This patient had a mastectomy, axillary clearance and local radiotherapy many years ago for breast carcinoma. There has been no recurrence of the carcinoma. There are marked changes in the bones in the radiation field, including ribs, clavicle, and scapula (click on image for a magnified view). The humerus has been removed. There is evidence of right upper lobe fibrosis, with elevation of the right hilum. There is right apical pleural thickening.
Radiation osteonecrosis occurs due to vascular compromise with obliterative endarteritis, and damage to osteoblasts and osteoclasts. The dose required is greater than 6 Gy in adults, and onset is >1 year after radiotherapy. Findings include focal lucency, periostitis, sclerosis, insufficiency fracture, and cortical thinning. Bone scan shows decreased uptake in the radiation field. There is an increased susceptibility of irradiated bone to infection, which may contribute to the changes seen. There is an increased risk of developing bone sarcomas in the irradiated field (latency > 5 years).
Reference: Dahnert W. Radiology Review Manual 5th edition. Lippincott, Williams & Wilkins 2003
Credit: Dr Laughlin Dawes