Only the research by de Heer et al. has found a significant association (p = 0.06) between the COX-2 expression and grading; a poor grade of differentiation was associated with high COX-2 expression levels in pretreatment specimens; a high level of COX-2 expression was more often observed both in irradiated and non-irradiated adenocarcinomas [75]. The gene discussed is PTGS2; the disease is adenocarcinoma.