Here is the design of a clinical trial:

Official Title: Effect of Perioperative Cognitive Behavioural Therapy on Chronic Persistent Postsurgical Pain Among Breast Cancer Patients With High Pain Catastrophising Characteristics: A Randomised, Double-blind Clinical Trial

Included conditions:
- Breast Cancer
- Chronic Pain
- Chronic Postsurgical Pain
- Quality of Life

Study Armgroups:
- {'label': 'Cognitive Behavioural Therapy (CBT)', 'type': 'ACTIVE_COMPARATOR', 'description': "Cognitive behavioural therapy (CBT) is a talking therapy that can help patients manage problems by changing the way they think and behave. It's most commonly used to treat anxiety, depression and chronic pain conditions.", 'interventionNames': ['Behavioral: Cognitive Behavioural Therapy (CBT)']}
- {'label': 'Education and Mindfulness', 'type': 'PLACEBO_COMPARATOR', 'description': 'Education and mindfulness therapy refers to lessons on techniques to calm the mind and body - can reduce the negative effects of stress', 'interventionNames': ['Behavioral: Education and Mindfulness']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Cognitive Behavioural Therapy (CBT)', 'description': 'The CBT intervention will be delivered by a Senior Psychologist with seventeen years of hospital psychology experience, six in the treatment of chronic pain patients. Sessions are delivered in one hour, individual therapy appointments to patients, and there is an emphasis on relaxation training, cognitive restructuring, exercise and pacing, behavioral activation, improving sleep, and anger management. Standardized worksheets and homework assignments are an important part of CBT-CP and these will be given (post or email) to patients who will be asked to read and complete in terms of complementing the consultations. This intervention has been developed with reference to two sources: A successful national implementation of CBT for chronic pain (CBT-CP) using video teleconferencing format \\[Connolly KS et al\\] AND an evidence-based CBT manual specifically designed to treat chronic pain \\[Murphy JL et al\\].', 'armGroupLabels': ['Cognitive Behavioural Therapy (CBT)']}
- {'type': 'BEHAVIORAL', 'name': 'Education and Mindfulness', 'description': 'To control for differences in attention between the two interventions, patients in the mindfulness group will also have two meetings before the surgery and two meetings afterward. As the same person will be providing the CBT-CP and educational interventions, this confounding factor will be controlled for. The control intervention consists of discussing pain education, as derived from the self-management section of the chronic pain Ireland website (https://www.chronicpain.ie/our-services/self-management) and the persistent pain section of the pain toolkit website (https://www.paintoolkit.org/persistent-pain). Four mindfulness-based stress reduction exercises will be completed including an introductory session on mindful breathing, a guided meditation, progressive muscle relaxation, and a body scan. These sessions will last about half an hour.', 'armGroupLabels': ['Education and Mindfulness']}

Primary Outcomes:
- {'measure': 'Brief Pain Inventory (BPI) Short-form: average pain severity', 'description': "BPI Short-form is a 9 item questionnaire used to evaluate the severity of a patient's cancer or non cancer pain \\[Tan G et al\\]. Brief Pain Inventory short-form scale is measured between 0 - 10, where '0' indicates no pain and '10' indicates severe pain. A decrease in the Brief Pain Inventory score of 2 or more from the baseline score is considered significant and indicates an improvement in severity of the patient's cancer and non-cancer pain.", 'timeFrame': '3 months post-operative'}

Please estimate the sample size based on the assumption: 
Type I error = 0.05, Type II error = 0.2 (power 80%), and a dropout rate of approximately 10%.
Sample size {14}
        The primary outcome is the difference in the BPI average pain severity score between the study groups, three months after surgery. A clinically important difference on the BPI is 2 raw score reduction on the 11-point Numerical Pain Rating Scale (NRS) [22â24]. The standard deviation (SD) of BPI scores after breast surgery is in the order of 2.3 [25] on this scale. Taking a BPI score reduction of 2 as the minimal clinically relevant difference, then n = 21 patients would be required each arm if type I error = 0.05 and type II error is 0.2 (power 80%). This calculation was verified by using an online power calculator (https://www.sealedenvelope.com/power/continuous-superiority/). The screening process for potential eligible participants will be a very thorough methodological process. As mentioned in the exclusion criteria, any suspected non-compliant participants will not be enrolled or randomised to either of the studyâs intervention. By taking this approach, we endeavour to limit the number of dropouts to approximately 10%, and therefore, we propose to enrol 24 eligible patients in each group (N = 48 total).