Tamoxifen therapy for patients with breast cancer
Authors: Laetitia Huiart, Cyril Ferdynus, Roch Giorgi
Journal: The Lancet (2013)

Christina Davies and colleagues (March 9, p 805)1Davies C Pan H Godwin J et al.Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial.Lancet. 2013; 381: 805-816Summary Full Text Full Text PDF PubMed Scopus (1553) Google Scholar show that extending tamoxifen from 5 to 10 years reduces recurrence and mortality for women with oestrogen receptor-positive breast cancer. They estimate that 10 years of treatment would nearly halve breast cancer mortality. However, this result raises the question of long-term adherence to treatment. We have recently done a metaregression analysis that synthesises the available data for adherence to hormonal therapy in breast cancer,2Huiart L Ferdynus C Giorgi R A meta-regression analysis of the available data on adherence to adjuvant hormonal therapy in breast cancer: Summarizing the data for clinicians.Breast Cancer Res Treat. 2013; 138: 325-328Crossref PubMed Scopus (70) Google Scholar based on 29 observational studies selected from a comprehensive qualitative review.3Murphy CC Bartholomew LK Carpentier MY Bluethmann SM Vernon SW Adherence to adjuvant hormonal therapy among breast cancer survivors in clinical practice: a systematic review.Breast Cancer Res Treat. 2012; 134: 459-478Crossref PubMed Scopus (488) Google Scholar Taking into account duration and type of treatment as well as study methodology, we noted that only 53% of patients continued their treatment for 5 years. To date, no observational data are available to estimate persistence to treatment after the first 5 years of treatment. In the ATLAS study,1Davies C Pan H Godwin J et al.Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial.Lancet. 2013; 381: 805-816Summary Full Text Full Text PDF PubMed Scopus (1553) Google Scholar with patients still persistent to tamoxifen treatment at 5 years, the extension of treatment resulted in a treatment compliance of less than 70% at 10 years. And this is expected to be lower in real life because adherence is usually higher in clinical trials.4Osterberg L Blaschke T Adherence to medication.N Engl J Med. 2005; 353: 487-497Crossref PubMed Scopus (6484) Google Scholar Moreover, younger women, mainly concerned by long-term tamoxifen treatment, are even less persistent to treatment.5Huiart L Dell'Aniello S Suissa S Use of tamoxifen and aromatase inhibitors in a large population-based cohort of women with breast cancer.Br J Cancer. 2011; 104: 1558-1563Crossref PubMed Scopus (55) Google Scholar Persistence to 10 years of treatment is unknown, but can be expected to be dramatically low in real life. The duration of tamoxifen treatment is key to its efficacy. This efficacy, proven in clinical trials, is likely to be reduced in real life if interventions to improve adherence to treatment are not systematically promoted. We declare that we have no conflicts of interest. We thank Arianne Dorval for her assitance. Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trialFor women with ER-positive disease, continuing tamoxifen to 10 years rather than stopping at 5 years produces a further reduction in recurrence and mortality, particularly after year 10. These results, taken together with results from previous trials of 5 years of tamoxifen treatment versus none, suggest that 10 years of tamoxifen treatment can approximately halve breast cancer mortality during the second decade after diagnosis. Full-Text PDF Open AccessTamoxifen therapy for patients with breast cancer – Authors' replyKey findings from trials of 5 years or 10 years of tamoxifen are summarised in the table. They are remarkable. Full-Text PDF