Background: Chemotherapy-induced nausea and vomiting is a common problem in patients undergoing chemotherapy, influencing quality of life (QoL) and daily activities. This study will investigate whether therapists' positive communication may strengthen positive treatment expectations and induce antiemetic effects during antiemetic treatment using standard care, sham acupuncture, or verum acupuncture, compared to neutral communication. It will also investigate whether a variety of patient, therapist and treatment components modify the treatment outcomes.

Methods: This is a trial protocol for a randomized, sham-controlled, patient- and evaluator-blinded clinical trial. Patients (n = 198 patients according to a sample size calculation) with breast, colorectal, or bladder cancer undergoing neo-/adjuvant moderately to highly emetogenic chemotherapy are being randomized in 2 × 3 factorial design to the following conditions: 1. neutral or 2. positive communication style regarding expected treatment effects, during the antiemetic treatment types: A) standard care only (including antiemetics, no acupuncture), or, in addition to standard care, B) sham acupuncture with telescopic non-penetrating needles, or C) verum, penetrating acupuncture. The 2 communication styles 1 and 2 are carried out during the antiemetic treatments given by an intervention therapist immediately pre and post (20 minutes × 2) an intravenous chemotherapy session. Data are being collected at baseline on the day before the chemotherapy session, daily for 10 days, at a 10-day follow-up, and at a follow-up after completing the entire chemotherapy period, lasting about 6 months. Primary outcome is mean score Visual Analog Scale nausea grading for the first 5 days of the chemotherapy session period. Secondary outcomes are for example, vomiting, treatment expectations, QoL, daily and physical activity, and physiological measures. Treatment effect modifiers will be analyzed, for example, blinding success, treatment expectations, and previous nausea experiences.

Conclusions: This trial will expand integrative cancer care's understanding of the effects of communication for strengthening treatment expectations and thus alleviating chemotherapy-induced nausea and vomiting. If proven effective, the communication model of strengthening positive treatment expectations in patients with risk for nausea and vomiting can be implemented in routine clinical care as part of side-effect management for patients with cancer.

Trial registration: US National Institutes of Health, https://clinicaltrials.gov/study/NCT03232541?term=NCT03232541&rank=1), # NCT03232541.