Impact of Neoadjuvant Immunotherapy in Localized Rectal Cancer. A Systematic Review

Area of Science:

• Oncology
• Gastroenterology
• Immunotherapy

Background:

• Current treatments for locally advanced rectal cancer (LARC) involve surgery and radiation, often impacting quality of life.
• Anti-PD1 immunotherapy has demonstrated high clinical complete response rates in MSI-H LARC, offering a less toxic alternative.
• The integration of immunotherapy into neoadjuvant treatment for both MSI-H and MSS LARC warrants a comprehensive safety and efficacy review.

Purpose of the Study:

• To assess the safety, toxicity, pathological impact, and long-term benefits of neoadjuvant immunotherapy in LARC.
• To systematically review existing literature on immunotherapy for both MSI-H and MSS LARC.
• To identify current gaps in knowledge and guide future research directions.

Main Methods:

• A systematic review following PRISMA guidelines was conducted.
• Twelve published studies encompassing 547 patients were analyzed.
• Data extraction included study characteristics, treatment protocols, outcomes, and quality assessment using MINORS and RoB2 tools.

Main Results:

• R0 resection rates were high across both MSS (70%-100%) and MSI-H (80%-100%) cohorts.
• Pathological complete response (pCR) rates were 25%-50% for MSS and 50%-60% for MSI-H.
• While Grade 3-4 adverse events varied, immune-related events were generally below 10%.

Conclusions:

• Neoadjuvant immunotherapy shows potential for LARC, particularly in MSI-H cases, with high response rates.
• The efficacy and optimal use of immunotherapy in MSS LARC remain uncertain, necessitating further research.
• Phase III trials and translational research are crucial to establish immunotherapy's role in MSS rectal cancer treatment.