Breast Cancer Drug Side Effects Worse in Women with Negative Expectations

Breast cancer patients who expected significant side effects from adjuvant hormone therapy reported worse adverse events.

Women with breast cancer who expected the worst from adjuvant hormone therapy experienced an increase in side effects, according to a study published in the Annals of Oncology.

The findings are significant, because if expectations can predict the risk of experiencing side effects, then certain interventions could lower the risk, and result in the improvement of medication adherence.

For the study, researchers used 111 women enrolled in a clinical trial at the Breast Cancer Centre in Germany who had undergone surgery for hormone receptor positive breast cancer, and were scheduled to begin adjuvant hormone therapy with tamoxifen or aromatase inhibitors, such as exemestane.

Each patient was questioned at the start of the trial on their expectations of the effect of taking adjuvant hormone therapy, followed by an assessment at 3 months in 107 women, and at 2 years in 88 women. Researchers found that at the start of the study, 9 patients said they expected no side effects from the treatment, while 70 patients expected mild side effects, and 32 expected moderate-to-severe side effects.

After 3 months, the results of the study showed that 19 patients who later dropped out of the trial reported significantly more side effects than 88 patients who remained. By the end of the 2 years, adherence to medication was associated with side effects at 3 months, along with expectations at the start of the trial.

In fact, 2-year adherence rates were found to be higher in women with low expectations of side effects before treatment began (87%), compared with women who had high expectations of side effects (69%). Furthermore, higher expectations of side effects at the beginning of the study predicted a 1.8% increase in occurrence after 2 years, and lower health-related quality of life compared with women who expected no or mild side effects.

After the findings were adjusted for factors such as sociodemographic, medical, previous menopausal symptoms, and symptoms women already experienced at the start of the study, the expectations still remained as independent and clinically relevant factors.

“Our results show that expectations constitute a clinically relevant factor that influences the long-term outcome of hormone therapy,” said lead researcher Yvonne Nestoriuc. “Expectations can be modified so as to decrease the burden of long-term side effects and optimize adherence to preventive anti-cancer treatments in breast cancer survivors.”

Some of the side effects experienced in the study included joint pain, weight gain, and hot flashes. However, there were some participants who reported symptoms that were not directly attributable to the medication which included back pain, breathing problems, and dizziness.

“This substantiates the conclusion that psychological mechanisms such as negative expectations about the treatment play a significant role in the side effects breast cancer patients experience,” Nestoriuc said. “Higher negative expectations, formed by patients before the start of their adjuvant therapy, seem to have a pronounced influence a long-term tolerability, especially once they are confirmed by initially high side effects after 3 months.”

Authors noted a limitation to the study was that almost 40% of patients who were eligible to join the trial did not do so, and their decision may have been affected by potentially already having negative expectations about adjuvant hormone therapy.

As of now, researchers are conducting a randomized controlled trial to determine whether strategies for improving expectations are effective or not. According to the authors, this includes counseling from psychologists or trained medical staff right before the start of treatment and during the first couple of months, information on treatment that highlights its benefits, explaining possible effects of expectations, and giving patients strategies for coping with these side effects.