Long Term Risk of Breast Cancer Recurrence after Stopping Endocrine Therapy at 5 Years

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that 252,710 new cases of invasive breast cancer and 63,410 new cases of non-invasive breast cancer will be diagnosed in women in 2017 and 40,610 women are expected to die from the disease.

It has been well established that treatment with 5 years of endocrine therapy in early stage, Estrogen Receptor (ER) positive breast cancer, significantly reduces the risks of locoregional and distant recurrence, contralateral breast cancer, death from breast cancer, and therefore death from any cause. Extended adjuvant endocrine therapy with either Tamoxifen or an Aromatase Inhibitor (AI) beyond 5 years can further reduce breast cancer recurrence. This however can result in treatment related side effects. Therefore, when considering extended adjuvant endocrine therapy beyond 5 years, the potential benefits should be weighed against the associated risk with such therapy. The absolute benefit of continuing endocrine therapy after 5 years depends on the absolute risk of later recurrence, if patient’s receives no further therapy.

The authors in this publication reported the influence of original tumor characteristics, on the incidence of breast cancer outcomes, over a 20 year period. This meta-analysis included data from 88 trials in the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) database of randomized trials, involving 62,923 women with ER-positive breast cancer, who were disease-free after 5 years of adjuvant endocrine therapy. Data was analyzed from women who had T1 disease (Tumor diameter 2 cm or less) or T2 disease (Tumor diameter more than 2 cm up to 5 cm), no positive nodes (N0), 1-3 positive nodes (N1-3), 4-9 positive nodes (N4-9), and no distant metastases. The authors then assessed the associations of Tumor diameter and Nodal status (TN), tumor grade, and other factors with patients’ outcomes, during the period from 5 to 20 years.

It was noted that distant breast cancer recurrences occurred at a steady rate for at least another 15 years after completing 5 years of adjuvant hormonal treatment. The risk of distant recurrence strongly correlated with the original Tumor diameter and Nodal status (TN status).

Among women with T1 disease, the risk of distant recurrence was 13% in those with T1N0 disease, 20% in those with T1N1-3 disease and 34% in those with T1N4-9 disease. Even in those women with low grade T1N0 breast cancer, the absolute risk of distant recurrence from 5-20 years was 10%.

Among those with T2 disease, the risk of distant recurrence was 19% with T2N0 disease, 26% with T2N1-3 disease, and 41% with T2N4-9 disease. TN status was also a strong determinant of locoregional recurrence, but not predictive for contralateral breast cancer.

There was a strong association of tumor grade and Ki-67 status with the risk of distant recurrence during the first 5 years but had limited additional prognostic relevance during years 5-20. Similarly, patients with negative Progesterone Receptor (PR) had a worse prognosis during the first 5 years but not thereafter.

The authors concluded that even after 5 years of adjuvant endocrine therapy, women with ER-positive, early stage breast cancer, continue to be at risk for recurrence and death from breast cancer, for at least 20 years after the original diagnosis. This risk varies from 10-41% and is strongly dependent on TN status at the time of initial diagnosis. Even those with low-grade T1N0 disease were at an appreciable risk of distant recurrence. Extended adjuvant endocrine therapy beyond 5 years may reduce this risk, and this study highlights the need for new approaches to reduce late recurrence. 20-Year Risks of Breast-Cancer Recurrence after Stopping Endocrine Therapy at 5 Years. Pan H, Gray R, Braybrooke J, et al. for the EBCTCG. N Engl J Med 2017; 377:1836-1846