Public Preference for Off-Label Use of Drugs for Cancer Treatment and Relative Importance of Associated Adverse...

Patients may get more treatment options with off-label use of drugs while exposed to unknown risks of adverse events. Little is known about the public or demand-side perspective on off-label drug use, which is important to understand how to use off-label treatment and devise financial assistance. This study aimed to quantify public preference for off-label cancer treatment outcomes, process, and costs, and perceived importance of associated adverse events.

A discrete choice experiment and a best-worst scaling were conducted in Hong Kong in December 2022. Quota sampling was used to randomly select the study sample from a territory-wide panel of working-age adults. Preferences and willingness to pay (WTP) for treatment effectiveness, risk of adverse events, mode of drug administration, and availability of off-label treatment guidelines were estimated using a random parameter logit model and latent class model. The relative importance of different adverse events was elicited using Case 1 best-worst scaling.

A total of 435 respondents provided valid responses. In the discrete choice experiment, the respondents indicated that extra overall survival as treatment effectiveness (WTP: HK$448,000/US$57,400 for 12-month vs 3-month extra survival) was the most important attribute for off-label drugs, followed by the risk of adverse events (WTP: HK$318,000/US$40,800 for 10% chance to have adverse event vs 55%), mode of drug administration (WTP: HK$42,000/US$5300 for oral intake vs injection), and availability of guidelines (WTP: HK$31,000/US$4000 for available versus not available). Four groups with distinct preferences were identified, including effectiveness oriented, off-label use refusal, oral intake oriented, and adverse event risk aversion. In the best-worse scaling, hypothyroidism, nausea/vomiting, and arthralgia/joint pain were the three most important adverse events based on the perceptions of respondents. Risk-averse respondents, who were identified from the discrete choice experiment, had different perceived importance of the adverse events compared with those with other preferences.

Knowing the preference and WTP for cancer treatment-related characteristics from a societal perspective facilitates doctors' communications with patients on decision making and treatment goal-setting for off-label treatment, and enables devising financial assistance for related treatments. This study also provides important insight to inform evaluations of public acceptance and information dissemination in drug development as well as future economic evaluations.