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J Breast Cancer. 2019 Mar 11;22(1):86-95. doi: 10.4048/jbc.2019.22.e14. eCollection 2019 Mar.

Prescription Refill Gap of Endocrine Treatment from Electronic Medical Records as a Prognostic Factor in Breast Cancer Patients.

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Department of Biomedical Informatics, Asan Medical Center, Seoul, Korea.
Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Department of Biomedical Systems Informatics, Yonsei University College of Medicine, Seoul, Korea.
Clinical Research Center, Asan Medical Center, Seoul, Korea.



Discontinuation of hormone therapy is known to lead to a poorer prognosis in breast cancer patients. We aimed to investigate the prescription gap as a prompt index of medication adherence by using prescription data extracted from patient electronic medical records.


A total of 5,928 patients diagnosed with invasive, non-metastatic breast cancer, who underwent surgery from January 1, 1997 to December 31, 2009, were enrolled retrospectively. The prescription data for 4.5 years of hormonal treatment and breast cancer-related events after treatment completion were analyzed. We examined the characteristics and prognoses of breast cancer in patients with and without a 4-week gap.


Patients with a gap showed a significantly higher risk of breast cancer recurrence, distant metastasis, breast cancer-specific death, and overall death after adjustment (hazard ratio [HR], 1.389; 95% confidence interval [CI], 1.089-1.772; HR, 1.568; 95% CI, 1.158-2.123; HR, 2.108; 95% CI, 1.298-3.423; and HR, 2.102; 95% CI, 1.456-3.034, respectively). When patients were categorized based on gap summation, the lower third (160 days) and fourth (391 days) quartiles showed a significantly higher risk of distant metastasis (HR, 1.758; 95% CI, 1.186-2.606 and HR, 1.844; 95% CI, 1.262-2.693, respectively).


A gap of > 4 weeks in hormonal treatment has negative effects on breast cancer prognosis, and can hence be used as a sentinel index of higher risk due to treatment non-adherence. Further evaluation is needed to determine whether the gap can be used as a universal index for monitoring the adherence to hormonal treatment.


Breast neoplasms; Estrogen antagonists; Medication adherence; Neoplasm metastasis

Conflict of interest statement

Conflict of Interest: The authors declare that they have no competing interests, and there are no financial conflicts of interest to disclose.

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