Immune Changes Following Trabectedin in Patients With Metastatic or Unresectable Sarcoma

PRIMARY OBJECTIVES: I. Percentage of tumor tissue in pre- and post-treatment biopsies comprised of T-cells, as determined by flow cytometry. SECONDARY OBJECTIVES: I. To explore additional potential biomarkers including: numbers of tumor associated macrophage (TAM) in tumor II. To explore additional potential biomarkers including: phenotype (classically activated macrophages \[M1\] versus \[vs\] alternatively activated macrophages \[M2\]) as characterized by CD163, CD115, CD206 on infiltrating TAM. III. To explore additional potential biomarkers including: phenotype of T cells infiltrating tumor (CD4, CD8, markers of CD4 phenotype including FoxP3 and memory). IV. To explore additional potential biomarkers including: expression T cell inhibitory markers (PD-1, CTLA-4, TIM3). V. To explore additional potential biomarkers including: recognition of autologous tumor by expanded tumor infiltrating lymphocyte lines. VI. To explore additional potential biomarkers including: in tumor infiltrating lymphocyte (TIL) expanded from myxoid/round cell liposarcomas, recognition of cancer testis antigens. OUTLINE: Patients undergo a biopsy at baseline and then receive trabectedin for up to 4 cycles. Beginning 1 week after completion of cycle 2 and prior to cycle 3, patients undergo a second biopsy. Patients who achieve clinical benefit (complete response \[CR\], partial response \[PR\], stable disease \[SD\]) after the first post-treatment scan and who continue trabectedin for 4 cycles undergo a third biopsy after cycle 4. After completion of study, patients are followed up for 30 days.