Pseudoprogression Following Liver Stereotactic Body Radiotherapy (SBRT) in a Patient With Oligometastatic Leiomyosarcoma: A Case Report

Stereotactic body radiotherapy (SBRT) is a non-invasive form of radiation that has been utilized for oligometastatic malignancies. However, pseudoprogression is a common radiological occurrence following this treatment, which manifests as an increase in tumor size before its reduction. We discuss a case of a 58-year-old female patient who initially presented with uterine leiomyosarcoma. Following surgery and postoperative radiation, she was later found to have solitary liver metastasis after three years of surveillance, which was managed by SBRT. However, on short-term follow-up, the lesion was found to have increased in size, prompting discussion regarding whether the growth was a progression of disease or a secondary effect of treatment. After close follow-up, the tumor continued to shrink until it was no longer visible on imaging. This is the first report discussing pseudoprogression following SBRT in a retroperitoneal leiomyosarcoma patient. It serves as a reminder for clinicians to consider the possibility of pseudoprogression before the failure of therapy.