# CT imaging findings following treatment with combination SBRT and chemotherapy versus stand-alone chemotherapy for locally advanced pancreatic adenocarcinoma

## TL;DR

This study compares CT imaging changes in pancreatic cancer patients treated with SBRT plus chemotherapy versus chemotherapy alone, finding that certain changes may reflect treatment effects rather than disease progression.

## Contribution

The study identifies treatment-related imaging changes in combination SBRT/chemotherapy for pancreatic cancer that may be mistaken for disease progression.

## Key findings

- SBRT/chemotherapy patients showed significantly increased vascular involvement over time compared to chemotherapy-only patients.
- Peripancreatic fat stranding increased significantly in the SBRT/chemotherapy group but not in the chemotherapy-only group.
- These imaging changes are likely treatment-related effects rather than signs of disease progression.

## Abstract

To evaluate imaging findings of patients with locally advanced pancreatic cancer (LAPC) following treatment with combination stereotactic body radiotherapy (SBRT) and chemotherapy versus stand-alone chemotherapy.

This retrospective study included patients with LAPC who received combination SBRT/chemotherapy versus those that received stand-alone chemotherapy from 2005 to 2018. Comparisons were made pre-treatment and at four standardized post-treatment intervals (1 month, 3–6 months, 7–12 months, greater than 12 months) in patients without disease progression. Imaging variables included degree of vascular involvement graded on a standardized scale and peripancreatic fat stranding. A p-value < 0.05 was considered significant.

A total of 96 patients were included, 64 patients (37 men; mean age, 68 ± 11 years) treated with SBRT/chemotherapy and 32 patients (17 men; mean age, 69 ± 10 years) treated with stand-alone chemotherapy. Increased vascular involvement over time in the absence of disease progression was significantly higher in the SBRT/chemotherapy group (17%) versus the stand-alone chemotherapy group (9%), p = 0.004 (95% CI 2–12%). Peripancreatic fat stranding increased over time in the SBRT/chemotherapy group being present in 29/64 (45%) patients on the pre-treatment computed tomography (CT) versus 55/64 (86%) patients on the last recorded CT, p < 0.001 (McNemar OR = 14, 95% CI 3.3–58.8). No significant change in peripancreatic fat stranding over time was noted in the stand-alone chemotherapy group being present in 9/32 (28%) patients on the pre-treatment CT and 7/32 (22%) patients on the last imaging recorded, p = 0.45 (McNemar OR = 2, 95% CI 0.4–10.9).

Increased vascular involvement and peripancreatic fat stranding over time in LAPC patients treated with combination SBRT/chemotherapy should be a potential anticipated treatment-related effect, not necessarily indicating disease progression.