Abstract
Radiotherapy with conventional deep x-ray beams has been used to treat a
number of cancers, such as breast, endometrial, and cervical carcinoma (49-52).
The development of sarcoma, melanoma, SCC, and BCC within the radiation field
many years after the treatment of the first cancer is a recognized but rare complication (49-52). Less common is the development of ulcerated second cancers within the
irradiated fields. It is believed that radiation causes irreversible DNA damage, leading to gene mutations and deletions (49). On a molecular level, the proto-oncogene
c-jun and the inactivation of tumor suppressor genes p53 and rb occur. A cancer is
classified as radiation induced if: (1) the cancer is present within the previously irradiated field (typically this occurs 3-5 years after the initial treatment in which at least
25-80Gy of radiation were delivered), and (2) the two cancers (the previously treated
and the new cancer) must be histologically different (49). Squamous cell carcinoma
and basal cell carcinoma are the most common radiation-induced carcinomas (51).
Angiosarcomas are the rarest, with a risk of 0.04%. When angiosarcomas do occur,
they usually present after radiation therapy to the breast (50). Surgical excision is
the preferred treatment; however, chemotherapy and reirradiation may have some
therapeutic benefit (49).