Clinical Treatment Score post-5 years as a predictor of late distant recurrence in hormone receptor-positive breast cancer: systematic review and meta-analysis

Background: The Clinical Treatment Score post-5 years (CTS5) integrates four clinicopathological variables to estimate the residual disease recurrence risk in hormone receptor-positive breast cancer patients who have been treated with five years of adjuvant endocrine therapy. This study aimed to determine the accuracy of the CTS5. Methods: A systematic review was performed in accordance with the PRISMA statement. Studies relevant for inclusion in the current review were identified from The Cochrane Library, EBSCO, Ovid, PubMed, and Embase. Results: Six papers reported on 30 354 postmenopausal patients (age range 42 to 91 years). The pooled hazard ratio (HR) of distant recurrence relative to the low-risk CTS5 category was 5.41 (95% c.i. 4.50 to 6.51; P < 0.05) for the high-risk CTS5 category and 2.32 (95% c.i. 1.90-2.84; P < 0.05) for the intermediate CTS5 category. Three papers reported on 10 425 premenopausal patients (age range 18 to 54 years). The pooled HR of distant recurrence relative to the low-risk CTS5 category was 5.42 (95% c.i. 2.26 to 13.01; P < 0.05) for the high-risk CTS5 category and 2.82 (95% c.i. 1.35 to 5.88; P < 0.05) for the intermediate CTS5 category. Relative to high-risk postmenopausal patients, the mean observed 10-year distant recurrence risk for the high CTS5 category was 13.83 per cent, which differs significantly from the CTS5 estimation of 10-year distant recurrence risk (20.3 per cent, 95% c.i. 17.2 to 24; P = 0.000). Conclusion: The CTS5 can predict late distant recurrence risk in pre-and postmenopausal hormone receptor-positive breast cancer patients. CTS5 overestimates the risk for high-risk patients and thus, its use in these patients warrants caution.