Elevated p21 expression is associated with poor prognosis of rectal stromal tumors after resection

Background and Objectives: The pathogenic role of alteration of cell-cycle proteins in rectal stromal tumors (GISTs) remains unclear. This study aimed to elucidate the prognostic role of p21 to compare with p53, PCNA, and Ki-67 in rectal GISTs. Methods: Forty-nine surgically resected CD 117 (+) rectal GISTs were enrolled from 1986 to 2006. Immunohistochemical studies were performed with antibodies of p21, p53, PCNA, and Ki-67. Results: The labeling index (LI) of immunoreactivities range from 0% to 65% for p53, 0% to 60% for p21, 0% to 67% for Ki-67, and 30% to 93% for PCNA. LI of four markers were positively correlated (P < 0.05). LI of four markers were also positively correlated with tumor mitosis and tumor size (P<0.05). Tumors with high p53, p21, or Ki-67 LI were associated with increased NIH risk, non-spindle cell type, and high cell pleomorphism (P < 0.05). Survival analyses demonstrated that large tumor size (P = 0.012), high tumor mitosis (P < 0.001), increased NIH risk (P = 0.003), high cell pleomorphism (P = 0.004), high p53 LI (P = 0.005), high p21 LI (P = 0.009), high PCNA LI (P = 0.001), and high Ki-67 LI (P = 0.042) were poor prognostic factors for disease-specific survival. Conclusions: Elevated p21 expression is associated with poor prognosis of rectal stromal tumors after resection.