Clinical Outcomes of Intraoperative Radiation Therapy, Postoperative Radiation Therapy, and Definitive Radiation Therapy for Non-Metastatic Pancreatic Cancer

To evaluate the usefulness of intraoperative radiotherapy (IORT) after tumor resection, postoperative radiotherapy (PORT), and definitive external beam radiotherapy for non-metastatic pancreatic cancer, the results of the three treatments were retrospectively analyzed. Ninety-nine patients with non-metastatic pancreatic cancer received radiotherapy between 1995 and 2014. Thirty patients received surgery and IORT, 31 patients received surgery and PORT, and 38 received definitive radiotherapy alone. Treatment policy was decided after discussion with attending physicians, surgeons, and patients. Tumor stage (UICC 2009) was I in 6, IIA in 14, IIB in 29, III in 42, and IVa in 8. The definitive radiotherapy group tended to have more advanced disease, while there were no differences in patient characteristics between the IORT and PORT groups. IORT was administered using 9-20 MeV electron beams, and the electron doses ranged from 20 to 30 Gy. The irradiation field included tumor bed with avoidance of the bowels. PORT was administered with 10-MV X rays, and the total doses ranged from 40 to 64.6 Gy with a daily fraction of 1.6-2.0 Gy. The treatment planning was made for 4-port or conformal radiotherapy using 3D-treatment planning systems. The treatment field basically included the tumor bed. Surgeons and radiation oncologists discussed the inclusion of regional lymph nodes in the treatment volume. Methods for definitive radiotherapy were the same as those for PORT, whereas the total dose ranged from 50.4 to 61.2 Gy. The treatment fields covered the primary tumor and regional lymph nodes. Associations between clinical parameters (age, sex, tumor site, performance status, stage, margin status at surgery, and use of gemcitabine) and local control/overall survival (OS) were analyzed using the log-rank test. The median follow-up period for all patients was 11 months (range, 1.1-145 months). The 2-year OS rate was 22% in the IORT group, 16% in the PORT group, and 6% in the definitive radiotherapy group. Stage and surgical margins were correlated with OS in the IORT group, and performance status and chemotherapy were correlated with OS in the PORT group and definitive radiotherapy group. Macroscopic tumors should be resected completely in IORT. Good PS and use of chemotherapy were significant factors that affected OS in PORT and definitive RT. Attentions should be paid to these factors in actual treatment. Anew clinical trial including radiotherapy is in the planning stage to evaluate the benefit of radiotherapy.