To understand participant experience in the INTERLINK-1 clinical trial using the Study Participant Feedback Questionnaire (SPFQ), explore factors associated with participant experience and evaluate the implementation of the SPFQ.

Phase 3, randomised, double-blind, placebo-controlled, multicentre trial.

79 sites in 21 countries from October 2020 to October 2022.

371 adults with recurrent/metastatic head and neck squamous cell carcinoma (39% aged >66 years, 69% White and 81% male).

SPFQ administered at enrolment (SPFQ-A), during the trial (SPFQ-B) and at trial completion (SPFQ-C).

A total of 223, 64 and 93 participants completed the SPFQ-A, SPFQ-B and SPFQ-C, respectively. Early termination of the INTERLINK-1 study limited the number of SPFQ-B and SPFQ-C responses. For all but one question, over 80% of participants selected positive responses, indicating positive experience with regards to enrolment (SPFQ-A), site (SPFQ-B) and overall trial (SPFQ-C). Individually, quality of life, continent and race were significantly associated with participant experience. Small numbers of negative and neutral responses enabled the construction of multiple ordinal regression models and were used to identify unbiased coefficients associated with patient experience. The models showed that males and participants in Asia reported worse experiences in questions regarding trial enrolment (p

Overall, participants reported positive experiences in the INTERLINK-1 study as evaluated by the SPFQ. Specific aspects of participant experience varied by sex, continent, recent adverse events and ECOG status. Further investigation is required to understand the causes of these findings to develop strategies for improved participant experience. Observations from this study will be used to inform future SPFQ implementation and develop strategies for better, more equitable trial experiences.

ClinicalTrials.gov: NCT04590963.