The Importance of incomplete Repair in Hyperfractionated Radiotherapy Lai-Lei Ting Department of Radiation Oncology National Taiwan University Hospital Theoretically, hyperfractionated radiotherapy can greatly spare late-responding tissues. However, the interval time which allows sublethal damage to be repaired is critical. The repair half-life is longer for lateresponding tissues as comparison with that of early-responding tissues. Besides, the larger the dose, the repair time would much prolong. In 1985, Thames proposed incomplete-repair model which insinuated that even the fraction size is very small, the total dose could not be highly escalated. By experiments and clinical trials, the best interval time is at least 6 to 8 hours. Otherwise, since there is incomplete-repair existed, the late complications will be grim.