Abstract P5-06-22: Validation of CTS5 in premenopausal breast cancer patients and the role of Ki67 among risk-stratification groups
Authors: Lee Janghee , Ahn Sung Gwe , Cha Chihwan , Bae Soong June , Kim Dooreh , Park Soeun , Jeong Joon 
Published: March 2020

Background: The Clinical Treatment Score at 5 years (CTS5) could be applied to identify the patients who could recommend an extension of endocrine therapy more than 5 years. In the low-risk group by CTS5, there is a limited benefit in extending endocrine therapy when patients are free from distant recurrence (DR) for 5 years. However, it raises concerns that late recurrence could occur even in the low-risk group of CTS5, and thus an issue to find factors affecting late recurrence arises in those. Furthermore, it remains unclear whether CTS5 could be adopted for premenopausal women in same context. In this study, we investigated data from patients with ER-positive breast cancer who had been free of 5-years distant recurrence. We aimed whether CTS5 is helpful to predict late DR in premenopausal and which affects late DR in the low-CTS5 group.

Methods: From January 2006 to December 2013, 666 patients who had ER-positive breast cancer and had been free from 5 years DR after operation were identified. Of these, we calculated CTS5 scores using clinical variables. About 60% of the patients were premenopausal (393 of 666; 59%). To identify factors associated with late DR in the low-CTS5 group, binary logistic regression analysis was used.

Results: Among all patients, late DR occurred in 25 patients. Of all patients, 402 women (60.4%) were with CTS5 low-risk group, and 10 of them (2.5%) had late DR. There were also 73 women (11%) CTS5 high-risk group, of whom 9 (12.3%) had late DR. In Kaplan-Meier analysis, the incidence of late DR was significantly increased in the high-CTS5 group (P &lt; 0.001). Similarly, premenopausal women had higher rates of late DR in the high-CTS5 group (P = 0.049). In the low-CTS5 group, patients with late DR had higher Ki-67 labelling index (L.I.) compared with those without late DR (patients with Ki-67 level above 20; late DR 2/10 (22.2%) vs. without late DR 20/390 (5.1%), p = 0.027). In the multivariable analysis, Ki-67 level was found as a significant predictor for late DR in low-CTS5 group [odds ratio (OR), 11.870; CI 95%, 1.821-77.383; P = 0.010]. In other intermediate- or high-CTS5 groups, Ki67 L.I. was not associated with late DR.

Conclusion: We found that CTS5 was useful to identify premenopausal women who are at risk of late DR, although CTS5 algorithm was developed by cohorts consisted of postmenopausal women. Also, the Ki67 level is helpful estimate a substantial risk of late DR in the low-CTS5 patients who are expected to have low chance of DR after 5 years endocrine therapy.

Univariable and multivariable analysis in CTS5-low risk groupUnivariableMultivariableNo late DR(n=392)Late DR(n=10)p valueOR(95% CI)p valueAge49.7(±9.56)48.0(±9.32)0.5841.002(0.932-1.078)0.956pT stagepT1352(89.8%)7(70.0%)0.0451pT240(10.2%)3(30.0%)4.600(1.030-20.551)0.046pN stagepN0355(90.6%)10(100%)0.3081pN137(9.4%)0(0%)00.998Histologic gradeLow195(49.7%)6(60.0%)0.7141Intermediate182(46.4%)4(40.0%)0.381(0.085-1.719)0.210High15(3.8%)0(0%)00.998Ki67≤ 20369(94.1%)7(70.0%)0.0271&gt; 2020(5.1%)2(20.0%)11.870(1.821-77.383)0.010Unknown3(0.8%)1(10.0%)

Citation Format: Janghee Lee, Sung Gwe Ahn, Chihwan Cha, Soong June Bae, Dooreh Kim, Soeun Park, Joon Jeong. Validation of CTS5 in premenopausal breast cancer patients and the role of Ki67 among risk-stratification groups [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-22.