Pre-treatment proliferation and the outcome of conventional and accelerated radiotherapy

This study investigated the influence of pre-treatment proliferation characteristics, assessed by Ki-67 staining, in patients treated in the CHART trial of accelerated radiotherapy in head and neck cancer. Histological material from 402 patients was collected and stained for the presence and pattern of Ki-67 staining. Locoregional control and overall survival were the main clinical endpoints. Increasing Ki-67 positivity was associated with decreasing differentiation (P<0.001) and increasing N-stage (P<0.004). Increasing N-stage was also associated with the progression of proliferation pattern from marginal to random (P<0.001). Using a multivariate model, a trend was seen towards a greater benefit from CHART in the lower Ki-67 tumours (P=0.08); this became significant by pooling the low and intermediate Ki-67 groups in comparison with the high Ki-67 group (P=0.032). Tumours with marginal proliferation pattern showed a lower hazard ratio with CHART versus conventional for locoregional control (P=0.005). The data presented in this study do not support that a high pre-treatment Ki-67 is associated with a therapeutic benefit from accelerated radiotherapy.