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ESMO Asia 2016: Almost 20% of Swedish Breast Cancer Patients Fail to Complete Prescribed Endocrine Therapy

Key Points

  • Women less than 50 years old were 50% more likely to be nonadherent than 50– to 65-year-olds, with 5% of all nonadherent cases attributable to being in the younger age group.
  • Women who had used hormone replacement therapy were 57% more likely to be nonadherent than those who had not.
  • Unmarried women were 33% more likely to be nonadherent than married women.
  • Unemployed women had 60% higher odds of being nonadherent compared to blue collar workers.
  • White collar women were slightly less likely to adhere to endocrine treatment compared to blue collar patients, but the absolute difference was negligible.

Around 20% of patients with breast cancer in Sweden do not complete endocrine therapy, according to research that will be reported at the ESMO Asia 2016 Congress (Abstract 62O_PR), to be held December 16–19 in Singapore.The study in over 5,500 women found that younger patients and those who had taken hormone replacement therapy were less likely to adhere to their prescribed regimen.

“Adjuvant endocrine treatment, such as tamoxifen, prevents recurrence and improves absolute survival by 5% to 10% in patients with estrogen receptor–positive breast cancer, especially when taken long term (5–10 years),” said lead author Wahyu Wulaningsih, MD, research associate at the MRC Unit for Lifelong Health and Ageing at University College London and cofounder of Philippine and Indonesian Scholars Research and Education.

“A substantial proportion of patients who start this treatment do not complete it,” continued Dr. Wulaningsih. “There is evidence that failure to take the medicine could lead to worse survival. We therefore investigated the reasons for nonadherence so that targeted strategies could be developed.”

Study Details

The study included 5,544 women with estrogen receptor–positive breast cancer who collected at least one prescription of aromatase inhibitors or tamoxifen and had 5 years of follow up data. Women were identified and prescription information was obtained from the regional registers of Uppsala-Örebro, Stockholm-Gotland, and Northern Sweden, which cover around 60% of the Swedish population.

The data were linked to Swedish national registers with information about factors which could influence adherence. Adherence was calculated from the drugs dispensed, and patients were classified as nonadherent if they received less than 80% of the drugs needed over 5 years.

Major Findings

During the 5 years, 20% of the women became nonadherent. In the multivariable analysis, the strongest independent predictors of nonadherence were younger age, previous use of hormone replacement therapy, marital status, and socioeconomic status (measured by type of employment).

Women less than 50 years of age were 50% more likely to be nonadherent than 50– to 65-year-olds, with 5% of all nonadherent cases attributable to being in the younger age group. Women who had used hormone replacement therapy were 57% more likely to be nonadherent than those who had not. Unmarried women were 33% more likely to be nonadherent than married women.

Regarding employment, unemployed women had 60% higher odds of being nonadherent compared to blue collar workers. White collar women were slightly less likely to adhere to endocrine treatment compared to blue collar patients, but the absolute difference was negligible.

Potential Reasons for Nonadherence

Dr. Wulaningsih said, “A proportion of breast cancer patients of reproductive age may be concerned about the potential impact of endocrine treatment on fertility, which could explain why they are more likely to stop taking the drugs. Women who wish to have children after a breast cancer diagnosis need more information about their treatment options.”

“Research is needed to find out if there are any biological differences in women exposed to hormone replacement therapy before undergoing endocrine treatment for breast cancer,” continued Dr. Wulaningsih. “It could be that they are more predisposed to side effects from endocrine treatment. Personalized approaches may improve adherence in these patients by, for example, tailoring the dosage.”

Dr. Wulaningsih speculated that unmarried patients might have less social and emotional support to continue taking endocrine therapy. She said, “Our study identified subgroups of patients who can be targeted with information on the benefits and consequences of endocrine treatment when it is first prescribed and at subsequent visits. Patient support groups could be strengthened, or developed, to help patients overcome the barriers to continuing treatment. Improving adherence should lead to better outcomes for these patients.”

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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