Predicting complete response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer: The role of baseline volumetric 18F-FDG PET/CT parameters and inflammatory markers.

Objectives: We evaluated the influence of baseline volumetric 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) parameters and inflammatory prognostic markers on complete response (CR) in patients with locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (nCRT).

Materials and methods: In total, 90 patients with LARC, including those with and without CR, were evaluated based on baseline volumetric PET/CT parameters, such as maximum standard uptake value, metabolic tumor volume (MTV), tumor lesion glycolysis, and inflammatory prognostic markers, including the lymphocyte-to-monocyte ratio, platelet-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte ratio.

Results: Of the 90 patients, 62 (68.9%) were male and 28 (31.1%) were female. The median age was 61 (31-81) years. A complete response was observed in 20 (22%) patients following nCRT. Of these, 5 demonstrated a clinical complete response, whereas 15 exhibited a complete response after surgery. A low pretreatment PLR, low MTV levels, and stage 2 disease were identified as significant predictors of complete response. The optimal cutoff values were 16.5 for MTV (sensitivity 80%, specificity 62%) and 121 for PLR (sensitivity 73%, specificity 65%).

Conclusion: Our findings suggest that stage 2 disease, low pretreatment MTV, and low PLR levels may be predictive of a CR to nCRT in patients with LARC.