Assessing the role of colonic and other anatomical sites uptake by [18 F]FDG-PET/CT and immune-inflammatory peripheral blood indexes in patients with advanced non-small cell lung cancer treated with first-line immune checkpoint inhibitors

Background: Inflammation in non-small cell lung cancer (NSCLC) may impair the response to immune checkpoint inhibitors (ICIs) and can be indicated by peripheral blood inflammatory indexes. 2-deoxy-2-[18 F]fluoro-D-glucose positron emission tomography/computed tomography ([18 F] FDG-PET/CT) may be used as a marker of inflammation by measuring glucose metabolism in different colonic sites. Methods: This retrospective analysis aimed to investigate the correlation between [18 F] FDGPET/CT SUVratio in six gastrointestinal districts, the spleen, the pharynx and the larynx alongside the most avid tumor lesion with peripheral blood inflammatory indexes, including the neutrophil-to-lymphocyte ratio (NLR), systemic immune-inflammatory index (SII, i.e., NLR times platelets) and lactate dehydrogenase (LDH), in patients with [18 F] FDG-PET/CT staged IV NSCLC who received first-line immune checkpoint inhibitors (ICIs). The role of SUVratios and peripheral blood inflammatory indexes in predicting overall survival (OS) and progression-free survival (PFS) was then explored. Results: A total of 43 patients were treated with first-line ICI alone (58%) or in combination with chemotherapy (42%). A significant correlation was only found between the rectosigmoid SUVratio and NLR (p = 0.0465). NLR >5.5 and LDH > 333.5 were associated with a worse OS (p = 0.033 and p = 0.009, respectively). The SII was associated with a worse PFS in patients treated with ICI alone (p = 0.033). None of the SUVratios were significantly associated with OS or PFS, although a high left colon SUVratio showed a trend toward a worse PFS. Conclusion: There was no significant correlation between [18 F]FDG PET/CT uptake in different anatomical sites, and in the tumor, and systemic immune-inflammatory indexes. The prognostic role of high left colon SUVratio deserves further investigation.