Testicular tumour most sensitive to radiation is
Teratoma
Lymphoma
Mixed germ cell tumour
Seminoma
Seminomas are most radiosensitive. So after orchidectomy radiotherapy is given to increase the cure rate and also to reduce relapse(excellent results in stage 1 and 2 seminomas). Radiotherapy is not beneficial in teratomas as they are less radiosensitive. Other radiosensitive tumours are squamoua cell carcinoma, basal cell carcinoma, hodgkin's lymphoma.Reference : page 1087 and1143 SRB's manual of surgery 5th edition
Urology