SCINTIGRAPHY: Bone scintigraphy with Tc-99m MDP shows moderate focal increased uptake at the site of rib fractures. There is normal or very mild diffuse increased activity in the remainder of shoulder girdle. The exam is not significantly different from a prior bone scan 18 months earlier.
DIAGNOSIS: Osteoradionecrosis of the left shoulder girdle with lateral rib insufficiency fractures, probably with non-union. No evidence of metastatic recurrence.
Shoulder girdle radiation changes following radiation therapy for breast cancer have been reported with an incidence of 1-7 percent. The incidence is probably lower with improved delivery of treatment. Osteopenia can occur with mastectomy alone. The coarse, disorganized sclerotic appearance may superficially resemble Paget's. Insufficiency rib and clavicle fractures are common and are typically asymptomatic often with progression to incomplete union as the fragments are no longer immobilized. Radiation necrosis of the humeral head is almost always symptomatic. The latency of these changes is long, usually 2-10 years. Scintigraphic appearance with bone seeking agents should be similar to osteonecrosis from other causes, cold early on reflecting ischemia and hot during the reparative phase.
In childhood (i.e., still actively growing bone), radiation treatment can produce epiphyseal plate closure with growth retardation, bones that are hypoplastic, and scoliosis. Osteoradionecrosis, especially when severe, may be complicated by osteomyelitis. Neoplasms following radiation therapy include benign osteochrondromas which are seen exclusively in young children. Malignant transformation usually has a very long latency period, from 4-40 years, with an average of 11 years. Fifty percent are seen in a region of radiation osteitis, and include osteosarcoma, fibrosarcoma, chondrosarcoma and malignant fibrous histiocytoma.
Differentiating radiation changes from osseous metastatic recurrence can be difficult at times. MRI may be helpful in certain cases. Marrow space fibrosis presents as low signal intensity on all sequences while tumor produces high signal on T2-weighted images.
2. Dey H, Spencer R. Asymmetrical humeral head activity after therapeutic irradiation. Clin Nucl Med 1988; 13:681.
3. Datz F, Manaster B. Case report 391. Skeletal Radiology 1986; 15:566.
J. Anthony Parker, MD PhD, email@example.com