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Role of Neoadjuvant Immune Checkpoint Inhibitors in Locally Advanced Rectal Cancer: A Systematic Review of Currently
Milton Mui1,2, Joseph Ch Kong1,3, Michael Michael2,4
1Department of Cancer Surgery, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
Background:
During the past few decades, the standard of care for locally advanced rectal cancer, involving neoadjuvant chemoradiation followed by surgery, has been associated with a pathological complete response rate of only 10% to 20%. Combination therapy with immune checkpoint inhibitors may improve treatment response.
Objective:
This systematic review examines the current evidence regarding neoadjuvant immune checkpoint inhibitors in locally advanced rectal cancer in terms of treatment efficacy, impact on surgical outcomes, and potential adverse events.
Data Sources:
A literature search was conducted using the Ovid MEDLINE, Embase, Web of Science, and Cochrane Library databases from the start of database records to October 31, 2024.
Study Selection:
All studies that reported outcomes in patients with locally advanced rectal cancer who received immune checkpoint inhibitors as part of their neoadjuvant treatment were included for examination.
Main Outcome Measures:
Primary outcome was pathological complete response rate. Secondary outcomes were major pathological response rate, clinical complete response rate, complete response rate, R0 resection rate, and sphincter preservation rate. Safety data were included where available. Potential biomarkers of treatment response were identified.
Results:
Twelve studies were reviewed. All were prospective phase I/II clinical trials. The overall pathological complete response rate ranged from 25% to 62.5% (50% for deficient mismatch repair/high microsatellite instability; 25%-62.5% for proficient mismatch repair/microsatellite stable). The clinical complete response rate ranged from 10.9% to 100% (56%-100% for deficient mismatch repair/high microsatellite instability; 16.4%-48% for proficient mismatch repair/microsatellite stable). The complete response rate ranged from 44% to 75% (75% for deficient mismatch repair/high microsatellite instability; 44%-56.5% for proficient mismatch repair/microsatellite stable). The R0 resection rate ranged from 94% to 100% and the sphincter preservation rate ranged from 59.4% to 100%. The majority of adverse events were of grades 1 and 2.
Limitations:
Our review was limited by a small number of mostly single-arm studies with a lack of long-term survival outcomes, as well as marked clinical and methodological heterogeneity among included studies.
Conclusions:
Combination therapy with immune checkpoint inhibitors in locally advanced rectal cancer appears to improve treatment response, but high-level evidence and long-term data are still lacking.
