Women expecting side effects from taking some breast cancer drugs are more likely to experience them than women with more optimistic expectations.
Researchers discovered that women anticipating adverse effects from adjuvant hormone therapy, such as tamoxifen or exemestane, experienced twice the number of side effects compared with other women who were more positive about the treatment.
The findings, published in Annals of Oncology
(online, 22 August 2016), are significant enough to suggest that women should be offered counselling about adjuvant hormone therapy to potentially reduce side effects and improve adherence, the researchers say.
“Expectations are a genuine factor of clinical outcome from endocrine treatment for breast cancer. Negative expectations increase the risk of treatment-specific side effects, nocebo side effects, and non-adherence … optimising individual expectations might be a promising strategy to improve side effect burden, quality of life, and adherence during longer-term drug intake.”
Researchers recruited 111 women who had undergone surgery for hormone receptor-positive breast cancer and who were scheduled to start adjuvant hormone therapy with tamoxifen or aromatase inhibitors such as exemestane.
The women were quizzed about their expectations of side effects of the drugs at the start of the treatment, at three months and at two years.
Some 8% revealed that they expected no side effects from the drugs, 63% said they expected mild side effects, and 29% expected moderate to severe side effects.
After 24 months of endocrine treatment, patients reported high rates of side effects, such as arthralgia (71.3%), weight gain (53.4 %,) and hot flushes (46.5%).
But the researchers found that pre-treatment expectations “significantly predicted” patient-reported long-term side effects and quality of life.
The relative risk of side effects at 24 months was higher in women with high negative expectations at the start of the trial compared with those with low negative expectations (relative risk = 1.833, confidence interval 95%, 1.032–3.256).
The study also revealed that side effects at 24 months were significantly higher in patients with high side effects at three months compared with those patients with low initial side effects.
Patient expectation of the impact of the treatment influenced drug adherence at two years. At three months, 19 patients who later dropped out of the trial reported “significantly” more side effects at that point than the 88 women who remained long-term.
The research was welcomed by the charity Breast Cancer Now.
Sally Greenbrook, the charity’s policy manager, says the findings reinforce the importance of communication between patients, clinicians and medics “to impart information in a way that doesn’t give women overly negative expectations”.
But she says further investigation is needed to confirm the results of the study because of its small sample size.
“More research would be necessary to confirm whether there really is a link between expectations and experience of side effects of breast cancer treatment. Whether these results hold true or not, the side effects of cancer treatment can have a serious impact on patients’ quality of life and women need support to deal with them.”
 Nestoriuc Y, von Blanckenburg P, Schuricht F et al. Is it best to expect the worst? Influence of patients’ side-effect expectations on endocrine treatment outcome in a 2-year prospective clinical cohort study. Annals of Oncology 2016. doi: 10.1093/annonc/mdw266