A groundbreaking case study reveals a promising development in cancer treatment. Researchers have discovered that a patient with a rare form of dedifferentiated liposarcoma (DDLPS) and a high tumor mutational burden (TMB) achieved a remarkable response to pembrolizumab, an immune checkpoint inhibitor (ICI). This patient's story highlights the potential of ICIs in treating DDLPS, a condition often associated with a poor prognosis and limited treatment options. The patient's high TMB and high tumor-associated macrophages (TAM) density in the tumor microenvironment (TME) may have played a crucial role in their positive response to the treatment. This case report, published in the World Journal of Surgical Oncology, is the first to document a pathological complete response (pCR) to pembrolizumab in a patient with recurrent retroperitoneal DDLPS. The patient's initial diagnosis of prostate cancer with lung and bone metastases and subsequent discovery of a retroperitoneal tumor further complicated their condition. Despite initial treatment with doxorubicin, pazopanib, and eribulin, the disseminated lesions continued to grow. However, genomic profiling revealed a high TMB, leading to the prescription of pembrolizumab. The therapy achieved a partial response, significantly reducing target lesions. Unfortunately, the patient experienced grade 3 ICI-induced inflammatory arthritis, leading to the discontinuation of pembrolizumab. A second radical surgery followed, resulting in the removal of 9 disseminated lesions and a pCR with extensive hyalinization and necrosis, free of residual viable tumor cells. Remarkably, the patient survived disease-free 15 months after the second surgery. This case study emphasizes the importance of further research to identify predictive biomarkers for ICIs in DDLPS, as it suggests a potential correlation between high TMB and ICI response. The authors also highlight the need to refine predictive biomarkers for ICIs in this malignancy, as current evidence is limited and may be influenced by the use of doxorubicin in priming the TME for ICI therapy.
