High-dose stereotactic body radiotherapy by real-time MRI guided tracking for locally advanced or recurrent pancreatic cancer: prospective single-center study

Abstract

Purpose: Real-time MR imaging during radiation allows for tumor tracking through breathing control. Using MR guided Radiotherapy (MRgRT) small margins can be used, allowing high doses to the tumor with respect to the surrounding radiation-sensitive organs in locally advanced- (LAPC) or recurrent pancreatic cancer (RePC). This study analyses clinical outcomes for unresectable LAPC and RePC after MRgRT. Method: Data of stereotactic MRgRT were collected prospectively in a IRB-approved database (May 2016-Dec 2020). MRgRT doses were 32-40 Gy in 4-5 fractions in two weeks, delivered during real-time breathing control. Results: In total, 91 pts (75 LAPC/16 RePC) were treated, all unresectable tumors. Median age was 69 years. Median tumor volume was 31.8 cm3. Initial treatment was chemotherapy in 80.2% (mainly FOLFIRINOX). Location was in the head(64.0%) and body/tail (36.0%). One year overall survival (OS) from start of MRgRT was 43.0% (median OS 10.4 months; 16.5 months from diagnosis). Age, performance status, baseline pain, tumor location and -volume significantly correlated with OS. Actuarial local control at 1 year was 72.4%, with RECIST stable disease in the vast majority. No variables correlated with local control. One year distant metastases free interval was 27.5% (median 6.9 months). Early toxicity included mild fatigue, pain, nausea or diarrhea. Three patients experienced grade ≥3 fatigue (3.3%), Late grade 3 duodenal toxicity was observed in three patients (3.3%). Conclusion: Real-time stereotactic MRgRT with breathing control is feasible with good local control and minimal toxicity in patients with unresectable LAPC and RePC. This option should be considered in multidisciplinary teams.