Figure 1. Actual incidence of chronic nephropathy as a function of renal dose. Chronic nephropathy was defined as increased serum creatinine, increased blood urea nitrogen and decreased glomerular filtration rate accompanied by anaemia and hypertension, and without any obvious cause other than radiation [18]. The number of patients at risk are shown in parentheses, and the plots stop when there were fewer than six patients still at risk. Actuarial log rank analysis was done to compare the incidence of chronic nephropathy by renal dose. Trend analysis was done using the Cox proportional hazards model, and a statistically significant trend (p=0.012) exists for decreasing renal dose and decreasing incidence of chronic nephropathy. Adapted with permission from Lawton et al [18].