Prognostic Significance of Lymphocyte-to-Monocyte and Platelet-to-Lymphocyte Ratio in Rectal Cancer: A Systematic Review, Meta-analysis, and Meta-regression.

BACKGROUND

The low lymphocyte-to-monocyte ratio and high platelet-to-lymphocyte ratio have been reported to be poor prognostic indicators in various solid tumors, but the prognostic significance in rectal cancer remains controversial.

OBJECTIVES

We sought to determine the prognostic value of the lymphocyte-to-monocyte ratio and the platelet-to-lymphocyte ratio following curative-intent surgery for rectal cancer.

DATA SOURCES

Following PRISMA guidelines (PROSPERO, ID: CRD42020190880), PubMed and Embase databases were searched through January 2021 including 3 other registered medical databases.

STUDY SELECTION

Studies evaluating the impact of pretreatment lymphocyte-to-monocyte ratio and platelet-to-lymphocyte ratio on overall or disease-free survival in patients undergoing curative rectal cancer resection were selected.

MAIN OUTCOMES MEASURES

The main outcome measures were overall and disease-free survival.

RESULTS

A total of 23 studies (6683 patients) were included; lymphocyte-to-monocyte ratio and platelet-to-lymphocyte ratio were evaluated in 14 and 16 studies. A low lymphocyte-to-monocyte ratio was associated with poorer overall survival (HR, 1.57; 95% CI, 1.29-1.90; p < 0.001) and disease-free survival (HR, 1.29; 95% CI, 1.13-1.46; p < 0.001). However, when the analysis was limited to patients treated with surgery alone or to those with stage I to III tumors, lymphocyte-to-monocyte ratio was not a predictor of overall survival and disease-free survival. The platelet-to-lymphocyte ratio did not predict for overall or disease-free survival, regardless of the treatment modality, studied population, tumor stage, or cutoff value. Finally, a low lymphocyte-to-monocyte ratio, but not a high platelet-to-lymphocyte ratio, was inversely correlated with complete pathologic response rate.

LIMITATIONS

The retrospective nature of most included studies was a limitation.

CONCLUSIONS

Pretreatment lymphocyte-to-monocyte ratio, but not platelet-to-lymphocyte ratio, correlates with tumor response to neoadjuvant chemoradiotherapy and poorer prognosis after curative-intent surgery for rectal cancer, and it potentially represents a simple and reliable biomarker that could help optimize individualized clinical decision-making in high-risk patients.

REGISTRATION

https://www.crd.york.ac.uk/prospero/; ID: CRD42020190880.