Areas that have been irradiated should be regularly observed not only for recurrence of the initial tumor or its metastasis, and for late radiation effect, but also for the possibility of development of a New Cancer. Additional or returning symptoms may indicate recurrence OR metastasis of original tumor, OR radiation damage, OR a New Primary Cancer developing at that site. Differentiation of radiation pathology from recurrent or metastatic tumor or new malignancy can be difficult. 
Because the target organ for the development of late effects is most probably the endothelial cells lining the blood vessels, much of the permanent damage is caused by impairment of circulation, as these blood vessels undergo premature and progressive aging, scarring, and arteriosclerosis. Hyperbaric oxygen should be considered when managing late-onset sequelae in previously irradiated patients. The use of hyperbaric oxygen for radiation-induced bone and soft tissue complications is safe and results in few significant adverse effects. 
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Subsequent surgery--Irradiation for malignancy in an area makes subsequent surgery more difficult. Injection of intravenous contrast medium [and subsequent Xrays] might help identify the vascular structures within the area, especially when disease process and post-irradiation fibrosis have destroyed the tissue planes.  Because of the damage to blood vessels, there may be poor healing in previously irradiated areas.  Hyperbaric oxygen therapy can help irradiated tissues heal faster. 
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One study followed 221 consecutively treated patients for 8 to 42 years after post mastectomy irradiation. Complications requiring in-hospital treatment were observed in 24 of 221 patients (11%). There were four sarcomas of the treated chest wall, three squamous carcinomas (two in the esophagus), two angiosarcomas of the swollen homolateral arm, nine chronic ulcers, five respiratory insufficiencies, six pathologic fractures of the radiated shoulder or ribs, two fatal cardiomyopathies, one persisting leukopenia with fatal brain abscess, and one severe neurovascular impairment of the arm. In a comparable group of 394 consecutive post mastectomy patients who were not irradiated, one similar event, a myxosarcoma of an unswollen arm, was observed. Only long-term follow-up can determine the ultimate risks of radiotherapy. 
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Spiral CT scans of abdomen, pelvis and chest, with or without contrast, every three months, has its own radiation risk as well. Admittedly, it is smaller than irradiation for eradication of malignancy. The radiation burden from diagnostic CT scans may ultimately contribute to carcinogenesis, mutagenesis and other radiation damage. 
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Radionecrosis is the death of tissue in small patches, in the areas of irradiation.  If it occurs in bone, the structural strength of the bone is much decreased.  If it occurs in the brain, it can lead to dementia and death.

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