Women commencing anastrozole, letrozole or tamoxifen for early breast cancer: the impact of comorbidity and demographics on initial choice

• Published in: PloS one Vol. 9; no. 1; p. e84835
• Main Authors: Kemp, Anna, Preen, David B, Saunders, Christobel, Boyle, Frances, Bulsara, Max, Holman, C D'Arcy J, Malacova, Eva, Roughead, Elizabeth E
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 02-01-2014; Public Library of Science (PLoS)
• Subjects: Adult; Aged; Aged, 80 and over; Analysis; Anastrozole; Antineoplastic agents; Antineoplastic Agents, Hormonal - therapeutic use; Aromatase; Aromatase inhibitors; Aromatase Inhibitors - therapeutic use; Arthritis; Australia; Biocompatibility; Biomedical materials; Breast cancer; Breast Neoplasms - drug therapy; Breast Neoplasms - pathology; Cancer; Cancer research; Cancer therapies; Care and treatment; Cohort Studies; Comorbidity; Data collection; Demographics; Demography; Dispensing; Endocrine therapy; Ethics; Female; Government agencies; Guidelines; Health aspects; Health risk assessment; Health services; Humans; Identification methods; Invasiveness; Letrozole; Medical diagnosis; Medical research; Medicine; Menopause; Middle Aged; Neoplasm Staging; Nitriles - therapeutic use; Osteoporosis; Patients; Postmenopausal women; Postmenopause; Practice guidelines (Medicine); Practice Guidelines as Topic; Premenopause; Regression analysis; Regression models; Research methodology; Researchers; Selective Estrogen Receptor Modulators - therapeutic use; Studies; Tamoxifen; Tamoxifen - therapeutic use; Therapy; Triazoles - therapeutic use; Tumor Burden; Tumors; Womens health; Australia; Western Australia Australia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0084835

Australian clinical guidelines recommend endocrine therapy for all women with hormone-dependent early breast cancer. Guidelines specify tamoxifen as first-line therapy for pre-menopausal women, and tamoxifen or an aromatase inhibitor (AI) for post-menopausal women depending on the risk of recurrence based on tumour characteristics including size. Therapies have different side effect profiles; therefore comorbidity may also influence choice. We examined comorbidity, and the clinical and demographic characteristics of women commencing different therapies.
We identified the first dispensing of tamoxifen, anastrozole or letrozole for women diagnosed with invasive breast cancer in the 45 and Up Study from 2004-2009 (N = 1266). Unit-level pharmacy and medical service claims, hospital, Cancer Registry, and self-reported data were linked to determine menopause status at diagnosis, tumour size, age, comorbidities, and change in subsidy restrictions. Chi-square tests and generalised regression models were used to compare the characteristics of women commencing different therapies.
Most pre-menopausal women commenced therapy with tamoxifen (91%). Anastrozole was the predominant therapy for post-menopausal women (57%), followed by tamoxifen (28%). Women with osteoporosis were less likely to commence anastrozole compared with tamoxifen (anastrozole RR = 0.7, 95% CI = 0.5-0.9). Women with arthritis were 1.6-times more likely to commence letrozole than anastrozole (95% CI = 1.1-2.1). Tamoxifen was more often initiated in women with tumours >1 cm, who were also ≥75 years. Subsidy restriction changes were associated with substantial increases in the proportion of women commencing AIs (anastrozole RR = 4.3, letrozole RR = 8.3).
The findings indicate interplay of comorbidity and therapy choice for women with invasive breast cancer. Most post-menopausal women commenced therapy with anastrozole; however, letrozole and tamoxifen were more often initiated for women with comorbid arthritis and osteoporosis, respectively. Tamoxifen was also more common for women with tumours >1 cm and aged ≥75 years. Subsidy restrictions appear to have strongly influenced therapy choice.