To analyse CA IX staining intensity as independent predictor of DFS and DSS, the following variables were entered in the multivariate (Cox) proportional hazards regression model: sex, age (young/old with median age as cutoff), treatment series (short-course RT, long-course RT and control group), preoperative tumour assessment (T), blood vessel invasion (yes/no), number of metastatic lymph nodes (LNN) (with four positive LNN as cutoff) and CA IX staining intensity. The gene discussed is CA9; the disease is neoplasm.