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Asia Pac J Clin Oncol. 2017 Apr;13(2):e161-e170. doi: 10.1111/ajco.12600. Epub 2016 Oct 14.

Switching between endocrine therapies for primary breast cancer: Frequency and timing in Australian clinical practice.

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University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
Quality Use of Medicines and Pharmacy Research Centre, School of Pharmacy and Medical Sciences, University of South Australia, GPO Box 2471, Adelaide, SA, 5001, Australia.
Patricia Richie Centre for Cancer Care and Research, The Mater Hospital and University of Sydney, Rocklands Road, Sydney, NSW, 2060, Australia.
Institute of Health Research, University of Notre Dame, PO Box 1225, Fremantle, WA, 6959, Australia.



To determine the frequency, timing and patterns of endocrine therapy switching in Australian practice for postmenopausal women with primary breast cancer.


We identified postmenopausal women in a population-based cohort commencing endocrine therapy for invasive primary breast cancer between December 2005 and December 2008 (n = 645). Individual-level administrative health records and self-report data were used to determine women's demographic and clinical characteristics, including preexisting and newly-treated comorbidities, and switches in endocrine therapy. Time to therapy switching was calculated. Chi-square tests compared the characteristics of women who did and did not switch, and those switching within 2 years or after 2 years of commencing therapy.


Twenty-eight percent of women switched from their initial endocrine therapy, most commonly from tamoxifen to anastrozole, or the converse. A small number of anastrozole-to-exemestane and letrozole-to-exemestane switches were observed (n = 19). Most women (>80%) who switched therapies did not have newly-treated comorbidities. Few women (<5%) switched before completing 2 years of therapy, but these women were significantly more likely to have preexisting antidepressant use than women switching later (43% vs 23%, P = 0.048) and remained on the subsequent therapy for less time (6 months vs 2.7 years, P < 0.001).


Approximately one-quarter of postmenopausal women with primary breast cancer switched endocrine therapies. The findings suggest that the majority of switching in Australian practice was planned; occurring after 2-3 years of, not precipitated by comorbidity, and in a sequence supported by trial evidence. Early switching, however, was associated with preexisting depression and appeared to be a marker of poor persistence.


45 and Up Study; breast cancer; clinical guidelines; clinical practice; duration of therapy; endocrine therapy; switch

[Indexed for MEDLINE]

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