OBJECTIVES: The responsibility of caring for cancer patients, often suffering from a magnitude of health problems, can result in a considerable burden for their caregivers, both physically and psychologically. The objective of this study was to assess the status and extent of clinical research into the burden of caregiving for cancer patients. METHODS: ClinicalTrials.gov was searched for all cancer trials that considered caregiver burden, using a matrix of search terms such as ‘carer’, ‘burden of care’ or ‘caregiver’. The impact of geographical location or cancer type on the proportion of trials assessing caregiver burden, the outcome measures used and the proportion of trials including caregiver burden as an outcome over time were investigated. RESULTS: From a total of 36,184 cancer-focused trials documented worldwide, 1,596 (4%) assessed caregiver burden. Outcome measures included caregiver quality of life (QoL), satisfaction with care and mood states. The impact of caregiver burden in cancer trials within different world regions varied, with the highest proportion of trials that considered caregiver burden located in Mexico (23%) and Asia (14-22%). Trials for five major cancer types (breast, lung, prostate, colorectal, liver) assessed caregiver burden at similar frequency (4-5%). Evaluation of completed trials demonstrated that the proportion of cancer trials considering caregiver burden increased from <1% between 1997-2001 to 7% after 2012. CONCLUSIONS: Fewer than 5% of all cancer trials documented worldwide have evaluated the impact of caregiver burden, although geographical variation does exist. The equal assessment of caregiver burden across cancer types may suggest that no single cancer type is considered to have a higher degree of caregiver burden. Interestingly, while the number of total cancer trials evaluating caregiver burden documented to date is relatively low, the incidence has increased over the last 15 years, suggesting that the growing importance of caregiver burden is being recognised.