Using adaptive magnetic resonance image-guided radiation therapy for treatment of inoperable pancreatic cancer

Abstract

Background: Adaptive magnetic resonance imaging-guided radiation therapy (MRgRT) can escalate dose to tumors while minimizing dose to normal tissue. We evaluated outcomes of inoperable pancreatic cancer patients treated using MRgRT with and without dose escalation.

Methods: We reviewed 44 patients with inoperable pancreatic cancer treated with MRgRT. Treatments included conventional fractionation, hypofractionation, and stereotactic body radiation therapy. Patients were stratified into high-dose (biologically effective dose [BED10 ] >70) and standard-dose groups (BED10 ≤70). Overall survival (OS), freedom from local failure (FFLF) and freedom from distant failure (FFDF) were evaluated using Kaplan-Meier method. Cox regression was performed to identify predictors of OS. Acute gastrointestinal (GI) toxicity was assessed for 6 weeks after completion of RT.

Results: Median follow-up was 17 months. High-dose patients (n = 24, 55%) had statistically significant improvement in 2-year OS (49% vs 30%, P = 0.03) and trended towards significance for 2-year FFLF (77% vs 57%, P = 0.15) compared to standard-dose patients (n = 20, 45%). FFDF at 18 months in high-dose vs standard-dose groups was 24% vs 48%, respectively (P = 0.92). High-dose radiation (HR: 0.44; 95% confidence interval [CI]: 0.21-0.94; P = 0.03) and duration of induction chemotherapy (HR: 0.84; 95% CI: 0.72-0.98; P = 0.03) were significantly correlated with OS on univariate analysis but neither factor was independently predictive on multivariate analysis. Grade 3+ GI toxicity occurred in three patients in the standard-dose group and did not occur in the high-dose group.

Conclusions: Patients treated with dose-escalated MRgRT demonstrated improved OS. Prospective evaluation of high-dose RT regimens with standardized treatment parameters in inoperable pancreatic cancer patients is warranted.

Keywords: magnetic resonance imaging; pancreatic cancer; radiation therapy.

Conflict of interest statement

The authors listed below report the following financial relationships: NJ reports honoraria from ViewRay, outside the submitted work. LP reports honoraria and stock from ViewRay along with advisory role, speakers' bureau, and research funding from BTG, outside the submitted work. EAM reports travel accommodations from ViewRay, outside the submitted work. AB and FL report honoraria and travel accommodations from ViewRay, outside the submitted work. MCR reports travel expenses from Varian and BTG, outside the submitted work. MFB reports travel accommodations from ViewRay along with research funding from AstraZeneca outside the submitted work, outside the submitted work. PJP reports research funding from ViewRay, outside the submitted work. PL reports honoraria, consulting/advisory role, and travel accommodations from ViewRay, AstraZeneca, and Varian along with research funding from AstraZeneca, outside the submitted work. All other authors have no conflicts to declare.

© 2019 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Figures

Figure 1

Overall survival from start of radiation therapy stratified by biologically effective dose (BED10). Standard error bars displayed at each 6‐mo timepoint

Figure 2

Freedom from local failure from start of radiation therapy stratified by biologically effective dose (BED10). Standard error bars displayed at each 6‐mo timepoint