Bone scan findings of chest wall pain syndrome after stereotactic body radiation therapy: implications for the pathophysiology of the syndrome

We present a case of a 72-year-old woman treated with stereotactic body radiation therapy (SBRT) for peripherally located stage I non-small cell lung cancer (NSCLC). After treatment she developed ipsilateral grade II chest wall pain. A bone scan showed nonspecific and heterogeneous increased radiotracer uptake in the volume of ribs receiving 30% of the prescription dose of radiation (V30). We present a color wash image demonstrating excellent concordance between the V30 and the area of scintigraphic uptake on bone scan. We present a discussion of the current state of knowledge of dose volume parameters for chest wall toxicity following SBRT. This is the first case in the literature demonstrating bone scan findings corresponding to chest wall pain from SBRT. To explain these findings we propose a mechanism whereby SBRT results in bone degeneration, which prompts an increase in bone repair and an increased inflammatory state.