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.