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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.