Abstract PO2-17-07: Risk analysis of the differences in eligibility criteria between monarchE and POTENT clinical trials
Authors: Yu Muhan , Takada Mamoru , Yamada Hideyuki , Fujimoto Hiroshi , Sakakibara Junta , Yamamoto Hiroto , Nagashima Takeshi , Otsuka Masayuki 
Published: May 2024

Abstract
Background
Luminal subtype recurrence risk classifications for breast cancer have been updated and put into practice with the development of treatment. Despite this, it is noteworthy that from 2008 to 2016, early breast cancer (EBC) of luminal subtype has been reported to have little improvement in survival probability. For early-stage luminal breast cancer, several clinical trials, such as monarchE, NATALEE (which is not available in Japan) or POTENT, were being conducted. In order to avoid overtreating individuals who might not benefit from adjuvant therapy, those at high risk of recurrence ought to be accurately picked up. In monarchE and POTENT trials, abemaciclib and S-1 have shown to be effective in adjuvant therapies for luminal breast cancer although it is unrevealed if the eligible patients for each criterion are at higher risk of recurrence than ineligible patients. Besides, some of the eligibility for POTENT overlaps with those for monarchE, the patients who met POTENT but did not meet monarchE criteria at how much risk of recurrence still remains unknown. Here, we investigated recurrence risk according to the criteria of each trial in Japanese patients in real world.
Methods
We reviewed the records of 1209 patients who received surgery for stage I–III breast cancer from January 2016 to May 2022 and selected 637 analytic cohort patients and retrospectively analyzed the recurrence-free survival (RFS) of the patients using the Kaplan–Meier method. High-recurrence-risk was defined according to monarchE trial and POTENT trial. Patients’ RFS was the primary endpoint.
Results
The 5-year RFS for all luminal breast cancer patients was 94.87% at Chiba University Hospital. Among monarchE eligible patients, the 5-year RFS was 82.49% and cohort 1 and cohort 2 eligible patients was 78.62% and 92.18% respectively, which were statistically lower than monarchE non-eligible patients (98.58%) (p &lt; 0.0001, p = 0.0216, respectively). Even though the 5-year RFS rate for POTENT eligible patients (91.16%) was lower than POTENT non-eligible patients (99.13%) (p &lt; 0.0001), while excluding those who met the monarchE criteria, the prognosis of POTENT eligible patients (5-year RFS rate 97.76%) had no significant differences from the patients with POTENT non-eligible breast cancer (p =0.0660).
Our results suggested that the eligible patients of both monarchE and POTENT were associated with poor prognoses so the criteria set are considered to be appropriate. However, although POTENT criteria suggested a reasonable capacity for recurrence prediction, there was no dramatic difference in recurrence between POTENT non-eligible patients and the patients who are POTENT eligible but are not monarchE eligible. This might offer justification for reconsidering the use of S-1 in monarchE non-eligible patients. With the use of clinicopathological factors, it may assist in identifying individuals with high recurrence risk who would benefit from lengthier adjuvant chemotherapy regimens.
Conclusion
MonarchE criteria accurately identifies patients at high risk of relapse but the relapse in the patients who only qualified for POTENT is statistically almost the same as that in POTENT non-eligible patients.
Citation Format: Muhan Yu, Mamoru Takada, Hideyuki Yamada, Hiroshi Fujimoto, Junta Sakakibara, Hiroto Yamamoto, Takeshi Nagashima, Masayuki Otsuka. Risk analysis of the differences in eligibility criteria between monarchE and POTENT clinical trials [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-17-07.