Page 141 - SRPSKO DRUŠTVO ISTRAŽIVAČA RAKA

SDIRSACR Oncology Insights

SESSION 9

CLINICAL ONCOLOGY - BRIDGING PATIENTS AND RESEARCHERS

P46

Efficacy of Neoadjuvant Immune Checkpoint Inhibitors in Colorectal Cancer: A Retrospective Study

Nikita Volkov, Vladimir Moiseyenko, Vitaliy Egorenkov, Aleksey Bogdanov, Fedor Moiseyenko, Ikram Aliev, Azad
Nazmiev, Ani Oganesyan, Daria Barsova, Maria Krasavina

N.P Napalkov Saint Petersburg Clinical Research and Practical Centre for Specialized Types of Medical Care (Oncological), Saint
Petersburg, Russia

Keywords: colorectal cancer, neoadjuvant immunotherapy, immune checkpoint inhibitors, MSI-H, pathological
complete response

Introduction: This retrospective study evaluated the efficacy of neoadjuvant immune checkpoint inhibitors (ICIs) in
patients with localized and locally advanced colorectal cancer (CRC). The research focused on microsatellite instability-
high (MSI-H) tumors, which are known to respond well to immunotherapy. The study aimed to assess clinical and
pathological responses, toxicity, and survival outcomes in this patient population.
Materials and Methods: From October 2020 onwards, 220 patients with localized or locally advanced CRC were screened,
of whom 36 (16.4%) had MSI-H tumors. Among these, 24 patients (66.7%) received neoadjuvant immunotherapy, while
11 underwent surgery without neoadjuvant treatment, and 1 was excluded due to severe comorbidities. The cohort
included patients with varying tumor stages (T2–T4, N0–N2) and locations (right/left colon, rectum). Immunotherapy
regimens included nivolumab (54.2%), pembrolizumab (29.2%), prolgolimab (4.2%), ipilimumab+nivolumab (8.3%),
and FOLFOX+nivolumab (4.2%). The median number of cycles administered was 5 (range: 2–31).
Results: Among all 24 treated patients, the objective response rates were: complete response (CR) in 12.5%, partial
response (PR) in 33.3%, and stable disease (SD) in 45.8%. One patient (4.2%) experienced progressive disease (PD).
Of the 16 patients who underwent surgery, 50% achieved a pathological complete response (pCR). Toxicity was
manageable, with grade 1–2 adverse events occurring in 25% of patients, while one patient died due to severe toxicity
(grade 5). At a median follow-up of 14.4 months, median progression-free and overall survival were not reached, with
only one case of disease progression post-surgery.
Conclusions: Neoadjuvant immunotherapy demonstrated high efficacy in MSI-H CRC, with a notable pCR rate of 50%
among operated patients. However, challenges remain, including the need for faster MSI testing and unresolved
questions regarding the necessity of surgery for patients with clinical CR and the role of adjuvant therapy. These
findings support further investigation into optimizing treatment protocols for this patient subset.

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