Case Report: Complete Response to Antiangiogenesis and Immune Checkpoint Blockade in an Unresectable MMR-Deficient Leiomyosarcoma Harboring Biallelic Loss of PTEN.

ABSTRACT

BACKGROUND: Leiomyosarcoma (LMS) is a malignant smooth muscle neoplasm, in which the efficacy of immune checkpoint blockade (ICB) is very limited. What is worse, loss of PTEN, known as a negative factor for ICB, frequently occurred in LMS. Seeking new strategies for LMS patients harboring loss of PTEN is important and challenging. CASE PRESENTATION A 42-year-old Chinese male was diagnosed as having unresectable LMS of the iliopsoas. After the failure of two prior chemotherapy regimens, whole-exome sequencing revealed that tumor tissue had high tumor mutation burden (689 Muts), high microsatellite instability, and some somatic mutations, including PTEN (copy number loss and p.N323fs), MSH6 (p.F1088fs), TP53 p.R273C, ASXL1 p.G645fs, ATR p.S1843P, and CDKN2A p.A118P. Then, antiangiogenic agent (pazopanib or anlotinib) plus pembrolizumab was administered from January 2 to August 6, 2018. However, pazopanib was stopped on June 18 due to the grade 2/3 adverse effect of hand-foot skin reaction, and anlotinib was administered. Considering that the tumor shrunk after immunotherapy, he underwent radical resection on September 6, 2018. The final pathological diagnosis confirmed pathologic complete response (CR). Until the latest follow-up (September 15, 2021), no progressive disease was observed and total disease-free survival has exceeded 36 months. CONCLUSION: We presented a patient with an unresectable mismatch repair (MMR)-deficient LMS harboring biallelic loss of PTEN who achieved CR from a combination strategy of antiangiogenesis plus pembrolizumab. Such a strategy might be a promising strategy to overcome the ICB resistance caused by the loss of PTEN. Such conclusions need to be further confirmed in further investigations.