 Statistical analyses Baseline characteristics will be compared between the intervention and control group using descriptive statistics. Chi square tests will be used for categorical variables. Independent sample T-tests and Mann-Whitney U-tests will be used for continuous variables, according to the variable distribution. Change in CAT-score, respiratory parameters and 6MWD between baseline and four weeks will be compared between patients in the intervention and the control group. First, mean change in CAT-score, respiratory parameters and 6MWD will be compared between the two groups using an independent sample T-test or Mann-Whitney U test, according to the variable distribution. Afterwards, multivariate analyses for longitudinal data will be performed. Analyses will be done using an intention-to-treat approach. The relationship between response to opioids and severity of dyspnea and descriptors of breathlessness will be explored using univariate analysis, followed by a binary logistic regression model. A trial-based economic evaluation will be performed, based on empirical data obtained in the RCT. The economic evaluation will be performed from the societal and healthcare perspective, the first including costs inside and outside the health care sector, and will follow published international guidelines. The time horizon of the trial-based economic evaluation will be four weeks. The outcomes of the twelve weeks following the intervention will be used in the model-based economic evaluation. The model will probably take the form of a Markov model; however this will be decided upon during the study. 