Sintilimab (One Anti-PD-1 Antibody) Plus Low-dose Bevacizumab for ctDNA-level-relapse and Clinical-relapse Glioblastoma

This is an ongoing Phase 2, open-label, single-center, non-randomized study of sintilimab (one anti-PD-1 antibody same as nivolumab approved in China) plus bevacizumab administered in a low dosage schedule in adult (≥ 18 years) participants with a clinical relapse or circulating tumor DNA (ctDNA)-level relapse of glioblastoma (GBM). This study has two non-comparative study groups. Both cohorts will receive the same study drug sintilimab 200mg and bevacizumab 3mg/kg every 3 weeks. A stringent two-step non-randomized process will be used to assign participants to one of the study groups. Neither participants nor doctors but the researcher can choose which group participants are in. No one knows if one study group is better or worse than the other. 60 total participants are expected to participate in this study (30 participants in each cohort). Grouping process: After enrollment, under the standard of care, participants will receive regular tumor in situ fluid (fluid within the surgical cavity, TISF) sampling for ctDNA analysis and recceive regular MRI. The researcher will study the TISF ctDNA and imaging dynamics to determine whether the tumor reaches to ctDNA-level (Cohort 1) or clinical relapse (Cohort 2). At the first step, all timely identified as ctDNA-level relapse tumors will be assigned into the Cohort 1 and receive the study drug immediately, those failed to be timely identified will be assigned into the Cohort 2 and receive the study drug after the clinical relapse. At the second step, once either group reaches the target number, the new participants will be all assigned into the other Cohort.