Towards online MRI guided radiotherapy for pancreatic cancer

Abstract

Pancreatic cancer is a devastating disease with a poor prognosis. Even after surgery with curative intent, life expectancy is poor. As the life span for these patients is limited, preventing deterioration of quality of life is exceedingly important. We found that most QoL items decrease after surgery for pancreatic cancer, to return to baseline values at 3 to 6 months. Patients with and without severe surgical complications experienced no differences in QoL up to 1 year after resection. For patients with locally advanced tumors, a non-invasive treatment with limited side effects and a positive effect on physical symptoms is desired. Radiotherapy for pancreatic cancer is challenging, as the pancreas moves with respiration. We analyzed this tumor motion with aid of cine MRI and found that these motion patterns highly differed between individual patients. This requires individualized strategies for motion management. When choosing for gated radiotherapy, this is best performed at the end-expiration position as this is the most stable position in the breathing cycle. In addition, we found that breathing induced motion can easily be reduced up to 40% by application of an abdominal corset. Another challenge in pancreatic radiotherapy is the poor visibility of tumor and OAR with the current gold standard CT. As MRI has a better soft tissue contrast, we developed contouring recommendations for contouring of pancreatic cancer and OAR with the aid of multiparametric MRI. The tumor volumes as contoured on MRI are smaller compared to volumes as contoured on CT in an interobserver study. Lastly, we studied MRI guided stereotactic radiotherapy in patients with unresectable pancreatic cancer, applying these new strategies. We found that stereotactic radiotherapy up to a dose of 24 Gy in 3 fraction is safe and feasible, but future research should focus on improving the clinical results. This might be achieved by a better patient selection, a higher radiation dose and a combination with effective chemotherapy.