A Study to Investigate Tislelizumab (BGB-A317) Versus Placebo in Combination With Concurrent Chemoradiotherapy in Participants With Localized Esophageal Squamous Cell Carcinoma

OS is defined as the time from the date of randomization to the date of death due to any cause. OS was estimated using the Kaplan-Meier method.

The EORTC-QLQ-OES18 is the specific esophageal symptoms module of the QLQ-C30. QLQ-OES18 is comprised of 18 questions grouped into 4 multi-item subscales: Dysphagia (3 items), Eating (4 items), Reflux (2 items), and Pain (3 items) and 6 single item subscales (saliva swallowing, choking, dry mouth, taste, coughing, and talking). Participants indicate the extent to which they have experienced symptoms on a scale from 1 (Not at all) to 4 (Very much). Scores are calculated and transformed to a scale from 0 to 100; higher scores indicate a higher level of symptomatology or problems.

The EORTC QLQ-30 contains 30 questions that incorporate 5 functional scales (physical functioning, role functioning, emotional functioning, cognitive functioning, and social functioning), 1 global health status scale, 3 symptom scales (fatigue, nausea and vomiting, and pain), and 6 single items (dyspnea, insomnia, appetite loss, constipation, diarrhea, and financial difficulties). The participant answers questions about their health during the past week. There are 28 questions answered on a 4-point scale where 1 = Not at all (best) and 4 = Very Much (worst) and 2 global health quality of life (QOL) questions answered on a 7-point scale where 1 = Very poor and 7 = Excellent. Raw scores are transformed into a 0 to 100 scale via linear transformation. Higher scores in GHS and functional scales indicate better quality of life. Lower scores in symptom scales indicate better quality of life.

ORR is defined as the percentage of participants who had complete response (CR) or partial response (PR) as assessed by BIRC per RECIST v1.1.

Tumor assessments were made using computed tomography (CT) scans or using magnetic resonance imaging (MRI).

CR: Disappearance of all target lesions and non-target lesions, no new lesions, and normalization of tumor marker level. All lymph nodes must be nonpathological in size (<10 mm short axis).

PR: At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters and/or persistence of one or more non-target lesion(s) and/or maintenance of tumor marker level above the normal limits.

DOR is defined as the time from the first occurrence of a documented objective response to the time of relapse, as determined by the BIRC per RECIST v1.1, or death from any cause, whichever occurs first. DOR was estimated using the Kaplan-Meier method.

An adverse event (AE) is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study treatment, whether considered related to study treatment or not. A TEAE is an AE that had an onset date or a worsening in severity from baseline on or after the first dose of study treatment and up to 30 days following study treatment discontinuation or initiation of new anticancer therapy, whichever occurred first.

A serious adverse event (SAE) is any untoward medical occurrence that, at any dose:

• Resulted in death
• Was life-threatening
• Required hospitalization or prolongation of existing hospitalization
• Resulted in disability/incapacity
• Was a congenital anomaly/birth defect
• Was considered a significant medical AE by the investigator based on medical judgement.