traumatic stress in cancer survivors
The majority of studies (62.5%) used CBT 49  promising, the smaller sample size (n = 27) represents a limitation in terms of generalisability. Exposure strategies were also adopted by DuHamel and colleagues, 28 however, although they reported that the intervention was effective, we cannot quantify this as they did not include or provide enough information to calculate effect sizes.

| Effectiveness of non-cognitive behavioural interventions for traumatic stress in cancer survivors
The remaining studies adopted other forms of intervention, such as Positive Psychotherapy (PCC), [36][37][38] Neuro Emotional Technique, 12 Health-Space 33 (live weekly facilitated online chat where cancer-related topics were discussed and coping skills introduced), and Mindfulness-Based Stress Reduction. 41 Effect sizes were found for all studies but one. 37 Large effect sizes were found in study 12,36,38 the remaining interventions had a small to moderate effect size. 33 Two studies delivered PCC, 54 one compared it to a WL control condition 36 and one compared to a + intervention. 38,55 Positive Psychotherapy helps cancer survivors to develop stress

| Acceptability/drop-out rates of interventions for traumatic stress in cancer survivors
Drop-out rates ranged between 0% and 40%. Both case series 12,40 reported 100% attendance, Duhamel et al.

| Review limitations
Studies were limited to English language only and this might have The current review has also only included peer-reviewed papers to ensure a minimum standard for scientific quality at the cost of increasing publication bias: by accessing the grey literature, more studies with a positive results could have been identified. 71 Future systematic literature reviews could consider including the grey literature to widen the search of an already limited field. Finally, this review's protocol was not registered on Prospero a priori and this is acknowledged by the authors as a shortcoming of this paper; however, a search of the Prospero database was conducted before initiating the process to ensure no other systematic literature reviews were conducted on the same topic area.

| Clinical implications
In and beneficial to reduce symptoms of traumatic stress for this population.

ACKNOWLEDGEMENT
No funding was used.