Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
2107 - Investigation of the Subcutaneous-to-Visceral Fat Ratio as a Prognostic Biomarker for Survival after Ablative MR-Guided Adaptive Radiotherapy for Pancreatic Cancer
Presenter(s)
Naseem Ud Din, PhD - Miami Cancer Institute: Baptist Health South Florida, Miami, FL
A. Kaiser1, N. Ud Din1, K. Sehrawat2, L. Hodgson3, R. Herrera4, M. D. Hall5, Y. Weiss4, R. Kotecha6, A. Gutierrez1, M. P. Mehta7, M. D. Chuong1, and K. E. Mittauer4; 1Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 2Baptist Health South Florida, Miami, FL, 3Department of Biostatistics, Miami Cancer Institute, Miami, FL, 4Department of Oncological Sciences, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 5Miami Cancer Institute, Miami, FL, 6Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 7Department of Radiation Oncology, Miami Cancer Institute, Miami, FL
Purpose/Objective(s):
Low visceral fat density is associated with an overall survival (OS) benefit for patients with advanced pancreatic ductal adenocarcinoma (PDAC) receiving chemotherapy. We hypothesized that a similar relationship may exist post radiotherapy (RT) in borderline and locally advanced disease. Here, we examined the prognostic impact of the subcutaneous fat (SF) to visceral fat (VF) ratio (SVR) in PDAC patients receiving stereotactic MR-guided adaptive radiation therapy (SMART).
Materials/Methods:
Patients with borderline resectable or locally advanced PDAC who received SMART between 2018 and 2024 were analyzed. SVR was calculated by quantifying VF and SF volumes (cc) on a 0.35 T TRUFI MR simulation scan at a single plane at the L2 vertebral body level using a semi-automated segmentation workflow. VF and SF contours were reviewed and edited by a radiation oncologist. SVR was then compared to patient characteristics and outcomes. Progression free survival (PFS) and OS were estimated from diagnosis with the Kaplan-Meier method. Cox proportional hazards regression model was used for group comparisons.
Results:
105 patients were evaluated with a median follow-up of 33 months. Median age was 69 years. The majority were male (56%) with T4 primaries (72%) and were node negative (74%). Median largest tumor dimension was 3.7cm (range, 1.5-9 cm) with pre-SMART median CA19-9 of 43 (range, 1.2-11,534). Nearly all were prescribed 50 Gy in 5 fractions (99%) and received neoadjuvant chemotherapy (93%). Less than half (43%) received post RT chemotherapy. A minority underwent resection after RT (15%). Most were non-diabetic (72%) with median BMI of 24.4 kg/m2 (range, 16.3-41.5) and ECOG of 0-1 (94%). Median SVR was 0.47 (range, 0.19 - 1.41). On univariate analysis, high SVR (HR 0.4, 95% CI 0.16-1.0, p=0.049) and surgery after RT (HR 0.4, 95% CI 0.2-0.82, p=0.012) were associated with improved OS while diabetes (HR 1.71, 95% CI 1.05 – 2.77, p=0.03) and ECOG 2+ (HR 2.96, 95% CI 1.13-7.79, p=0.028) were negatively associated. On multivariate analysis for OS, only post RT surgery was significant (HR 0.35, 95% CI 0.14-0.85, p=0.021) with SVR reaching near significance (HR 0.41, 95% CI 0.15-1.09, p=0.075). Surgery after SMART was singularly associated with improved PFS on univariate (HR 0.34, 95% CI 0.15-0.76, p=0.008) and multivariate (HR 0.32, 95% CI 0.12-0.84, p=0.02) analyses.
Conclusion:
High SVR is associated with improved OS in PDAC after SMART on univariate analysis with a trend toward significance on multivariate modeling. The absence of a PFS benefit may suggest an indirect anti-cancer mechanism for SVR. These findings support the use of MR-derived body composition metrics as prognostic biomarkers in PDAC patients undergoing SMART. Future studies are needed to determine whether visceral fat reduction enhances outcomes in this population.