Abstract 221P
Background
Patients with HER2-positive (HER2+) and triple-negative (TNBC) metastatic breast cancer (BC) have a high propensity to develop brain metastases (BrM), but BrM incidence among patients who present with early-stage BC has not been well studied.
Methods
In this population-based cohort study, we used linked administrative databases in Ontario, Canada to identify adult patients diagnosed with stage I-III BC between 2009-2021. Cumulative incidence of surgery and/or radiotherapy for BrM (surrogate for BrM) accounting for competing risk of death, time from primary BC diagnosis to local BrM therapy, and survival time from BrM diagnosis date as stratified by stage and subtype were analyzed using SAS.
Results
Of 91, 517 BC patients, 1, 858 (2%) received local treatment for BrM. Median [IQR] age at BrM diagnosis was 52.5 [45-62] years and initial stage at BC presentation was as follows: stage I (n=272; 15%), stage II (n=767, 41%), and stage III (n=819, 44%). With a median follow-up of 6.4 years [IQR:3.7-9.6], the incidence proportion of BrM was: 0.6% among patients with stage I; 2.4% with stage II; and 6.9% with stage III BC. Subtypes included 406 (22%) hormone-receptor-positive (HR+)/HER2-negative (HER2-), 161 (9%) HER2+/HR+, 126 (7%) HER2+/HR-, 288 (15%) TNBC; unknown subtype, n=877 (47%). Among stage III patients, the incidence proportion of BrM was 16% (TNBC), 13% (HER2+/HR-), 9% (HER2+/HR+), and 4% (HR+/HER2-); corresponding median time from initial BC diagnosis to local BrM therapy was 1.6, 2.0, 2.9, and 3.7 years, respectively. Among patients with stage I-III BC treated locally for BrM, median (m) OS from date of BrM treatment was 5.8 (2-16) months. Survival by BC subtype was as follows, irrespective of initial stage at diagnosis: HER2+ BC, mOS=13.1 (4.6-28) months; HR+/HER2- BC, mOS=5.1 (1.7-15) months; TNBC, mOS=3.6 (1.5-8.7) months.
Conclusions
A high incidence of BrM among patients with stage III BC was identified particularly among those with TNBC or HER2+ BC. The true incidence is likely higher as screening for asymptomatic BrM is not typically performed. In addition, mOS may be over-estimated because untreated patients were not included in this analysis.
Legal entity responsible for the study
K. Jerzak.
Funding
Has not received any funding.
Disclosure
H. Soliman: Non-Financial Interests, Personal, Other, educational events: Elekta ab. M.K. Krzyzanowska: Financial Interests, Invited Speaker: Eisai, Exelixis, Novartis, Eli Lilly (trial funding), Bayer (grant). G. Liu: Financial Interests, Institutional, Research Grant: AstraZeneca, Takeda, Boehringer Ingelheim, Amgen, EMD Serono, Pfizer, Bayer ; Financial Interests, Personal, Invited Speaker, ;ectures, educational events: AstraZeneca, Pfizer, EMD Serono, Takeda; Financial Interests, Personal, Advisory Board: AstraZeneca, Pfizer, EMD Serono, Merck, AbbVie, Jazz, Takeda, Anheart, Roche, BMS, Novartis, Lilly . S. Das: Non-Financial Interests, Personal, Advisory Board: Subcortical Surgery Group; Financial Interests, Personal, Invited Speaker: Congress of Neurological Surgeons, American Association of Neurological Surgeons and American Board of Neurological Surgery.; Financial Interests, Personal, Royalties: Oxford University Press; Non-Financial Interests, Personal, Other, Provincial lead: CNS Oncology at Ontario Health (Cancer Care Ontario). A. Sahgal: Financial Interests, Personal, Other, consulting: arian, Elekta (Gamma Knife Icon), BrainLAB, Merck, ; Non-Financial Interests, Personal, Leadership Role: International Stereotactic Radiosurgery Society (ISRS), AO Spine Knowledge Forum Tumor; Financial Interests, Personal, Other, educational events: AstraZeneca, Elekta AB, Varian, BrainLAB, Accuray, Seagen; Financial Interests, Institutional, Research Grant: Elekta AB, Varian, Seagen Inc., BrainLAB; Financial Interests, Personal, Other, Travel expenses: Elekta, Varian, BrainLAB; Other, Personal, Other, member: Elekta MR Linac Research Consortium; Other, Personal, Leadership Role: Clinical Steering Committee member, and chairs the Elekta Oligometastases Group and the Elekta Gamma Knife Icon Group. K. Jerzak: Financial Interests, Personal, Advisory Board: Amgen, AstraZeneca, Apo Biologix, Daiichi Sankyo, Eli Lilly, Eisai, Genomic Health, Gilead Sciences, Knight Therapeutics, Merck, Myriad Genetics Inc., Pfizer, Roche, Seagen, Novartis, Viatris; Financial Interests, Institutional, Research Grant: AstraZeneca. Eli Lilly, Seagen. All other authors have declared no conflicts of interest.