Next generation sequencing predicting clinical effect of immunotherapy on adult rhabdomyosarcoma patient: A case report.

Rationale: Rhabdomyosarcoma (RMS) is a rare sarcoma that rarely occurs in adults and accounts for only 1% of all adult tumors. The standard treatment for RMS is surgical resection, radiotherapy, and chemotherapy.

Patient Concerns: Adult patients often present with an aggressive course and poor prognosis.

Diagnoses: The patient was diagnosed with RMS in September 2019 and was confirmed by hematoxylin-eosin staining and immunohistochemistry after surgical resection.

Interventions: The patient received surgical resection in September 2019. He was admitted to another hospital after the first recurrence in November 2019. After the second routine surgical resection, the patient underwent chemotherapy, radiotherapy, and anlotinib maintenance treatment. He relapsed again in October 2020 and was admitted to our hospital. Next-generation sequencing was performed on the punctured tissue of the patient's lung metastatic lesion, and high tumor mutational burden (TMB-H), high microsatellite instability (MSI-H), and positive programmed death-ligand 1 (PD-L1) were observed. The patient then received toripalimab and anlotinib combined therapy and was evaluated for a partial response after 2 months.

Outcomes: This benefit has persisted for more than 17 months.

Lessons: This is the longest progression-free survival for PD-1 inhibitors in RMS, and there is a trend of continued extension of progression-free survival in this patient. This case supports the hypothesis that positive PD-L1, TMB-H, and MSI-H could be beneficial biomarkers for immunotherapy in adult RMS.