<prompt> What is the principle behind radiotherapy in malignancy?Ionisation of DNADehydration of DNACharring the nucleusUltrasonic effect  <response>: Radiotherapy is the treatment of cancer with ionizing radiation. It works by damaging the DNA within the tumor cells, making them unable to divide and grow. The goal of radiation therapy is to maximize the dose to tumor cells while minimizing exposure to normal, healthy cells. Ref: Emami B et al. 1991 