Rhabdomyosarcoma disease spread evaluation on CT scans: Association with primary tumor size and Ki-67 proliferation marker

Purpose: Ki-67 is a marker of cellular proliferation that is commonly used for the assessment of rhabdomyosarcoma. The aim of this study was to investigate the associations between Ki-67 expression and primary tumor diameter with CT evidence of lymph node and solid organ metastatic spread in rhabdomyosarcoma. Materials and methods: An institutional review board approval was granted for this study. A retrospective search for rhabdomyosarcoma patients was conducted. Pathology reports were examined for Ki-67 expression. Chest-abdomen CT was assessed for radiological evidence of lymph node and metastatic spread. The maximal primary tumor diameter (termed tumor size) was also measured in different modalities CT, MRI, PET-CT and US. Ki-67 levels and primary tumor maximal diameters were compared to CT evidence of lymph node and organ metastatic spread. Results: Twenty-four patients with rhabdomyosarcoma were included. CT evidence of lymph node spread was associated with Ki-67 levels (AUC = 0.896, p = 0.006) and to a lesser extent with tumor size (AUC = 0.790, p = 0.030). However, organ metastatic spread was associated only with tumor size (AUC = 0.854, p = 0.006) and not with Ki-67 levels (AUC = 0.604, p = 0.469). A combination of tumor size ≥50 mm and Ki-67 levels ≥60% was significantly associated with CT evidence of lymph node spread (p = 0.004). Conclusion: In conclusion, this study demonstrates radiological-pathological correlation in RMS. Lymph node spread detected by radiological images is associated with Ki-67 values. Lymph node and metastatic spread are associated with primary tumor size.