Endocrine therapy in the years following a diagnosis of breast cancer: A proof of concept study using the primary care prescription database linked to cancer registration data.

Introduction: National cancer registration data were linked to the Primary Care Prescription Database (PCPD) in England. The level of endocrine therapy (ET) prescribed in women after a diagnosis of breast cancer was studied.
Materials and Methods: Cancer registrations for women diagnosed with breast cancer during 1995-2015, who survived to 31st March 2015, were linked to ET prescriptions issued during April-July 2015.
Results: Among 369 277 survivors of breast cancer diagnosed during 1995-2015, 37% were prescribed ET during April-July 2015. Among women whose breast cancer diagnosis was after 31st July 2010, 81% of those recorded with oestrogen receptor positive (ER+ve) disease were prescribed ET compared with only 6% of those with ER-ve disease. Younger women usually received tamoxifen and older women usually received aromatase inhibitors.
Discussion: The pattern of ET use observed in these data corresponds to that expected. This provides confidence in the potential of the PCPD for epidemiological research.
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