RRM2B and neoplasm: When the correlation of p53, p53R2, and p21 expression with histological effect was analysed, CRT was effective in p53 (−) tumours (P=0.041) or p53R2 (−) tumours (P=0.0018), whereas p21 expression did not influence histological effect (P=0.68, data not shown) (Table 3).