Identifying and quantifying tumor burden by in-vivo labeling and surgical specimen PET/CT imaging

Objectives In an ongoing prospective clinical trial, we were able to assess the ability of PET/CT to identify and quantify tumor burden within surgical specimens. This methodology exploits the avidity of PET radiotracers for malignant cells in order to more accurately stage and treat patients with a wide variety of cancers.

Methods Sixteen patients with a variety of cancers participated in this study. Each patient received a dose of FDG on the day of surgery. Immediately following resection, the surgical specimen was imaged with a PET/CT. The specimen was then cut in a grid-like fashion to yield 1X1X0.5cm pieces. These pieces were imaged, weighed, and activity quantified in a well counter. The pieces were then sent to pathology for correlation.

Results 105 pieces of tissue were microscopically analyzed and correlated with maximum voxel activity (MVox) based on PET/CT and quantification of activity from the well counter (WellCounts). Significant differences were found in the MVox and WellCounts of pieces containing tumor compared to pieces free of tumor on microscopic examination (P< 0.001). We also found a correlation between both MVox and WellCounts compared to tumor burden within each piece of tissue.

Conclusions This methodology allows for identification and quantification of tumor burden within surgical specimens. This information can be used intraoperatively to assess surgical margins, as well as help guide pathology sampling of surgical oncology specimens. Ultimately, this has potential to improve patient outcomes.