The clinical value of clinical treatment score post-5 years in patients with premenopausal breast cancer: a retrospective analysis of ASTRRA trial.

BACKGROUND: The Clinical Treatment Score post-5 years (CTS5), a prognostic tool for late distant recurrence, was validated in postmenopausal patients, but its value in premenopausal women remains unclear. Using 8-year ASTRRA data, we evaluated the prognostic performance of CTS5 in premenopausal breast cancer patients. METHODS: Patients without any event within the first 5 years were included in this analysis and were categorized into three risk groups based on CTS5 cutoff values. Late distant metastasis-free survival (DMFS) and overall survival were analyzed. Subgroup analyses were conducted to compare outcomes between the tamoxifen (TAM)-only and TAM + ovarian function suppression (OFS) groups. RESULTS: Of the 1028 included premenopausal patients, late distant metastasis rates were 3.43% (low-risk, n = 466), 2.56% (intermediate-risk, n = 312), and 9.63% (high-risk, n = 270). The high-risk group showed a significantly higher risk of late DMFS compared to the low-risk group (HR = 3.32; 95% CI: 1.73-6.37; p < 0.001). The intermediate-risk group showed no significant difference (HR = 1.06; p = 0.876). When combining the low/intermediate-risk groups, the high-risk group maintained a significantly elevated risk (HR = 3.16; p = 0.015). OS results were consistent. Subgroup analysis confirmed that CTS5's prognostic ability was maintained in both the TAM-only (HR = 3.23; 0 = 0.004) and TAM + OFS groups (HR = 3.49; p = 0.029), consistently identifying high-risk patients. CONCLUSION: In this randomized trial, unmodified CTS5 identifies high-risk patients but exhibits threshold inversions, making it unreliable for premenopausal extended therapy.