Imaging changes following stereotactic radiosurgery for metastatic intracranial tumors: differentiating pseudoprogression from tumor progression and its effect on clinical practice

Abstract

Stereotactic radiosurgery has become standard adjuvant treatment for patients with metastatic intracranial lesions. There has been a growing appreciation for benign imaging changes following radiation that are difficult to distinguish from true tumor progression. These imaging changes, termed pseudoprogression, carry significant implications for patient management. In this review, we discuss the current understanding of pseudoprogression in metastatic brain lesions, research to differentiate pseudoprogression from true progression, and clinical implications of pseudoprogression on treatment decisions.

Fig. 1

Suspected progression actually due to pseudoprogression. A 64-year-old female presented with multiple intracranial metastases secondary to primary breast cancer. Her initial diagnosis of breast cancer was made in 2005 and confirmed to be ER+/PR−. In 2010, she developed multiple intracranial metastases and was subsequently treated with WBRT. One year later, multiple new intracranial metastases were found, including a one lesion in the left parietal lobe. b The patient was treated with SRS at a dose of 1,600 cGy to the 80 % isodose line. c Follow-up MRI at 4 months and at d 7 months post-SRS showed an increase in lesion size consistent with tumor progression. Due to the onset of neurologic symptoms, the patient underwent a craniotomy for suspected tumor progression. However, intraoperative and final pathology confirmed radiation necrosis without evidence of any viable tumor