Endocrine therapy is administered to hormone-positive breast cancer patients to prevent distant metastasis. It is important to evaluate the risk of recurrence and to determine which patients are viable candidates for such treatment because hormone therapy has side effects that can include postmenopausal symptoms. The Clinical Treatment Score post–five years (CTS5), a simple tool for identifying candidates for endocrine therapy, was recently introduced; however, CTS5 only has been applied in validation studies with postmenopausal women. We aimed to validate CTS5 among premenopausal breast cancer patients.
We identified patients treated between 1994 and 2014 at Samsung Medical Center in Seoul, Korea, and followed their treatment outcomes for more than 60 months after surgery using clinicopathologic parameters. According to menopausal status, we divided the study population into two groups: pre- and postmenopausal women. After calculating CTS5 values based on some parameters, we stratified the rate of late distant recurrence (DR) and analyzed the correlation between CTS5 value and late DR by risk.
Among 16,904 patients treated surgically for breast cancer, 2,605 with hormone receptor–positive breast cancer who received endocrine therapy were included. Of these, 1,749 (67.14%) patients were premenopausal women, and the median age was 44.00 years. When categorizing study participants according to CTS5-related risk for late DR, 86.79% were categorized as low risk, 5.95% were categorized as intermediate risk, and 7.26% were categorized as high risk. The annual rate of DR was 1.41% for those in the present study and was similar between pre- and postmenopausal participants (1.40 vs. 1.42). Distant metastasis-free survival was not different between the two groups (hazard ratio: 0.817, 95% confidence interval [CI]: 0.547–1.221). The area under the receiver operating characteristic curve at 10 years for premenopausal and postmenopausal patients was 61.75 (95% CI: 52.97–70.53) and 72.71 (95% CIs: 63.30–82.12), respectively.
Although CTS5 was able to predict late DR, it should be applied with caution in premenopausal women. A CTS5 calculator for premenopausal women might be needed to not underestimate the risk of recurrence in Korea.