Radiation Fibrosis After Stereotactic Body Radiation Therapy for Osseous Metastases: A Case Report

Abstract

Radiation-induced fibrosis is a potentially severe late complication after high-dose radiotherapy. Over the last decade, there has been increasing use of stereotactic body radiation therapy (SBRT) to treat both primary and metastatic malignancies. While there has been evolving evidence of appropriate dose constraints for certain organs receiving hypofractionated radiotherapy, the risk, and appropriate dose constraints to limit the risk of radiation-induced muscle fibrosis are poorly defined. In this report, two patients are presented who underwent SBRT for osseous oligometastatic renal cell carcinoma. While the treatment was well-tolerated with no acute toxicities and complete local control of the metastasis, both patients experienced late toxicity of radiation-induced fibrosis in the adjacent musculature. In both cases, toxicity was nonresponsive to medical interventions and was severe enough to require surgical resection of the affected tissue. Following surgery, both patients reported improved pain relief and mobility. Further studies are needed to explore the dose constraints that may reduce the risk of radiation-induced muscle fibrosis in five-fraction treatment.

Keywords: myositis; oligometastatic; radiation-induced fibrosis; renal cell carcinoma; stereotactic body radiation therapy.

Figure 1. Post-treatment MRI

Post-treatment T2 axial MRI showing evidence of edema and enhancement in previously treated region

Figure 2. Stereotactic Body Radiation Therapy (SBRT) Treatment Plans

Outlined are images of isodose color wash for each patient’s body site (scapula (A), Iliac (B)). Muscle contour is outlined in black. Prescription dose (40Gy) is outlined in yellow.