Improvements in long-term outcome for women with estrogen receptor positive (ER+) early stage breast cancer

15 December 2019

Pan H et al.

Background

For women with ER+ early stage breast cancer who are disease-free after 5 years of scheduled endocrine therapy, recurrences occur at a steady rate to at least year 20 from diagnosis, and are strongly correlated with tumor and nodal status (TN). For women diagnosed in 1976-2011, 20-year distant recurrence (DR) risk was 13%, 20%, and 34% for T1N0, T1N1-3, and T1N4-9 disease, respectively (Pan et al NEJM 2017). Using updated data, we investigated whether DR risk is lower for women diagnosed more recently.

Methods

Kaplan-Meier and Cox regression analyses, stratified by trial, TN status and treatment, included 82,598 women with ER+ breast cancer from 108 trials who were alive and disease free after 5 years of scheduled endocrine therapy, 19,675 more than in the previously published dataset, of whom 11,391 were diagnosed since 2005.

Results

Estimates of DR during the period from 5 to 20 years were 1% to 2% lower in the updated dataset than reported in 2017. Compared to earlier years (before 1995), the hazard ratio (HR) for DR in years 5-9 was 0.83 (95%CI 0.77 – 0.90) in women diagnosed in 1995-99, decreasing to 0.64 (0.59 – 0.70) in 2000-04, and to 0.58 (0.52 – 0.65) in 2005-12. Those diagnosed after 2000 (median follow-up after year 5 = 2.7, IQR 1.1-4.3 years) had a 30% lower risk of DR (HR = 0.70 (95% CI 0.66 – 0.75) compared with women diagnosed before 2000 (median follow-up after year 5 = 6.1, IQR 4.4-9.9 years). The recurrence risk in years 5-10 after diagnosis in women diagnosed after 2000 was 3% for T1N0 and 5% for T2N0, with few events recorded after year 10. If these recurrence rates continue at the same rate, 20-year risk of DR for women diagnosed after 2000 is projected to be 8% and 14% for T1N0 and T2N0 stages, respectively, compared with 13% and 19% for those diagnosed before 2000. More detailed analyses and investigation of factors influencing the improvements in outcome will be presented.

Conclusion

The risk of DR at 20 years after diagnosis for women with node-negative ER+ early stage breast cancer, who discontinue endocrine therapy at 5 years is likely to be about a third lower now than in our previous report. However, long-term follow-up of patients diagnosed more recently is required to accurately characterize long-term recurrence risks.