Is the CTS5 a helpful decision-making tool in the extended adjuvant therapy setting?

Area of Science:

• Oncology
• Clinical Medicine
• Biostatistics

Background:

• The Clinical Treatment Score post-5 years (CTS5) is a prognostic tool for hormone receptor-positive breast cancer.
• Endocrine therapy (ET) is standard for 5 years, but extended ET may benefit select patients.
• ABCSG-06 and -06a trials provide data for evaluating CTS5's utility.

Purpose of the Study:

• To assess the prognostic value and calibration accuracy of the CTS5 score.
• To determine if CTS5 can identify patients who benefit from extended endocrine therapy (ET).
• To evaluate the risk of late distant recurrence (LDR) beyond 5 years of ET.

Main Methods:

• Prospective analysis of 2114 patients from ABCSG-06 and -06a trials.
• Cox regression models were used to analyze time to LDR.
• Evaluation of CTS5's prognostic power, calibration, and predictive value for extended ET benefit.

Main Results:

• Higher LDR rates were observed in high- and intermediate-risk CTS5 groups (HR 4.02 and 1.93, respectively).
• An increasing CTS5 score correlated with increased LDR risk (HR 2.23).
• Miscalibration of CTS5 was noted in high-risk patients; a trend suggested benefit from extended ET (absolute LDR reduction of -6.1%).

Conclusions:

• CTS5 is a reliable prognostic tool, well-calibrated for low and intermediate risk groups.
• Substantial differences in observed vs. expected LDR rates in high-risk patients were found.
• The study did not confirm a significantly predictive value of CTS5 for extended ET benefit, despite a numerical trend.