Total Lesion Glycolysis As A Predictor Of Pathologic Outcomes Locally Advanced And Borderline Resectable Patients Undergoing Surgery After Preoperative Stereotactic Body Radiation Therapy

For patients with locally advanced (LA) or borderline resectable (BR) pancreatic cancer, stereotactic radiation body therapy (SBRT) has resulted in a fraction of patients undergoing margin negative surgery with pathologic complete response. In patients with LA/BR disease, it would be helpful to more reliably identify those patients with a greater likelihood of having a favorable outcome at surgery. Positron emission tomography (PET) imaging metrics, including total lesion glycolysis, has shown utility in predicting local control for locally advanced patients undergoing SBRT. Whether PET can also predict for eventual margin negative resection and pathologic complete response in LA/BR patients proceeding to surgery is uncertain. Thirty patients from our institution with LA/BR pancreatic cancer treated with baseline PET imaging who were treated with upfront chemotherapy followed by hypofractionated SBRT and attempted surgery were identified. Total lesion glycolysis (TLG) was calculated using in-house software. Disease was measured at a threshold based on the liver SUV using the equation Livermean+(2*Liversd). TLG was defined as the volume of tumor tissue that demonstrated metabolic activity at or above the calculated threshold of disease measurability multiplied by the mean SUV within the volume. Endpoints included near/complete pathologic response and margin negative resection. The prognostic utility of TLG for predicting each endpoint was assessed using a multivariate logistic regression model, controlling for age, stage, type of chemotherapy, and radiation dose. Median was 59.7 years, with 47% being male. LA disease was present in 77% of patients, with the remaining 23% having BR disease. All patients received initial chemotherapy, including 63% who received FOLFIRINOX and 37% who received gemcitabine-based chemotherapy. Majority (80%) of patients were treated with an SBRT to 33 Gy (range 25-33 Gy). Pathologic near/complete response and margin negative resection were present in 37% and 83% of patients, respectively. The percentage of patients undergoing pre-chemotherapy, pre-SBRT, and post-SBRT PET imaging were 27%, 77%, and 37%, respectively. On multivariate logistic regression, TLG>50 was associated with increased odds of experiencing near/complete pathologic response (OR: 2.59, p=0.049), but was not significantly associated with margin negative resection. In patients undergoing SBRT for locally advanced/borderline resectable disease, TLG on PET scan may identify those patients at increased likelihood of having favorable pathologic outcomes at surgery. Further validation of this concept should be pursued.