# The Value of Stereotactic Radiotherapy After FOLFIRINOX in Patients with Pancreatic Cancer with Vascular Contact—A Nationwide, Retrospective Cohort Study

## TL;DR

This study found that adding stereotactic radiotherapy after chemotherapy did not improve survival in pancreatic cancer patients, but it showed better tumor characteristics in those who had surgery.

## Contribution

The study is the first nationwide retrospective analysis showing no OS benefit from SBRT after FOLFIRINOX, but improved histopathological outcomes in resected cases.

## Key findings

- Stereotactic radiotherapy did not improve overall survival in patients with pancreatic cancer after chemotherapy.
- In resected patients, SBRT was linked to better histopathological outcomes like ypT0-2 and ypN0.
- Landmark analysis showed no OS difference between SBRT and no SBRT groups after 12 months.

## Abstract

Pancreatic cancer with vascular contact without distant metastasis is treated with chemotherapy. In addition, stereotactic radiotherapy has been used following chemotherapy in an attempt to increase progression-free and overall survival. However, the benefit of radiotherapy in improving local disease control or overall survival is not known. In the current study, in patients who did not develop progressive disease after at least four cycles of (modified)FOLFIRINOX, stereotactic radiotherapy was not associated with improved overall survival compared to chemotherapy-only treatment. In the subgroup of patients who underwent resection, stereotactic radiotherapy was associated with favorable histopathological characteristics.

Background/Objectives: Stereotactic body radiotherapy (SBRT) aims to prolong overall survival (OS) in patients with pancreatic ductal adenocarcinoma (PDAC) with vascular contact without progression of disease after (m)FOLFIRINOX. The primary objective of this study was to determine the potential value of SBRT. Methods: This nationwide, retrospective cohort study included patients with PDAC without progression of disease after at least four cycles of (m)FOLFIRINOX. The study comprised two cohorts, the SBRT and the No SBRT group. A landmark analysis excluded patients with a follow-up or OS time less than 12 months to minimize immortal time bias in the SBRT group. The primary outcome was OS from diagnosis. Secondary outcomes were the histopathological characteristics after resection. Results: Overall, 331 patients were included, of whom 231 were in the landmark analysis. In the overall cohort, the median OS was 20.7 months in the SBRT group versus 15.7 months in the No SBRT group (p = 0.004). In the landmark analysis, the median OS was 23.2 months in the SBRT group compared to 22.3 months in the No SBRT group (p = 0.554). These results indicate the presence of immortal time bias in the overall cohort in favor of the SBRT group. In the subgroup after resection, ypT0-2 (95% versus 76.5% [p = 0.026]), ypN0 (75% versus 37.3% [p < 0.004]), and absence of perineural invasion (50% versus 68.6% [p = 0.015]) were more prevalent in the SBRT group. Conclusions: In a landmark analysis, including only patients who survived at least 12 months after diagnosis, we found no difference in median OS between (m)FOLFIRINOX-only and (m)FOLFIRINOX with consecutive SBRT.