Abstract 153P
Background
MonarchE demonstrated that adjuvant abemaciclib, oral CDK4 & 6 inhibitor + endocrine therapy (ET) significantly improved invasive disease-free survival in HR+, HER2- high-risk early breast cancer (EBC) compared to ET alone. As prescribing practices for ET vary in younger patients (pts), we present here disease characteristics and ET choice in premenopausal pts (preM) enrolled in monarchE.
Methods
Patients with, invasive, resected, HR+, HER2- node positive, high risk, EBC were randomly assigned 1:1 to adjuvant ET +/- abemaciclib in monarchE. Disease characteristics, prior chemotherapy, and ET patterns were examined by menopausal status at initial diagnosis: preM and postmenopausal pts (postM). ET choices for preM are further described by age.
Results
Of the 5637 pts, 43.5% and 56.5% were preM and postM, respectively, with an even distribution between both arms. Median age for preM and postM was 44 and 59 years (y), respectively; 31.5% of preM were ≤40y. PreM had larger tumor size and higher rates of neoadjuvant chemotherapy administration compared to postM (Table). Aromatase inhibitor (AI) use was higher in postM, while tamoxifen use was higher in preM. Among preM, AI use was highest in preM ≤40y in both arms (49.9% abemaciclib + ET, 49.4% ET) and tamoxifen use was highest in preM >40y to ≤50y in both abemaciclib + ET and ET arms, 60.1% and 65.0%, respectively. Table: 153P
Summary of baseline characteristics and first endocrine therapy for premenopausal and postmenopausal patients
| PreM | PostM | |||
| Abemaciclib + ET N=1227, % | ET Alone N=1224, % | Abemaciclib + ET N=1576, % | ET AloneN=1605, % | |
| Age (years) | ||||
| ≤40 | 31 | 32 | 1 | 2 |
| >40 to ≤50 | 58 | 57 | 15 | 14 |
| >50 | 12 | 10 | 84 | 84 |
| Tumor size at diagnosis | ||||
| <5cm | 75 | 76 | 81 | 82 |
| ≥5cm | 21 | 21 | 15 | 14 |
| Prior chemotherapy | ||||
| Neoadjuvant | 42 | 42 | 32 | 32 |
| Adjuvant | 56 | 55 | 60 | 60 |
| None | 2 | 3 | 8 | 8 |
| Region | ||||
| Asia | 28 | 28 | 15 | 15 |
| NA/EU | 49 | 49 | 55 | 55 |
| Other | 24 | 23 | 30 | 30 |
| 1st ET | ||||
| AI | 43 | 40 | 90 | 89 |
| Tamoxifen | 57 | 59 | 10 | 11 |
Conclusions
PreM had larger tumors at baseline and were more likely to have received neoadjuvant chemotherapy, suggesting they may have a higher risk of recurrence than PostM.
Clinical trial identification
NCT03155997.
Editorial acknowledgement
The authors would like to thank Garreth Lawrence, who is an employee of Eli Lilly and Company, for their writing and editorial contributions.
Legal entity responsible for the study
Eli Lilly and Company.
Funding
Eli Lilly and Company.
Disclosure
S. Paluch-Shimon: Financial Interests, Personal, Other: Eli Lilly and Company; Financial Interests, Personal, Other: Pfizer; Financial Interests, Personal, Other: Novartis; Financial Interests, Personal, Other: Roche; Financial Interests, Personal, Other: AstraZeneca. H. Lueck: Financial Interests, Personal, Other, Consulting Fees: Eli Lilly and Company; Financial Interests, Personal, Other, Consulting fees: AstraZeneca; Financial Interests, Personal, Other, Consulting fees: GlaxoSmithKlein; Financial Interests, Personal, Speaker’s Bureau: Roche; Financial Interests, Personal, Speaker’s Bureau: AstraZeneca; Financial Interests, Personal, Speaker’s Bureau: Novartis; Financial Interests, Personal, Speaker’s Bureau: Clovis; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Advisory Board: Eli Lilly and Company; Financial Interests, Personal, Advisory Board: Clovis. J. Beith: Other, Personal, Other: Eli Lilly and Company; Other, Personal, Advisory Board: Australian Abemaciclib Advisory Board. E. Tokunaga: Financial Interests, Personal, Invited Speaker: AstraZeneca; Financial Interests, Personal, Invited Speaker: Eli Lilly and Company; Financial Interests, Personal, Invited Speaker: Chugai. T. Forrester: Other, Institutional, Full or part-time Employment: Eli Lilly and Company. R. McNaughton: Other, Institutional, Full or part-time Employment: Eli Lilly and Company. J. Wei: Other, Institutional, Full or part-time Employment: Eli Lilly and Company. N. Harbeck: Financial Interests, Personal, Invited Speaker: AstaZeneca; Financial Interests, Personal, Invited Speaker: Daiichi Sankyo; Financial Interests, Personal, Invited Speaker: Eli Lilly and Company; Financial Interests, Personal, Invited Speaker: Merck Sharp & Dohme; Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Invited Speaker: Pierre Fabre; Financial Interests, Personal, Invited Speaker: Roche; Financial Interests, Personal, Invited Speaker: Pfizer; Financial Interests, Personal, Invited Speaker: Sandoz/Hexal; Financial Interests, Personal, Invited Speaker: SeaGen. All other authors have declared no conflicts of interest.