Jiménez‐Fonseca, Paula

366 Background: While improved survival has been previously demonstrated, the impact of immunotherapy on HRQoL in ESCC has not been well examined. Traditional PRO-based analyses in oncology trials, such as time to deterioration (TTD) and mixed models for repeated measures (MMRMs), are limited by discounting recurrent PRO events. Thus, we applied a 3-component joint model (JM) framework to define more clinically interpretable associations between patient-reported symptoms, treatment effects, and OS among subgroups of patients with ESCC from RATIONALE-306, which met its primary endpoint, with PD-L1 expression of ≥1%, ≥5%, and ≥10%. Methods: The final analytic sample included 226 patients in the tislelizumab + chemotherapy arm (T+C), 242 in the placebo + chemotherapy arm (P+C) for PD-L1 ≥1%, 113 in the T+C arm and 103 in the P+C arm for PD-L1 ≥5%, and 168 in the T+C arm and 178 in the P+C arm for PD-L1 ≥10%.From EORTC QLQ-C30 and OES18, 7 keysymptom domains were modeled (GHS, physical functioning, fatigue, dysphagia, pain, reflux, dietary restrictions). PRO data were collected at baseline and at every treatment cycle (up to 6 cycles), then every other cycle, and at safety follow-up, and change from baseline (CFBL) was analyzed. The joint model comprised three components: 1) linear mixed model predicting CFBL symptom scores; 2) Cox proportional hazard model (CPH) for time to OS; and 3) frailty (random effects for recurrent deterioration events [RDEs]) CPH model for time to PRO-based RDEs. Osoba (1998) 10-point threshold was used to define RDEs. Results: Adjusted completion rates were >90% in the ITT population for both arms. Significant T+C treatment effects wereobserved for physical functioning in PD-L1 ≥5% ( P =0.0476), and pain in PD-L1 ≥1% ( P =0.0028) and PD-L1 ≥5% ( P =0.0149) subgroups, but not in PD-L1 ≥10%. For other 5 symptoms (ie, GHS, fatigue, reflux, dysphagia, dietary restrictions), there were no statistically significant differences between treatment arms. However, T+C was associated with significant reductions in the risk of death across all 7 key symptoms and PD-L1 subgroups. As one example, with respect to interaction between pain and OS, T+C was associated with a 22% (HR, 0.78 [95% CI, 0.652-0.931]), 33% (HR, 0.67 [95% CI, 0.515-0.860]), and 47% (HR, 0.50 [95% CI, 0.344-0.720]) reduction in the risk of death in PD-L1 ≥1%, ≥5%, and ≥10%, respectively compared with P+C. Conclusions: In this analysis, the addition of tislelizumab to chemotherapy was associated with significantly less deterioration in multiple PRO symptoms including physical functioning and pain, alongside a lower risk of death, after adjusting for recurring deterioration events using a frailty model across multiple PD-L1 expression subgroups.

340 Background: TIS, an anti-programmed cell death protein 1 (PD-1) antibody, + chemo as 1L therapy demonstrated statistically significant and clinically meaningful improvement in overall survival (OS) vs PBO + chemo in patients with advanced or metastatic ESCC (hazard ratio [HR] 0.66 [95% confidence interval (CI) 0.54, 0.80]; P< 0.0001), with a manageable safety profile, at interim analysis of the phase 3, double-blind RATIONALE-306 study (NCT03783442). Here, we report data from the non-Asia subgroup (Europe, Northern America, and Oceania). Methods: Adults with advanced or metastatic ESCC, with no prior systemic treatment for advanced disease were randomized 1:1, (stratified by region, prior definitive therapy, and investigator [INV]-chosen chemo) to receive TIS 200 mg intravenously (IV) once every 3 weeks (Q3W) (Arm A) or PBO IV Q3W (Arm B), with platinum + fluoropyrimidine, or platinum + paclitaxel until disease progression by INV per RECIST v1.1, intolerable toxicity, or withdrawal. The primary endpoint was OS in the intent-to-treat population. Secondary endpoints included: progression-free survival (PFS), objective response rate (ORR), and duration of response (DoR) by INV per RECIST v1.1; OS in the programmed death-ligand 1 score ≥10%; and safety. Results: Of 649 randomized patients, 163 (25.1%) were from the non-Asia subgroup (Arm A, n = 83; Arm B, n = 80). At data cutoff (Feb 28, 2022), the median study follow-up time in the non-Asia subgroup was 16.0 months (mo) in Arm A vs 8.4 mo in Arm B. OS (median 16.3 vs 9.0 mo; unstratified HR 0.66 [95% CI 0.45, 0.96]) and PFS (median 7.7 vs 5.5 mo; unstratified HR 0.59 [95% CI 0.41, 0.83]) were improved in Arm A vs Arm B, respectively. Arm A had higher ORR (61.4% vs 41.3%, odds ratio 2.27 [95% CI 1.21, 4.25]) and longer median DoR (7.1 mo [95% CI 5.6, 9.6] vs 5.7 mo [95% CI 3.8, 8.3]) than Arm B. More patients in Arm A vs Arm B experienced ≥1 treatment-related adverse event (TRAE; 94.0% vs 88.5%), serious TRAEs (25.3% vs 17.9%), and discontinuation due to treatment-emergent AEs (42.2% vs 35.9%, respectively). Similar proportions of patients in Arm A vs Arm B had ≥grade 3 TRAEs (56.6% vs 52.6%), and TRAEs leading to death (1.2% vs 1.3%), respectively. Conclusions: In the non-Asia subgroup, 1L TIS + chemo showed a clinically meaningful improvement in OS vs PBO + chemo in patients with advanced or metastatic ESCC, with a manageable safety profile, consistent with published results in the overall population. Clinical trial information: NCT03783442 .

Abstract Context SDHB mutations are found in an increasing number of neoplasms, most notably in paragangliomas and pheochromocytomas (PPGLs). SDHB-PPGLs are slow-growing tumors, but ∼50% of them may develop metastasis. The molecular basis of metastasis in these tumors is a long-standing and unresolved problem. Thus, a better understanding of the biology of metastasis is needed. Objective This study aimed to identify gene methylation changes relevant for metastatic SDHB-PPGLs. Design We performed genome-wide profiling of DNA methylation in diverse clinical and genetic PPGL subtypes, and validated protocadherin γ-C3 (PCDHGC3) gene promoter methylation in metastatic SDHB-PPGLs. Results We define an epigenetic landscape specific for metastatic SDHB-PPGLs. DNA methylation levels were found significantly higher in metastatic SDHB-PPGLs than in SDHB-PPGLs without metastases. One such change included long-range de novo methylation of the PCDHA, PCDHB, and PCDHG gene clusters. High levels of PCDHGC3 promoter methylation were validated in primary metastatic SDHB-PPGLs, it was found amplified in the corresponding metastases, and it was significantly correlated with PCDHGC3 reduced expression. Interestingly, this epigenetic alteration could be detected in primary tumors that developed metastasis several years later. We also show that PCDHGC3 down regulation engages metastasis-initiating capabilities by promoting cell proliferation, migration, and invasion. Conclusions Our data provide a map of the DNA methylome episignature specific to an SDHB-mutated cancer and establish PCDHGC3 as a putative suppressor gene and a potential biomarker to identify patients with SDHB-mutated cancer at high risk of metastasis who might benefit from future targeted therapies.