Abstract 45P
Background
The standard approach for selected patients (pts) with locally advanced colon cancer (LACC) is surgery with adjuvant chemotherapy. Several studies have shown that MSI/dMMR CRC pts tend to be more responsive to anti-PD1 immune checkpoint inhibitors however there is ony a few studies evaluated preoperative immunotherapy in pts with LACC. However, there was no information about the efficacy of prolgolimab in this setting.
Methods
We conducted the II phase non-randomized open-label clinical trial. Inclusion criteria were histologically verified, MSI/dMMR, clinical T3(with extramural extension ≥ 5mm)-T4NanyM0 CRC. Pts were treated with prolgolimab (1 mg/kg) every two weeks and underwent surgery after 6 months of immunotherapy (12 cycles). The primary endpoint was pathologic and durable (>6 months) clinical complete response (pCR + cCR) rate. Secondary endpoints included tumor regression grade by Mandard (TRG), major pathologic response (MPR) rate, objective response rate (ORR), disease free survival (DFS), overall survival (OS), safety. Here we present interim analysis of safety and pathologic response data.
Results
A total of 26 pts began treatment with prolgolimab from August, 2022 to February, 2024. Immune-related adverse effects of grade 3-4, were recorded in 1 (3,8%) pt (autoimmune hepatitis of grade 4). 4 (15,4%) pts had adverse effects of grade 1-2: autoimmune thyroiditis, diarrhea. With median follow-up time 5 months 15 pts completed neoadjuvant therapy: 9 underwent surgery, 2 pts refused, 1 pt died suddenly of cardiac arrest and 11 pts are still on treatment. Among 9 operated pts 7 (78%) pts had TRG 1 (pCR), 2 (22%) pts had TRG 2 (100% MPR).Overall cCR+pCR is 56% (9 of 16 pts), during the treatment progression was not observed.
Conclusions
Prolgolimab is safe and demonstrate high activity in MSI/dMMR LACC. Further survival analysis highlights the role of immunotherapy in neoadjuvant setting.
Legal entity responsible for the study
Blokhin Medical Center of Oncology.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.