The Study: We recently learned the rates of distant recurrence at 20 years for women with early stage, hormone receptor-positive breast cancer are shockingly high. Good news is several trials have demonstrated improved cancer-specific and even overall survival with extended endocrine therapy beyond 5 years. Bad news is compliance with even 5 years is less than ideal, so a decade of treatment is a serious commitment. Now we have the Clinical Treatment Score post-5 years (CTS5), developed as a simple tool to estimate distant failure rate after stopping endocrine therapy at 5 years. Based on cohorts from the ATAC and BIG 1-98 trials, the following equation was derived to calculate the score: CTS5 = 0.438 x nodes + 0.988 x (0.093 x size - 0.001 x size^2 + 0.375 x grade + 0.017 x age). Order of operations sidebar for the English majors out there: don’t forget to multiply before you add/subtract. A score of <3 correlates with a <5% risk of distant recurrence, between 3 to 4 the risk rises from 5 to 10%, and there is an exponential rise in risk beyond a score of 4. Not unexpected, the model is dominated by nodal status, age, and grade.
Bottom Line: Use the CTS5 to calculate the risk of distant recurrence after stopping endocrine therapy at 5 years to help you decide who may actually benefit from grinning and bearing more extended treatment. | Dowsett, J Clin Oncol 2018