Introduction: Many chemotherapy agents used to treat advanced cancer are inherently mucotoxic, causing breakdown of the gastrointestinal mucosa (gastrointestinal mucositis (GI-M)) and lead to a constellation of secondary complications including diarrhoea, malnutrition, anorexia, pain, fatigue and sleep disturbances. These symptoms are usually managed individually, leading to polypharmacy and its associated risks. The endocannabinoid system regulates numerous biological and behavioural processes associated with chemotherapy side effects, suggesting its modulation could control these symptoms. Therefore, the CANnabinoids in CANcer (CANCAN) therapy trial is a phase II, randomised, double-blind, placebo-controlled trial that aims to determine the efficacy of medicinal cannabis in minimising GI-M and its associated symptom burden.

Methods and analysis: The CANCAN trial is being conducted at four Australian sites: the Royal Adelaide Hospital, the Queen Elizabeth Hospital, Flinders Medical Centre and the Lyell McEwin Hospital. Adults (n=176) diagnosed with a solid tumour or a haematological cancer scheduled to receive mucotoxic chemotherapy will be eligible. Participants will be randomised 1:1 to receive either the investigational product (IP) or placebo, both delivered as sublingual wafers. The active IP contains cannabidiol (300 mg/day) and Δ⁹-tetrahydrocannabinol (5-20 mg/day, titrated by the participant). The primary outcome is GI-M burden, determined by the Mucositis Daily Questionnaire. Secondary and tertiary outcomes include overall symptom burden (Edmonton Symptom Assessment Scale), anorexia (Average Functional Assessment of Anorexia/Cachexia Therapy), depression/anxiety (Hospital Anxiety and Depression Scale), financial toxicity (Functional Assessment of Chronic Illness Therapy COmprehensive Score for financial Toxicity), quality of life (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire), incidence of chemotherapy dose reductions/modifications, cumulative dose of chemotherapy administered, incidence/length of hospitalisation, the use of supportive care, and the cost-benefit of the IP. The CANCAN trial prioritises patient experiences by focusing on patient-reported outcome measures and administering medicinal cannabis during active treatment to prevent symptoms that occur secondary to mucositis.

Ethics and dissemination: The protocol has been approved by Central Adelaide Local Health Network Human Research Ethics Committee (2022HRE00037). All participants will be required to provide written or digitally authorised informed consent. Trial results will be disseminated in peer-reviewed journals, and at scientific conferences.

Trial registration number: ACTRN12622000419763.