The number and severity of side effects that women with breast cancer experience after receiving hormone therapies like tamoxifen are shaped by their expectations. Women expecting to suffer worse and more side effects are found to experience nearly twice as many as counterparts with no particular or positive expectations.

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The study found that women who were expecting their side effects from breast cancer hormone treatment to be bad had nearly twice as many side effects after 2 years of treatment.

These were the main findings of a new German-led study published in the Annals of Oncology.

Study leader Prof. Yvonne Nestoriuc, from the Department of Psychosomatic Medicine and Psychotherapy at the University Medical Centre in Hamburg, Germany, says:

"Our results show that expectations constitute a clinically relevant factor that influences the long-term outcome of hormone therapy."

Such findings are important, she and her colleagues say, because bad experiences of side effects could make women stop taking their hormone treatment, which in turn affects treatment success and survival.

However, if studies like this show expectations can alter the experiences of side effects, then steps can be taken beforehand to lower the risk of having bad side effects and thereby improve chances of keeping to the medication regimen.

Expectations linked to medication adherence

The team studied 111 women participating in a clinical trial at the Breast Cancer Centre at the University of Marburg, Germany.

All the patients had undergone surgery for hormone receptor-positive breast cancer and were due to start adjuvant hormone therapy with tamoxifen or aromatase inhibitors, such as exemestane, when the team first questioned them about their expectations of side effects.

The team then assessed the women again after 3 months (107 women) and then after 2 years (88 women).

At the start of the study, 8 percent (9 individuals) of patients said they did not expect any side effects from their adjuvant hormone treatment, while 63 percent (70) said they were expecting some mild effects, and 29 percent (32) said they were expecting moderate to severe effects.

At the 3-month follow-up, the 19 patients who later dropped out of the trial reported significantly more side effects from the adjuvant hormone therapy than the 88 patients who remained.

At the 2-year follow-up, the researchers found the women's adherence to the therapy - that is, the extent to which they followed their medication schedule - was linked to the side effects they experienced 3 months into the trial, and also to their expectations at the outset.

Specifically, medication adherence at the 2-year point was higher in those women who had expressed low expectations of side effects (87 percent adherence) at the outset than in women with high expectations of side effects (69 percent adherence).

Expecting bad side effects predicted twice as many

Expressed statistically, the results show that the women who expected side effects to be bad had nearly twice as many (1.8 times more) side effects after 2 years, compared with women who did not expect side effects or who only expected mild side effects. The former also reported a lower health-related quality of life than the latter.

Fast facts about breast cancer
  • Over 3 million women living in the United States either have or have had breast cancer
  • Excluding skin cancer, breast cancer is the most common cancer among American women, accounting for 29 percent of newly diagnosed cancers
  • Men get breast cancer, too; in 2015, over 2,000 were diagnosed with it in the U.S.
  • Learn more about breast cancer

"Higher negative expectations, formed by patients before the start of their adjuvant therapy, seem to have a pronounced influence on long-term tolerability," says Prof. Nestoriuc, "especially once they are confirmed by initially high side effects after 3 months."

The findings did not alter after the researchers took into account other factors that might influence experience of side effects, such as the usual demographics, medical history, symptoms present at the outset, and previous menopausal symptoms.

The most frequent reported side effect was joint pain, followed by weight gain and hot flashes. The women also reported other symptoms that could not be directly related to their medication, such as back pain, problems with breathing, and dizziness.

Prof. Nestoriuc says this supports the idea that psychological factors such as negative expectations about treatment can have a strong influence on breast cancer patients' experience of side effects.

The team points out that a possible weakness of their findings is that nearly 40 percent of patients who were eligible to join the study did not do so. Their decision could have been influenced by negative expectations of the therapy.

The researchers are now conducting a randomized controlled trial to see whether intervention that encourages patients to have positive expectations can lessen the side effects they experience.

Such interventions include: having professional counseling just before or during the early part of treatment; receiving information on treatment that highlights its benefits and the possible effects of expectations; and receiving advice about coping with side effects.

"Expectations can be modified so as to decrease the burden of long-term side effects and optimize adherence to preventive anticancer treatments in breast cancer survivors."

Prof. Yvonne Nestoriuc

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