Nausea and vomiting (NV) continue to be troublesome and common side-effects of many chemotherapy regimens.
1–5 Although the occurrence and severity of chemotherapy-induced NV derive largely from the emetogenic potential of the chemotherapeutic drugs, individual patient characteristics, such as younger age,
6 female gender,
7 previous experience of pregnancy-related nausea,
6,8 and a history of motion sickness,
9 play a role. Even taking all these factors into account, there is great deal of variability both across and within specific chemotherapyregimens with respect to the occurrence and severity of NV. This unexplained variation in NV might reflect differences in multiple factors, including: the prescription and usage of antiemetic agents,
10 psychological factors, such as infusion-related state anxiety, behavioral conditioning, and general” psychological stress.”
9,11 Patients' beliefs and expectations about whether they will experience NV from chemotherapy have also been demonstrated to be strong and independent predictors of chemotherapy-related NV.
9,12–16In our previous studies, we found a significant relationship between patients’ pretreatment expectations for nausea development and their mean postchemotherapy nausea severity
15 and that pretreatment expectations of experiencing chemotherapy-induced nausea make a significant contribution to the development of anticipatory nausea.
17 Recently, we reported that expectancy of nausea assessed in 194 female breast cancer patients before they received their first doxorubicin-based chemotherapy cycle was a strongpredictor of subsequent nausea severity, and in fact, was a stronger predictor than previously reported predictive factors, such as age, nausea during pregnancy, and susceptibility to motion sickness. In that study, expectation of developing nausea as a result of treatment was assessed before treatment by the question: “Before you spoke to your doctor about possible side effects of chemotherapy, what did you think the chances were that you would have severe nausea from your treatments?” The possible responses were “very unlikely,” “unlikely,” “about even chance,” “likely,” and “very likely.” Patients who believed it was “very likely” that they would experience severe nausea from chemotherapy were five times more likely to have severe nausea than fellow patients who thought its occurrence would be “very unlikely.”
16Several hypotheses have been offered to explain the relationship between symptom expectancies and subsequent report of symptoms. T he simplest explanation is that the predictive capacity of expectancies derives from the patient’s prior experience with factors that cause the symptom. For example, by the time most people reach adulthood, they have a fairly good idea of how susceptible they are to nausea and what circumstances are likely to cause it. Cognitive schemas
18 may also be involved in that expectations of symptoms may exacerbate their intensity and/or frequency because, for an individual expecting a symptom such as nausea, an otherwise ambiguous physiological sensation, such as stomach rumbling, is more likely to be interpreted as nausea than when nausea is not expected. Another possible factor involves what might be called a “Self-Fulfilling Prophecy” (SFP) or “nocebo” effect. SFP is a phenomenon by which belief that a future event will occur contribute to that event actually occurring. SFP plays a powerful role in shaping experiences, and, to the extent that it exists, is causal rather than merelypredictive.
19 As suggested by Kirsch, such beliefs about what is going to happen, termed “response expectancies,” can have a direct and unmediated effect on health outcomes.
20 According to this theory, response expectancies for non-volitional outcomes, such as post-surgical pain or post-chemotherapy nausea, are sufficient to cause the expected outcome, and the effect is self-confirming.
Evidence supporting Kirsch’s theory is provided by several studies that have altered patients' expectations and achieved mitigation or prevention of subjective symptoms, such as pain
21,22 and nausea.
23–25 Changes in objectively measured outcomes, including reduction in blood loss during surgery
26 and resumption of normal gastrointestinal activity in the postoperative period,
27 have also been observed. A particularly interesting example of how response expectancies affect chemotherapy-related nausea comes from a large multicenter study conducted by our research group examining the efficacy of acustimulation and acupressure bands as an adjunct to standard antiemetics for nausea control. Seven hundred thirty-nine patients were randomly assigned to three arms: acupressure bands, an acustimulation band, and a no-band control condition. Patients, who were randomized to receive acupressure bands and expected them to be effective, experienced less severe nausea, reported having a higher quality of life (QOL), and also used significantly less antiemetic medication at home compared to those who wore the bands but did not expect them to be effective, and to those in the no band control (
P<0.05). Conversely, patients receiving the acupressure bands who did not expect them to be effective did not perform differently from the control group on any measure. It appears that the beneficial effect of wearing the acupressure bands on symptom management is due, at least in part, to a placebo/expectancy effect.
28The study described herein addresses the question of whether a modest educational intervention designed to reduce patients’ nausea expectancies by dispelling misconceptions about chemotherapy-related nausea and building confidence in the efficacy of their antiemetic drug regimen results in less nausea.