DOSAGE study: protocol for a phase III non-inferiority randomised trial investigating dose-reduced chemotherapy for advanced colorectal cancer in older patients.

introductionTreating older adults with chemotherapy remains a challenge, given their under-representation in clinical trials and the lack of robust treatment guidelines for this population. Moreover, older patients, especially those with frailty, have an increased risk of developing chemotherapy-related toxicity, resulting in a decreased quality of life (QoL), increased hospitalisations and high healthcare costs. Phase II trials have suggested that upfront dose reduction of chemotherapy can reduce toxicity rates while maintaining efficacy, leading to fewer treatment discontinuations and an improved QoL. The DOSAGE aims to show that upfront dose-reduced chemotherapy in older patients with metastatic colorectal cancer is non-inferior to full-dose treatment in terms of progression-free survival (PFS), with adaption of the treatment plan (monotherapy or doublet chemotherapy) based on expected risk of treatment toxicity. METHODS AND ANALYSIS: The DOSAGE study is an investigator-initiated phase III, open-label, non-inferiority, randomised controlled trial in patients aged≥70 years with metastatic colorectal cancer eligible for palliative chemotherapy. Based on toxicity risk, assessed using the Geriatric 8 (G8) tool, patients will be stratified to either doublet chemotherapy (fluoropyrimidine with oxaliplatin) or fluoropyrimidine monotherapy. Patients classified as low risk will be randomised between a fluoropyrimidine plus oxaliplatin in either full-dose or with an upfront dose reduction of 25%. Patients classified as high risk will be randomised between fluoropyrimidine monotherapy in either full-dose or with an upfront dose reduction. In the dose-reduced arm, dose escalation after two cycles is allowed. The primary outcome is PFS. Secondary endpoints include grade≥3 toxicity, QoL, physical functioning, number of treatment cycles, dose reductions, hospital admissions, overall survival, cumulative received dosage and cost-effectiveness. Considering a median PFS of 8 months and non-inferiority margin of 8 weeks, we shall include 587 patients. The study will be enrolled in 36 Dutch Hospitals, with enrolment scheduled to start in July 2024. This study will provide new evidence regarding the effect of dose-reduced chemotherapy on survival and treatment outcomes, as well as the use of the G8 to choose between doublet chemotherapy or monotherapy. Results will contribute to a more individualised approach in older patients with metastatic colorectal cancer, potentially leading to improved QoL while maintaining survival benefits. ETHICS AND DISSEMINATION: This trial has received ethical approval by the ethical committee Leiden Den Haag Delft (P24.018) and will be approved by the Institutional Ethical Committee of the participating institutions. The results will be disseminated in peer-reviewed scientific journals. TRIAL REGISTRATION NUMBER: NCT06275958.