To differentiate prognostic groups in patients with ER+HER2neg breast cancer (BC) Ki67 thresholds of 14% and 20% have been defined. However, most clinical research has been driven by outcomes of invasive carcinoma of no special type, with ILC underrepresented. Previous studies suggested a 4% Ki67 cut-off to distinguish prognostic groups in the ILC population
Retrospective study including early-stage BC patients (pts) with ER+HER2neg pure ILC diagnosed from 2010 to 2015 at 2 sites (Vall d’Hebron University Hospital and Institut Català d’Oncologia-Hospitalet) and with tumor sample available. Local and central Ki67 values from surgical specimen (or initial biopsy for neoadjuvant treated-pts) were obtained. The primary endpoint were disease free-survival (DFS) and overall survival (OS). The log-rank statistic was used to select the optimal Ki67 cut-off.
Overall, 275 pts were identified, median age: 61 years, postmenopausal (71.4%), stage I-II (73.4%), progesterone receptor (PgR) (78%), histology grade 1-2 (92.7%) and 34.5% receiving adjuvant chemotherapy. The median Ki67 values with local (n=257) and central (n=164) assessment were 12% and 13%, respectively (correlation= 0.63). Several factors such as pT, stage, PgR, and grade were associated with DFS and OS in the univariable analysis. Local Ki67 as a continuous variable was not associated with DFS (p=0.75), but showed a trend for association with OS (p=0.06). With local Ki67 values, cut-off from 10% to 24% showed similar results (using 10% as a cut-off, OS HR: 1.82, 95%CI 1.10-3.01, p=0.02). Central Ki67 as a continuous variable was not statistically associated with DFS (p=0.09) or OS (p=0.33). However, the optimal cut-off was identified at 10% allowing to separate two groups with different prognostic (Ki67% 10% vs <10%, HR: 2.37, 1.09-5.19, p=0.03).
In our series of ILC median Ki67 was around 12%, with moderate concordance between local and central assessments. Lower Ki67 cut-off (10%) than those reported in overall population may better distinguish prognostic groups in ILC pts.
Vall d'Hebron Institute of Oncology (VHIO).
Has not received any funding.
M. Bellet-Ezquerra: Financial Interests, Personal, Advisory Board: Pfizer, Novartis, Lilly, Stemline-Menarini; Other, Speaker'sBureau and Travel Expenses: Pfizer; Other, Speaker's Bureau: Novartis, Lilly. G. Villacampa: Financial Interests, Personal, Invited Speaker, Invited speaker in a course: MSD; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Invited Speaker, Invited speaker in an internal training: Pierre Fabrer, GSK; Financial Interests, Personal, Invited Speaker, Internal discussion about the interpretation of some published results: Pfizer; Financial Interests, Personal, Other, Collaborations with specific projects: Reveal Genomics. E. Zamora: Financial Interests, Personal, Invited Speaker, Review session for medical oncologists: Eisai, Lilly; Other, Registration to ESMO Congress 2022 (virtual): Novartis; Other, Registration to: Eisai. C. Saura Manich: Financial Interests, Personal, Advisory Board: AX'Consulting, AstraZeneca, Daiichi Sankyo, Eisai, Exact Sciences, Exeter Pharma, F. Hoffmann - La Roche Ltd., Gilead, ISSECAM, Lilly, MediTech, Medical Statistics Consulting, Merck Sharp & Dohme, Novartis, Pfizer, Philips, Piere Fabre, PintPharma, Puma, Roche Farma, Sanofi-Aventis, Seagen, Solti, Zymeworks, Pharmalex Spain SLU; Financial Interests, Personal, Expert Testimony: AX's Consulting SARL, Boehringer Ingelheim, Bristol Meyers Squibb, INDITEX, Merck Sharp & Dohme España, Novartis, SACE Medhealth SL, Simon Kucher &Partners SL, Genentech, Innoup, Millenium, Sanofi, Seattle Genetics; Financial Interests, Personal, Other, SC: Byondis B.V., German Breast Group, Glaxo, International Breast Cancer Study Group (IBCSG), Macrogenics, Medsir, Menarini, Merus, Merus, Netherlands Cancer Institute (NKI), Queen Mary (University of London), Seagen, Synthon Biopharpaceuticals; Financial Interests, Institutional, Research Grant: AstraZeneca, Bayer Pharma, Boehringer Ingelheim, Bristol Myers Squibb (BMS), Cytomx Therapeutics, Daiichi Sankyo, Eli Lilly and Company, F. Hoffmann-La Roche Ltd., Genentech, Glaxosmithkline, Immunomedics, Innoup Farma, International Breast Cancer Study Group (IBCSG), Macrogenics, Medica Scientia Innovation Research, Menarini Ricerche, Merus, Novartis, Pfizer, Puma, Roche, Sanofi-Aventis, Seattle Genetics, SOLTI; Financial Interests, Institutional, Invited Speaker: Byondis B.V.; Non-Financial Interests, Member: Spanish Society of Medical Oncology (SEOM), American Society for Clinical Oncology (ASCO), SOLTI group (Academic research group in breast cancer), Geicam (Spanish Breast Cancer Research Group), American Association for Cancer Research (AACR). S. Pernas Simon: Financial Interests, Personal, Advisory Board: Seagen, AstraZeneca- Daiichi Sankyo, Pierre-Fabre, Pfizer; Financial Interests, Personal, Invited Speaker: Lilly, Novartis, Eisai, Roche; Financial Interests, Institutional, Invited Speaker: Astra-Zeneca, Novartis, Daiichi Sankyo; Non-Financial Interests, Invited Speaker: SOLTI. P.G. Nuciforo: Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Advisory Board: MSD Oncology, Bayer; Financial Interests, Personal, Other, Consultant: Targos Molecular Pathology GmbH. All other authors have declared no conflicts of interest.