Stereotactic body radiation therapy for locally advanced pancreatic cancer

Abstract

Purpose: Stereotactic body radiation therapy (SBRT) is a promising treatment modality for locally advanced pancreatic cancer (LAPC). We evaluated the clinical outcomes of SBRT in patients with LAPC.

Patients and methods: We retrospectively analyzed the medical records of patients with LAPC who underwent SBRT at our institution between April 2011 and July 2016. Fiducial markers were implanted using endoscopic ultrasound guidance one week prior to 4-dimensional computed tomography (CT) simulation and daily cone beam CT was used for image guidance. Patients received volumetric modulated arc therapy or intensity modulated radiotherapy using respiratory gating technique. A median dose of 28 Gy (range, 24-36 Gy) was given over four consecutive fractions delivered within one week. Survival outcomes including freedom from local disease progression (FFLP), progression-free survival (PFS), and overall survival (OS) were analyzed. Acute and late toxicities related to SBRT were assessed.

Results: A total of 95 patients with LAPC were analyzed, 52 of which (54.7%) had pancreatic head cancers. Most (94.7%) had received gemcitabine-based chemotherapy. The 1-year FFLP rate was 80.1%. Median OS and PFS were 16.7 months and 10.2 months, respectively; the 1-year OS and PFS rates were 67.4% and 42.9%, respectively. Among 79 patients who experienced failure, the sites of first failures were isolated local progressions in 12 patients (15.2%), distant metastasis in 55 patients (69.6%), and both in 12 patients (15.2%). Seven patients (7.4%) were able to undergo surgical resection after SBRT and four had margin-negative resections. Three patients (3.2%) had grade 3 nausea/vomiting during SBRT, and late grade 3 toxicity was observed in another three patients.

Conclusions: LAPC patients who received chemotherapy and SBRT had favorable FFLP and OS with minimal treatment-related toxicity. The most common pattern of failure was distant metastasis, which warrants further studies on the optimal scheme of chemotherapy and SBRT.

Fig 1. Protocol for marker-guided gated volumetric-modulated arc therapy.

The protocol consists of two steps—pre-treatment and in-treatment. (a) Pre-treatment: patient alignment and image guidance are performed. If alignment is significantly out of range at each procedure, patient alignment is performed again. (b) In-treatment: after delivering the first arc dose, the half-time fiducial markers are verified.

Fig 2

Kaplan-Meier curves of (a) freedom from local disease progression, (b) overall survival, and (c) progression-free survival in the study population.