The clinical utility of circulating tumor cells (CTCs) has been investigated in numerous publications, but CTCs that express very typical immune cell markers have not been reported. Here we report a novel class of CTCs-CSV-positive macrophage-like CTCs (ML-CTCs). This nomenclature was based on the fact that this class of CTCs can be captured from blood samples of gastrointestinal stromal tumors (GISTs) patients using either the macrophage marker CD68 or our proprietary tumor-specific cell-surface vimentin (CSV) antibody 84-1; likewise, the captured ML-CTCs can be co-stained with both typical macrophage markers (CD14, CD68) and tumor cell markers (DOG-1, C-kit) but not CD45. Patients with metastatic GIST had significantly greater numbers of ML-CTCs than patients with localized GIST or cancer-free blood donors (P<0.0001). Unexpectedly, the classic CSV positive CTCs was abundant in metastatic disease but failed to predict GIST metastasis. Only CSV-positive ML-CTCs was able to serve as a solid and novel biomarker for prediction of metastatic risk in GIST patients.

Background Avapritinib, a novel inhibitor of KIT/PDGFRA, is approved in the U.S. for the treatment of adults with PDGFRA exon 18‐mutant unresectable or metastatic gastrointestinal stromal tumors (U/M GISTs). We assessed the safety of avapritinib and provide evidence‐based guidance on management of avapritinib‐associated adverse events (AEs), including cognitive effects and intracranial bleeding. Materials and Methods We performed a post hoc analysis of data from a two‐part, single‐arm dose escalation/expansion phase I study (NAVIGATOR; NCT02508532) in patients with U/M GISTs treated with oral avapritinib 30–600 mg once daily. The primary endpoints were safety and tolerability; the impact of dose modification (interruption and/or reduction) on progression‐free survival (PFS) was a secondary endpoint. Efficacy analyses were limited to patients who started avapritinib at 300 mg (approved dose). Results Of 250 patients enrolled in the study, 74.0% presented with KIT mutation and 24.8% presented with PDGFRA exon 18‐mutation; 66.8% started avapritinib at 300 mg. The most common treatment‐related AEs (any grade) were nausea (59.2%), fatigue (50.0%), periorbital edema (42.0%), anemia (39.2%), diarrhea (36.0%), vomiting (36.0%), and increased lacrimation (30.8%). No treatment‐related deaths occurred. Among 167 patients starting on 300 mg avapritinib, all‐cause cognitive effects rate (grade 1–2) was 37.0% in all patients and 52.0% in patients ≥65 years. Cognitive effects improved to a lower grade more quickly with dose modification (1.3–3.1 weeks) than without (4.9–7.6 weeks). Median PFS was 11.4 months with dose modification and 7.2 months without. Conclusion Tolerability‐guided dose modification of avapritinib is an effective strategy for managing AEs in patients with GISTs. Implications for Practice Early recognition of adverse events and tailored dose modification appear to be effective approaches for managing treatment‐related adverse events and maintaining patients on avapritinib. Dose reduction does not appear to result in reduced efficacy. Patients' cognitive function should be assessed at baseline and monitored carefully throughout treatment with avapritinib for the onset of cognitive adverse events. Dose interruption is recommended at the first sign of any cognitive effect, including grade 1 events.

Background: Gastrointestinal stromal tumors (GISTs) are the most common gastrointestinal tract sarcomas and are heavily infiltrated with tumor-associated macrophages (TAMs). Biomarkers specifically capturing circulating tumor cells (CTCs) that can be used to noninvasively determine the disease status in GIST patients have been lacking. Patients and Methods: To fill this gap, we captured both regular CTCs and TAMs from GIST patients' blood and tumor samples using our proprietary cell-surface vimentin (CSV) antibody 84-1 and the TAM markers CD14 and CD68 based on our previous established CTC detection method from 104 localized or metastatic sarcoma patients and 10 healthy donors. Also, freshly procured metastatic GIST tissues were obtained from four patients. Results: We defined a rare population of CSV+ macrophage-like CTCs (ML-CTCs) in metastatic GIST patients' blood samples with expression of CD14 and CD68 but not CD45. Also, we demonstrated CSV+ ML-CTCs to be tumor microenvironment-derived. Metastatic GIST patients had markedly higher numbers of CSV+ ML-CTCs than localized GIST patients and healthy blood donors. However, regular CTC counts could not predict metastasis of GISTs but could for other types of sarcoma. Notably, CSV+ ML-CTCs were represented as M1-like macrophages in their phenotype and function. Conclusions: CSV+ ML-CTCs are novel biomarkers for prediction of metastatic risk and therapeutic response in GIST patients. Routinely monitoring these cells will be an important approach to liquid biopsy analysis of GISTs. Citation Format: Heming Li, Qing H. Meng, Hyangsoon Noh, Neeta Somaiah, Keila E. Torres, Xueqing Xia, Izhar Singh Batth, Cissimol P. Joseph, Zachary A. Mulder, Ruoyu Wang, Shulin Li. Cell-surface vimentin-positive macrophages like CTCs as novel biomarkers of metastatic gastrointestinal stromal tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1107.

During JADPRO Live Virtual 2020, Cissimol Joseph, APRN, AOCNP®, and Prachee Singh, PA-C, MS, highlighted the clinical features and diagnostic workup of soft-tissue sarcoma and presented on a multidisciplinary approach to treatment planning.

TSC-mutated sarcomas are rare molecular and histologic types of sarcoma. Due to the presence of their specific oncogenic driver mutation, these sarcomas are particularly sensitive to mTOR inhibitors. Recently, nab-sirolimus, an albumin-bound mTOR inhibitor, was approved by the Food and Drug Administration (FDA) for PEComas, which harbor a TSC mutation, and this drug remains the only FDA-approved systemic treatment for these tumors. We report on two cases of patients with TSC-mutated sarcomas who experienced significant responses to the combination of gemcitabine and sirolimus, after progression on prior gemcitabine-based chemotherapy and single agent mTOR inhibition with nab-sirolimus. Preclinical and clinical data support rationale for a synergistic effect of the combination. This combination may represent a valid therapeutic option after failure of nab-sirolimus in these patients, with no standard-of-care treatment options.