Abstract 226P
Background
The pattern of metastatic spreading in luminal-like mBC is a current field of research, but few data are available on the evolution of distant involvement after first-line (1L). We aimed to describe the trend in metastatic sites after progression to a 1L.
Methods
The study retrospectively analysed 717 consecutive luminal-like mBC patients (pts) treated at the Oncology Departments of Aviano and Udine, in Italy, between 2008 and 2020, with endocrine therapy (ET) (alone or in combination with cyclin-dependent-kinases 4/6 inhibitors [CDK4/6i]) or chemotherapy (CT) (alone or with ET maintenance). Data were collected at baseline of 1L (BL1) and at progression (PD1). McNemar and Fisher tests were used to explore pairwise differences and associations between newly identified metastatic sites and 1L treatments.
Results
Overall, bone involvement was 71.2% at BL1 and 76.4% at PD1, lung metastasis (mts) was detected in 21.7% of pts at BL1 and in 32.3% at PD1, liver mts in 21.4% at BL1 and in 31.6% at PD1. Central nervous system (CNS) mts were detected in 2.4% of pts at BL1 and in 3.5% at PD1. In the overall population, at paired nominal data test, metastatic sites were consistently increased at PD1 (liver P < 0.0001, bone P = 0.0001, CNS P = 0.0039, bone-only P < 0.0001, lung P < 0.0001, nodes P < 0.0001), as expected. Notably, a similar trend was observed across all 1L treatments, apart for CNS mts in the ET cohort, bone and CNS in both the ET+CDK4/6i and CT subgroups, bone-only disease and CNS mts in CT-ET maintenance group where no significant pairwise changes were highlighted. Analysing newly identified metastatic sites at PD1, pts treated with ET+CDK4/6i had a higher risk of developing new CNS mts (P = 0.018, expected frequency [EF] 1.1 pts vs observed frequency [OF] 3 pts), while pts treated with CT-ET maintenance had a higher risk of developing new lymph node mts (P = 0.014, EF 32.5 pts vs OF 45 pts).
Conclusions
The present study suggested the potential impact of first-line treatment strategies on the evolution of metastatic spreading in luminal-like mBC. Based on these results, future studies will be designed to develop new personalized monitoring strategies.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
A.M.M. Minisini: Other, Personal, Advisory Board: Novartis, MSD, Pierre-Fabre; Financial Interests, Personal, Other, honoraria: Novartis, Merck, MSD, Sunpharma, Pierre-Fabre. L. Gerratana: Other, Personal, Other, personal fees: Eli Lilly, Novartis. F. Puglisi: Financial Interests, Personal, Research Grant, grants/research: AstraZeneca, Eisai, Roche; Other, Personal, Other, honoraria or consultation fees: Amgen, AstraZeneca, Daichii Sankyo, Celgene, Eisai, Eli Lilly, Gilead, GSK, Ipsen, MSD, Novartis, Pierre-Fabre, Pfizer, Roche, Seagen, Takeda, Viatris. All other authors have declared no conflicts of interest.