Conducting randomized controlled trials (RCTs) on palliative care is difficult owing to barriers like fragility of the patients’ health status and health care providers’ concerns for patients. However, quality RCTs are required for care improvement.

To investigate the willingness of cancer patients and their relatives to participate in a clinical study on cancer dyspnea and identify feasible clinical study designs for this condition.

A nationwide, cross-sectional, web-based survey was conducted with 206 cancer patients and 206 relatives of cancer patients. Their willingness to participate in clinical studies on cancer dyspnea and factors influencing this willingness were assessed in two scenarios: outpatients receiving anticancer treatment and terminally ill inpatients.

About 23% patients and 23% relatives were willing to participate in clinical trials while 40% and 32%, respectively, were unwilling. Factors related to patient participation were quick and easy trials (outpatient 57%, terminally ill 53%) and oral medication with minimal potential side effects (outpatient 48%). Factors related to unwillingness to participate were placebo-controlled trials (outpatient 51%, terminally ill 50%), disagreements about participation between patients and families (outpatient 49%, terminally ill 49%), and continuous injections (outpatient 61%, terminally ill 47%). Compared to patients, relatives responded more reluctantly, especially for patients in terminal care. Conversely, patients were less reluctant in the terminal setting than the outpatient setting.

Some patients and relatives were reluctant to participate in clinical trials on cancer dyspnea. Thus, trials need to be minimally invasive, quick, and fully explained to and understood by patients and families.

This article describes a survey that investigated the willingness of cancer patients and their relatives to participate in a clinical study on cancer dyspnea. Results indicate that we need to develop a study design that is minimally invasive, relatively quick, and provides sufficient explanation for patients and families.