The following is the summary of “Role of Preoperative Imaging in the Detection of Lateral Lymph Node Metastases in Rectal Cancer: A Systematic Review and Diagnostic Test Meta-analysis” published in December 2022 issue of Diseases of the Colon & Rectum by Rooney, et al.

Lateral lymph nodes in rectal cancer can be imaged using various methods. The purpose of this research was to evaluate the efficacy of 18F-FDG-PET/CT, 18F-FDG-PET/MRI, and pelvic MRI in detecting lateral lymph node metastases in rectal cancer. PubMed, Embase, the Cochrane Library, and Google Scholar are all good places to look for information. For the purpose of preoperative detection of lateral lymph node metastases in patients with rectal cancer, all studies comparing the diagnostic accuracy of pelvic Magnetic resonance imaging(MRI), 18F-FDG-PET/CT, and 18F-FDG-PET/MRI were chosen.

Interventions included a pelvic MRI, a combination of a PET/CT scan and an MRI scan using fluorodeoxyglucose (18F-FDG-PET/CT), and a Polyethylene terephthalate(PET) scan. Researchers employed a gold standard of definitive histopathology to evaluate the results. In the end, out of the 7,360 studies in the original search, only 20 were included (including 1,827 patients). For the detection of lateral lymph node metastases, the pooled sensitivity of pelvic MRI was 0.88 (95% CI, 0.85-0.91), of 18F-FDG-PET/CT was 0.83 (95% CI, 0.80-0.86), and of 18F-FDG-PET/MRI was 0.72 (95% CI, 0.51-0.87). The combined specificity of 18F-FDG-PET/CT was 0.95 (95% CI, 0.86-0.98), that of 18F-FDG-PET/MRI was 0.90 (95% CI, 0.78-0.96), and that of pelvic MRI was 0.85 (95% CI, 0.78-0.90). When comparing pelvic MRI and 18F-FDG-PET/CT, the area under the curve for the former was 0.88 (95% CI, 0.85-0.91), while the latter was 0.83 (95% CI, 0.80-0.86).

The heterogeneity of patient demographics, definitions of questionable lateral lymph nodes, and the administration of neoadjuvant treatment all provide challenges. Nevertheless, the findings of this review suggest that pelvic MRI is the imaging modality of choice for preoperative detection of lateral lymph node metastases in rectal cancer. In contrast, the higher specificity of 18F-FDG-PET/MRI allows the elimination of false positive instances when confirming the presence of lateral lymph node metastases.