Clinical feasibility of 68Ga-DOTATATE PET/CT to identify SSTR-positive soft tissue sarcoma for PRRT selection.

Abstract

TPS11590 Background: Soft tissue sarcomas (STS) are biologically heterogeneous with limited effective systemic options in advanced disease. While 18F-FDG PET/CT provides metabolic assessment, it does not identify actionable receptor targets. Somatostatin receptor 2 (SSTR2) is expressed in subsets of mesenchymal tumors, and SSTR-targeted imaging with 68Ga-DOTATATE PET/CT is routinely used to select patients with neuroendocrine tumors for peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE. Whether receptor-targeted PET screening can feasibly characterize SSTR expression across STS subtypes and support future PRRT trial design is unknown. This study evaluates the feasibility and yield of 68Ga-DOTATATE PET/CT as a screening strategy in STS. Methods: This is a prospective, open-label, single-center pilot study enrolling 30 adults with any-stage STS who are candidates for systemic therapy and who have undergone standard-of-care PET/CT within 30 days. Participants undergo a single 68Ga-DOTATATE digital PET/CT within 14 days of consent, acquired approximately 60 minutes post-injection with non-contrast CT for attenuation correction and anatomic localization. Quantitative metrics including SUVmax and total tumor volume are centrally derived. Optional biobanking permits pre-imaging blood collection for exploratory circulating biomarkers. Key exclusions include recent long-acting somatostatin analog use, pregnancy or lactation, acute infection, hypersensitivity to somatostatin analogs, or inability to complete imaging. The primary endpoint is screening feasibility, defined by successful scan acquisition and interpretable image quality. Secondary endpoints include lesion-level detectability, safety, and characterization of uptake patterns using modified Krenning-style criteria and quantitative PET parameters across histologic subtypes. Imaging findings may be reviewed at multidisciplinary sarcoma tumor board as part of routine clinical care, including discussion of potential PRRT eligibility, but tumor board recommendations are not study endpoints. Exploratory analyses will assess concordance between imaging findings and available tumor immunohistochemistry or circulating biomarkers. Analyses are descriptive. The planned accrual is 30 patients over approximately 24 months at a high-volume sarcoma center. Enrollment and imaging are ongoing. This study will establish the feasibility of receptor-targeted PET screening in STS and characterize the frequency and distribution of SSTR-positive disease, providing data necessary to inform the feasibility and design of subsequent 177Lu-DOTATATE interventional trials. Clinical trial information: NCT06500065 .