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

Abstract 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.