Background
ICI showed benefit in PD-L1+ triple-negative BC and solid tumors with hTMB (≥ 10 mut/Mb). There is limited data on ICI treated HR+HER2- BC. Prior work showed that 7% of HR+HER2- BC has hTMB, with an enrichment in lobular carcinoma (15%) and most harboring APOBEC signature (70%). The purpose of this study was to describe real-world time-totreatment-discontinuation (rwTTD) for hTMB HR+HER2- mBC patients (pts) treated with ICI.
Methods
Pts with HR+HER2- mBC from the nationwide (US-based) de-identified Flatiron Health (FH)-Foundation Medicine (FMI) Clinico-Genomic database (CGDB) with genomic profiling by FMI between 01/2011 – 09/2020 and ICI initiation ≥ 6 months (mo) prior to cutoff date were eligible. rwTTD was measured as the difference between the last and first drug episode within a given line of treatment (LOT). LOTs were derived based on FH algorithms. The de-identified EHR data came from ∼280 US cancer clinics (∼800 sites of care). Eligible pts from Mayo Clinic and Duke University were HR+HER2- mBC pts with hTMB tested via FMI between 09/2013 – 07/2020. Clinical data were manually extracted. Similar rwTTD was measured within a given oncologist-defined LOT.
Results
Of 103 eligible pts in CGDB, 20/103 had hTMB. 5/20 pts had ≥ 6 mo on ICI; their TMB was between 16.3-255.8 mut/Mb. 1/5 received ICI with chemotherapy. At Mayo and Duke, there were 37 eligible pts, 8/37 started ICI ≥ 6 mo prior to cutoff date. 4/8 pts had ≥ 6 mo on therapy, their TMB was between 15-74 mut/Mb, and 3/4 had ICI with chemotherapy. Table: 237P
HR+ HER2- hTMB mBC pts who received ICI in Mayo/Duke and CGDB cohorts
Authors:
Chumsri, S, Sammons, S, Alder, L, Sokol, ES, Danziger, NA, Raskina, K, Schrock, AB, Venstrom, JM, Snow, T, Castellanos, EH, Ochuonyo, E, Snider, JW, MGregor, K
Sources:
ESMO Annual Congress