A world-wide meta- analysis involving the results of 88 clinical trials determined breast cancer recurrence outcomes 5-20 years after endocrine therapy.
Endocrine therapy has proven quite beneficial for breast cancer therapy, even significantly reducing breast cancer recurrence in estrogen-receptor-positive patients when administered adjuvantly for five years. Furthermore, extending the time for which adjuvant endocrine therapy is administered past five years may also continue to reduce the risk of recurrence.
For some women, however, endocrine therapy has proven to have harsh and consequential side effects. This can involve extremely life-threatening side effects such as pulmonary embolus and endometrial cancer. It has been demonstrated that the risk of extreme side effects increases with longer endocrine therapy regimens. It must be said that many things need to be taken into consideration to determine whether or not to extend endocrine therapy past five years. To truly get to the bottom of this, researchers first had to figure out if the risk of breast cancer recurrence remains after five years of endocrine therapy.
A world-wide meta-analysis led by Hongchao Pan and colleagues alongside the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) wanted to understand the long-term incidence of patient outcomes in women with ER-positive, early-stage breast cancer who had been given adjuvant endocrine therapy. Their results were recently reported in the New England Journal of Medicine.
For this analysis, over 62,000 women who had ER-positive breast cancer and were cancer-free five years post-endocrine therapy were included. The analysis grouped findings according to their trial and treatment. This was done so that that the researchers could get a better understanding between the correlation of tumor diameter and nodal status, grade, and other factors with patients’ outcomes from 5 to 20 years following adjuvant therapy.
The researchers found many interesting results. During the 5 to 20 year study, the risk of recurrence among the patients was significantly correlated to the initial nodal status of the tumor; recurrence risk increased steadily as nodal status increased. This was also reflected when the risk of recurrence was demonstrated for contralateral breast cancer. They also showed that the risk of recurrence remained on a steady increase up to 20 years from initial diagnosis. The researchers also demonstrated that although recurrence in the first five years following endocrine therapy was slim to none, the risk of cancer recurring somewhere else in the body from 5 to 20 years was steady.
These results demonstrate that nodal status in ER-positive breast cancer is associated with recurrence in patients. The researchers state that these patients should carefully consider the risks and benefits of taking endocrine therapies beyond five years. Although this study has many pros, the researchers did note that the women who were used as part of this meta-analysis were diagnosed and given therapy, years, maybe even decades ago. This was a time when treatments were not as advanced as they currently are. This leads scientists to believe that breast cancer recurrence rates for women who have been diagnosed with ER-positive breast cancer more recently could be lower than that reported in this study.
Written by Ingrid Qemo, BSc
Reference: Pan, H., Gray, R., Braybrooke, J., et al. 2017. 20-year risks of breast-cancer recurrence after stopping endocrine therapy at 5 years. N Engl J Med. 377:1836-1846.
