Abstract 122TiP
Background
PD-1 monoclonal antibody therapy has demonstrated significant efficacy in DNA mismatch repair-deficient or microsatellite instability-high (dMMR/MSI-H) colorectal cancer (CRC). Notably, neoadjuvant immunotherapy has shown promising pathological complete response (pCR) rates in these patients. However, radical resection in distal rectal cancer (RC) may lead to functional impairments and psychological distress. The feasibility and safety of a watch and wait approach in patients with early stage and locally advanced (stage I-III) dMMR/MSI-H distal RC achieving clinical complete response (cCR) after PD-1 monoclonal antibody therapy remain uncertain.
Trial design
The BASKET study is an open-label, multicenter, prospective phase II trial conducted in China. Patients with stage I-III dMMR/MSI-H distal RC received neoadjuvant immunotherapy with 200 mg sintilimab (PD-1 monoclonal antibody) intravenously on day 1 of each 3-week cycle for 6 cycles. Patients achieving cCR after PD-1 monoclonal antibody therapy were enrolled and initiated a watch and wait approach. This study is the first prospective evaluation of the efficacy and safety of watch and wait in these patients. Precise clinical evidence from this study will inform individualized precision treatment for distal RC patients, aiming to preserve organ function and improve quality of life. Key inclusion criteria comprised tumor biopsy confirmed dMMR by immunohistochemical (IHC) staining or MSI-H by next-generation sequencing, MRI-identified tumor located below the peritoneal reflection, and clinical staging TxNxM0. cCR was assessed by enhanced CT/MRI and confirmed by biopsy. Stage IV distal RC, multiple CRC, active autoimmune diseases, and long-term corticosteroid use were among the main exclusion criteria. A total of 47 patients are planned for enrollment. As of May 1, 2024, 10 patients have been enrolled. The study is registered with ClinicalTrials.gov (NCT04643041) and ongoing.
Clinical trial identification
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.