# Case Report: Primary gallbladder undifferentiated small round cell sarcomas treated with gemcitabine, paclitaxel, bevacizumab and pembrolizumab achieved remarkable tumor regression

## TL;DR

A rare gallbladder tumor showed significant shrinkage after treatment with a combination of chemotherapy, immunotherapy, and targeted drugs.

## Contribution

This is the first reported case of gallbladder USRCS treated with this specific combination therapy, showing promising results.

## Key findings

- The patient achieved partial remission lasting over 9 months with the combination therapy.
- The treatment included pembrolizumab, bevacizumab, gemcitabine, and paclitaxel.
- This case suggests that combining immunotherapy and targeted agents with chemotherapy may be effective for USRCS.

## Abstract

Undifferentiated small round cell sarcoma (USRCS) are a rare, aggressive group of tumors associated with rapid progression, metastasis, and poor prognosis. Preoperative diagnosis remains elusive, particularly for extraosseous variants, and effective treatments are lacking. This case reports the use of pembrolizumab, bevacizumab, and conventional chemotherapy (gemcitabine plus paclitaxel) as a first-line treatment for a patient with primary USRCS in the gallbladder neck; the patient achieved remarkable partial remission for more than 9 months. This case represents the second documented instance of gallbladder USRCS and the first managed with this specific combination regimen. These findings suggest that integrating immunotherapy and targeted agents with conventional chemotherapy may offer a promising therapeutic strategy for USRCS.