Objective: To determine the prognostic biomarker capability of neo-adjuvant mid-therapy FDG PET for sarcoma monitoring.

Methods: Patients with a sampling of sarcoma subtypes presenting to clinic and treated with neo-adjuvant chemotherapy according to standard clinical practice had baseline, mid-therapy (after 2 cycles of chemotherapy) and pre-resection FDG PET studies. Tumor FDG SUV maximum at each timepoint, tumor type, location, size, gender, and histopathologic grade along with patient age were recorded. Months from baseline FDG PET to events of tumor local recurrence, metastasis, or death were determined from clinical records for comparison with imaging data. Baseline tumor uptake data, with the addition of the variable for percent difference between the baseline and mid-therapy FDG tumor maximum to describe change mid-therapy were analyzed for association with outcome in a model that included all other available covariates. Data was analyzed using univariate and multivariate Cox regression analyses to evaluate the contribution of the PET FDG response for predicting death, metastases, or tumor local recurrence.

Results: Data from 65 patient studies were analyzed. Univariate and multivariate analyses showed that the difference in FDG PET tumor maximum uptake added significantly to the prognostic ability of the model using baseline tumor uptake alone with the other clinical covariates. The median value for this difference for the group was 35.7% with a difference below that value implying a significantly higher risk for poor outcome. Additionally, Cox regression analysis showed that there is a continuous dose effect for FDG PET tumor uptake values and FDG PET percent change. Local recurrence was predicted independently from metastases.

Conclusion: Mid-neo-adjuvant therapy FDG PET tumor uptake in sarcoma patients can be used as an imaging biomarker for prediction of local recurrence, metastases, and overall survival.

Supported by NIH/NCI CA 65537 and SFI 11/PI/1027

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B146.

Citation Format: Janet F. Eary, Janet O'Sullivan, Finbarr O'Sullivan, Ernest U. Conrad. Mid-therapy FDG PET as an outcome biomarker in sarcoma patients. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B146.