– PANCREATIC TUMORS Proton Radiotherapy for Isolated Local Recurrence of Primary Resected Pancreatic Ductal Adenocarcinoma

Background. The optimal treatment for isolated local recurrence (ILR) of pancreatic adenocarcinoma (PDAC) after surgical resection remains unclear. This study aimed to evaluate the safety and efficacy of proton radiotherapy (PRT) for ILR of PDAC after surgery. Methods. The medical records of patients with ILR of PDAC after surgery who underwent proton beam therapy between 2011 and 2015 at Hyogo Ion Beam Medical Center were retrospectively studied. Results. The study analyzed 30 patients (14 women and 16 men) with a median age of 65 years (range 38–81 years) who had initially undergone pancreatoduodenectomy (n = 23) or distal pancreatectomy (n = 7) for their primary tumors. Upon ILR, PRT was administered with a median total cumulative dose of 67.5 gray equivalent (GyE) (range 50–67.5 GyE) using 19 to 25 fractions. For 25 patients, concurrent chemotherapy was administered using gemcitabine (n = 18) or S-1 (n = 7). Four patients (13.3%) experienced acute grade C 3 gastrointestinal toxicities. After a median follow-up period of 17.6 months (range 2.1–50.4 months), 23 patients had experienced tumor progression and 10 had died. Nine patients (30%) experienced local tumor progression. The median overall, progression-free, and local progressionfree survival rates were 26.1, 12.3, and 41.2 months, respectively. Pre-PRT serum levels of cancer antigen 19-9 higher than 100 U/mL and duke pancreatic monoclonal antigen type 2 higher than 150 U/mL were significantly associated with shorter progression-free survival rates. Conclusions. Proton radiotherapy for ILR of PDAC after surgery is well tolerated and produces good locoregional control and should be considered for eligible patients. Despite recent advances in diagnostic and therapeutic strategies, the prognosis for patients with pancreatic ductal adenocarcinoma (PDAC) remains dismal. Only surgical resection is a potentially curative treatment. However, approximately 80% of patients with PDAC experience recurrences after surgery with curative intent. Of these patients, 20–30% experience locoregional recurrence without distant metastasis (i.e., isolated local recurrence [ILR]). To date, treatment strategies for these patients are not well established. Because up to 30% of patients with PDAC die of local destructive disease, those who experience ILR can achieve extended survival by controlling locoregional recurrence. Moreover, local recurrence may be symptomatic if it involves adjacent structures such as the abdominal nerve plexus or bile duct. Therefore, local treatments such as repeat resection or radiotherapy have been considered as therapeutic options for these patients. Proton radiotherapy (PRT), a type of particle radiotherapy characterized by the Bragg peak phenomenon, enables coverage of the tumor volume with high accuracy while the doses to surrounding normal tissue are reduced much more effectively than with conventional photon radiotherapy. Thus, proton therapy is of particular interest for patients with tumors located close to radiationsensitive organs such as the gastrointestinal (GI) tract or Society of Surgical Oncology 2019 First Received: 6 May 2018 H. Toyama, MD, PhD e-mail: tymhr@me.com Ann Surg Oncol https://doi.org/10.1245/s10434-019-07471-z