Exposure to radiation therapy before age 30 increases risk. Mantle-field radiation therapy for Hodgkin lymphoma quadruples risk of breast cancer over the next 20 to 30 yr.

• 30岁前接受放疗增加危险。治疗霍杰金淋巴瘤所用的斗篷射野放疗可使其未来20-30年间的乳腺癌危险性增加4倍。