Effect of Patient-Reported Symptoms on Adherence to Preventive Treatment for Breast Cancer

Key Points

  • Although adherence was poorer in the tamoxifen group, the effects of symptoms were similar in both groups.
  • Long-term adherence was reduced by the experience of symptoms in the first 6 months of treatment.

In an analysis of the UK cohort of the International Breast Cancer Intervention Study (IBIS-I) reported in the Journal of Clinical Oncology, Smith et al found similar effects of predefined symptoms on nonadherence in both tamoxifen and placebo recipients. IBIS-I randomized women at high risk of breast cancer to receive tamoxifen or placebo for 5 years.

Study Details

A total of 3,823 women were included in the current analysis. Adherence was calculated using data from clinical visits every 6 months. The predefined symptoms consisted of nausea, vomiting, headaches, hot flashes, irregular bleeding, vaginal dryness, and vaginal discharge.

Factors in Nonadherence

Overall, 69.7% of women were adherent for ≥ 4.5 years, including 65.2% of those in the tamoxifen group and 74.0% of those in the placebo group (P < .001). Differences between groups in adherence at this level were observed from 12 months onward (all P < .01), with the greatest difference observed at 54 months. Dropout rates were highest during the first 12 to 18 months.

Individual symptoms significantly associated with a reduced likelihood of adherence consisted of nausea/vomiting in both the tamoxifen (odds ratio [OR] = 0.57, P = .007) and placebo groups (OR = 0.58, P = .023), headache in the placebo group (OR = 0.62, P = .016), and gynecologic symptoms in the tamoxifen group (OR = 0.77, P = .024). There was no significant difference between the groups for effect sizes for each symptom on adherence (all P > .5). In both groups, increasing severity was associated with lower adherence for all symptoms (P < .01) except headache (P = .054). Overall, more than half (53%) of nonadherence was explained by the treatment group (P < .001), with an additional 22% explained by reporting any of the predefined symptoms at 6 months (P = .002).

The investigators concluded: “In the IBIS-I trial, experiencing predefined symptoms in the first 6 months reduced long-term adherence. Effects were similar between treatment arms, suggesting that women were attributing age-related symptoms to preventive therapy. Interventions [are] required to support symptom management.”

Samuel George Smith, PhD, of the University of Leeds, is the corresponding author of the Journal of Clinical Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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