[Therapy-induced effects in normal tissue]

More than 50% of cancer patients survive for more than 5 years, owing to modern and effective treatment. Therefore, long-term sequelae of treatment are more frequently seen than in the past. Such effects on normal tissue may both mimic and obscure tumor recurrences. Besides the direct consequences of surgery, tissue damage due to radiation or chemotherapy frequently cause problems in differential diagnosis. Among the numerous sequelae of radiotherapy, the most prominent are disturbance of the blood-brain barrier, radiation pneumonitis, osteodystrophy and osteoradionecrosis, fatty changes of bone marrow, or increased radiodensity of breast parenchyma. Chemotherapy may cause, e.g., diffuse abnormalities of white matter, pneumonitis and lung fibrosis, cardiomyopathy, or diffuse and patchy changes in bone marrow signals in MRI. The most devastating long-term complications are secondary cancers and leukemia induced by both radiotherapy and chemotherapy.