Abstract 16P
Background
pET in HR+/HER2- BC is a valuable tool for guiding treatment decisions, by offering real-time assessment of endocrine sensitivity. Changes in Ki67 induced by pET serve as a biomarker for assessing the need for adjuvant chemotherapy. We evaluated baseline clinicopathological and molecular features associated with Ki67 after short pET.
Methods
A retrospective population-cohort involving 245 patients (pts) with HR+ HER2- EBC treated between 2014 and 2023 with pET for 2 to 12 weeks prior to surgery at the Hospital Clinic de Barcelona was analyzed. Data included age, stage, menopausal status (MS), body mass index (BMI), hormone receptors intensity, tumor infiltrate lymphocytes (TILS), PAM50 intrinsic subtype (IS) calculated by Prosigna, risk of recurrence (ROR), baseline and post treatment Ki67 and treatment strategies. pET response was defined as a complete cell cycle arrest (CCCA) (Ki67≤2.7%). Chi-square test, uni- and multi-variable logistic regression models identified variables associated with pET response. BMI, estrogen receptor, MS, baseline Ki67, TILs, ROR and IS were included in the multivariate analysis.
Results
Among 245 pts who underwent pET, with a median baseline Ki67 of 12% (1 – 80%), 47.6% reached CCCA. CCCA was significantly higher in postmenopausal than in premenopausal pts (56.3% vs 16.3%, p<0.001). According to IS, 44.1% (26) of Luminal A tumors had CCCA vs 26.5% in Luminal B (p=0.092), no non-luminal patients were identified. Regarding ROR, CCCA was reached in 50.0%(17), 37.5%(12) and 22.2%(6) of patients with low, intermediate and high risk, respectively (p=0.084). Higher baseline TILs were associated with lower CCCA (odds ratio [OR]=0.92; p=0.006). As for treatment, we found no differences in response by treatment duration, <4 vs 4 – 12 weeks (OR=1.16; p=0.729). Yet, tamoxifen did significantly worse than aromatase inhibitors, (OR=0.18; p<0.001). In the multivariable analysis, only IS (OR=10.31; p=0.046) was associated with CCCA, ROR as a continuous score was (OR=0.92; p= 0.040).
Conclusions
IS and ROR are the strongest predictor of pET response. Combining these results with other risk assessment strategies could better individualize treatment strategies.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
F. Schettini: Financial Interests, Personal, Invited Speaker: Novartis, Gilead, Daiichi-Sankyo; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Other, Travel expenses: Novartis, Gilead, Daiichi-Sankyo. O. Martínez-Sáez: Financial Interests, Personal, Invited Speaker: Novartis, Eisai; Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Personal, Other, Travel expenses: Roche; Financial Interests, Personal, Other, Medical advisory: Reveal Genomics. I. Garcia Fructuoso: Financial Interests, Personal, Invited Speaker, And travel expenses: Novartis; Financial Interests, Personal, Invited Speaker, And Travel expenses: Daiichi Sankyo; Financial Interests, Personal, Invited Speaker: Eisai; Financial Interests, Personal, Other, Travel expenses: Gilead, Lilly. T. Pascual: Financial Interests, Personal, Invited Speaker: Pfizer/ AstraZeneca / Veracyte / Novartis; Financial Interests, Personal, Advisory Board: Roche/Genentech, Novartis. M.J. Vidal Losada: Financial Interests, Personal, Advisory Board: Novartis/Pfizer, Roche, Pfizer, AstraZeneca/Daiichi Sankyo; Financial Interests, Personal, Invited Speaker: Novartis/Pfizer, Roche/Genentech, AstraZeneca/Daiichi Sankyo, Gilead Sciences, Veracyte, Guardanthealth; Financial Interests, Personal, Other, Travel, Accommodations, expenses: Pfizer; Financial Interests, Personal, Other, Travel, Accommodations, Expenses: Gilead Sciences. F. Brasó-Maristany: Financial Interests, Personal, Full or part-time Employment, part time employment: Reveal Genomics SL; Financial Interests, Personal, Other, Patents filed: EP23382703 and EP23383369: Reveal Genomics SL; Financial Interests, Personal, Other, Patents filed: PCT/EP2022/086493, PCT/EP2023/060810: Fundació de Recerca Clínic Barcelona-Institut d'Investigacions Biomèdiques August Pi i Sunyer. A. Prat: Financial Interests, Personal, Invited Speaker: Roche, 1TRIALSP, S.L.; Financial Interests, Personal, Invited Speaker, Lecture fees: Novartis, Daiichi Sankyo; Financial Interests, Personal, Advisory Board, Advisory role/consultancy: Novartis, Pfizer, Peptomyc; Financial Interests, Institutional, Invited Speaker, Clinical trials: Daiichi Sankyo; Financial Interests, Institutional, Other, Contracted research: Boehringer, Medica Scientia inno. Research; Financial Interests, Personal, Advisory Board: AstraZeneca, Reveal Genomics; Financial Interests, Personal, Member of Board of Directors, Leadership role: Reveal Genomics, SL.; Financial Interests, Personal, Stocks/Shares: Reveal Genomics; Financial Interests, Personal, Royalties: Reveal Genomics, International Oncology Bureau, S.L.,; Financial Interests, Institutional, Invited Speaker: Roche, AstraZeneca, Novartis; Financial Interests, Personal and Institutional, Invited Speaker: Daiichi Sankyo; Financial Interests, Institutional, Funding: Reveal Genomics; Non-Financial Interests, Institutional, Other, Leadership roles: Patronage committee: Actitud Frente al Cáncer Foundation; Non-Financial Interests, Personal, Other, Asociación Española de Investigación sobre el Cáncer: ASEICA; Non-Financial Interests, Personal, Other, Research Foundation that gives grants to researchers: FERO. M. Munoz: Financial Interests, Personal, Expert Testimony: Roche, Novartis; Financial Interests, Personal, Other, International conference travel grants: Roche, Pfizer, Lilly, Gilead; Financial Interests, Personal, Advisory Board: Pierre Fabre, Seagen, AstraZeneca. All other authors have declared no conflicts of interest.