1503P Prevalence and clinical characteristics of metastatic synovial sarcoma (mSS) patients with tumours expressing NY-ESO-1 antigen (NY+) and who are HLA-A*02:01, *02:05 or *02:06 allele positive (HLA+): Cohort study from the French sarcoma group

Letetresgene autoleucel is a genetically engineered NY-ESO-1–specific TCR T-cell therapy being investigated in mSS patients whose tumours express the NY-ESO-1 antigen and who are HLA-A*02:01, HLA-A*02:05, or HLA-A*02:06 allele positive (NY+/HLA+). Our objective was to understand prevalence & clinical characteristics of NY+/HLA+ nationally representative population. This retrospective cohort study French national reference centres. Adult with histologically confirmed diagnosis ≥1 Jan 2000 registered sarcoma database (NETSARC+) available FFPE archival primary tumour samples data were included. Tumour examined for expression (by IHC, NY+ defined as ≥30% cells staining 2+/3+ stain intensity) HLA sub-type RNA-seq using Optitype genotyping algorithm). 109 met criteria; 106, status 94, both statuses 91 patients. 61% similar among HLA+ HLA- populations (56% 62%, resp) by line systemic treatment (in 1L: 60%, 2L: 59%). Mean age 11.0 years (NY+ 10.4 yrs, NY- 12.0 p=0.151). 45% (43% 49%, 44%, 45%). Overall, 25% (23/91) dual (NY+/HLA+, 23%, 22%). Characteristics vs. and/or reported table.Table: 1503PPatient characteristicsAll (n=109), includes 17 missing NY/HLA dataNY+/HLA+ (n=23) samplesNY- (n=69) samplesFisher exact test (p>0.05 = NS)Male55%61%58%NSPrimary location limbs60%87%49%p=0.003Primary size ≥90 mm57%70%56%NSDiagnosed metastatic disease ≤55 yrs age71%78%68%NSSite first metastasis lung only70%91%67%p=0.029Only one site87%96%86%NSDiagnosed ≤ year 201045%65%41%NSTime from localised ≤12 months29%41%29%NS Open table new tab Nationally profile previously unknown have been documented this study. Among samples, no relationship observed between NY-ESO sub-type, treatment.