Late toxic effects of radiation
Late toxic effects of radiation therapy, though uncommon, can include radiation pneumonitis, cardiac events, arm edema, brachial plexopathy, and the risk of second malignancies. Such toxic effects can be minimized with current radiation delivery techniques and with careful delineation of the target volume.
In a retrospective analysis of 1,624 women treated with conservative surgery and adjuvant breast radiation at a single institution, the overall incidence of symptomatic radiation pneumonitis was 1.0% at a median follow-up of 77 months. The incidence of pneumonitis increased to 3.0% with the use of a supraclavicular radiation field and to 8.8% when concurrent chemotherapy was administered. The incidence was only 1.3% in patients who received sequential chemotherapy.[Level of evidence: 3iii]
Controversy existed as to whether adjuvant radiation therapy to the left chest wall or breast, with or without inclusion of the regional lymphatics, had an association with increased cardiac mortality. In women treated with radiation therapy before 1980, an increased cardiac death rate was noted after 10 to 15 years, compared with women with nonradiated or right-side-only radiated breast cancer.[62,68,69,70] This was probably caused by the radiation received by the left myocardium.
Modern radiation therapy techniques introduced in the 1990s minimized deep radiation to the underlying myocardium when left-sided chest wall or left-breast radiation was used. Cardiac mortality decreased accordingly.[71,72] At this time, cardiac mortality was also decreasing in the United States.
An analysis of SEER data from 1973 to 1989 reviewing deaths caused by ischemic heart disease in women who received breast or chest wall radiation showed that since 1980, no increased death rate resulting from ischemic heart disease in women who received left chest wall or breast radiation was found.[73,74][Level of evidence: 3iB]
Lymphedema consequent to cancer management remains a major quality-of-life concern for breast cancer patients. Single-modality treatment of the axilla (surgery or radiation) is associated with a low incidence of arm edema. Axillary radiation therapy can increase the risk of arm edema in patients who received axillary dissection from 2% to 10% with dissection alone to 13% to 18% with adjuvant radiation therapy.[75,76,77] (Refer to the PDQ summary on Lymphedema for more information.)
Radiation injury to the brachial plexus following adjuvant nodal radiation therapy is a rare clinical entity for breast cancer patients. In a single-institution study using current radiation techniques, 449 breast cancer patients treated with postoperative radiation therapy to the breast and regional lymphatics were followed for 5.5 years to assess the rate of brachial plexus injury. The diagnosis of such injury was made clinically with computerized tomography to distinguish radiation injury from tumor recurrence. When 54 Gy in 30 fractions was delivered to the regional nodes, the incidence of symptomatic brachial plexus injury was 1.0% compared with 5.9% when increased fraction sizes (45 Gy in 15 fractions) were used.